UnB/IG - DISSERTAÇÕES E TESES DE OUTROS CURSOS
DE PÓS-GRADUAÇÃO NO BRASIL

cpggeo/Curso de Pós-Graduação em Geociências - UFRGS
MSc THESES - MARINE GEOLOGY - (this page)
Dissertações de Mestrado GEOLOGIA MARINHA -(esta página)

[MSc Theses(Stratigraphy) ]
[MSc Theses(Geochemistry) ]
[MSc Theses(Paleontology) ]
[PhD Theses ]

SEDIMENTOLOGIA DO CANAL DE RIO GRANDE

SEDIMENTOLOGY OF THE RIO GRANDE CHANNEL

Inês Leonida da Rosa Martins (1971)

Adviser: Luiz Roberto Silva Martins

Abstract

The Lagoa dos Patos inlet bottom sediments were studied by means of their textural properties.

On this base, the inlet can be divided into three distinct sedimentary environments:

1) Lagoonal, the most interior, predominantly silty, sometimes argillaceous sediments;

2) Transitional, medium position, consisting of variable mixtures of sand and fine sediments, within a range of silty clay, sandy silt and clayey silt, characterizing the meeting of two sedimentary domains;

3) Marine, external position, with a more expressive energy level, characterized by well­sorted fine sands, with textural properties very similar to the adjacent oceanic beach sands.

O QUATERNÁRIO DA REGIÃO NORTE DA PLANÍCIE COSTEIRA DO RIO GRANDE DO SUL - BRASIL

THE QUATERNARY OF THE NORTHERN REGION OF THE RIO GRANDE DO SUL COASTAL PLAIN - BRAZIL

Hardy Jost (1971)

Adviser: Luiz Roberto Silva Martins

Abstract

Results of a systematic study based on surface mapping of the northern region (between latitudes 29°15' and 31°S) of the Rio Grande do Sul Coastal Plain, South Brazil, are presented and discussed.

Surface mapping and cross­ ­sections showed that this area contains the following main events:

- a progressive overlap of continental deposits over marine Miocene deposits of the Pelotas Basin. This overlap is represented by 250m of continental sediments known as Graxaim Formation;

- a marine progressive overlap, that partially covers the Graxaim Formation, and whose deposits are known as Chui Formation. This unit comprises a complete transgressive­ ­regressive sedimentary sequence. During the transgression the sea level rised up to 15m above the present level;

- this transgression was responsible for a morphologic transformation of the coast, developing bays and "Rias" from parallel 30°15'S to the north. In one region the low altitudes allowed the ocean to invade the continent deeply, originating a bay environment;

- during the regression, successive dune strings developed and are known as Itapoã Formation; the upper section of the Chui Formation (marine) was deposited, and the bay environments received fluvial deposits developing the Guaiba Formation;

- the "Porto Alegre Basin" is a tectonic unit defined in this report.

Semi­arid climatic conditions, alternating with humid periods, prevailed during the whole Pleistocene, and probably during the Miocene­Pliocene and part of the Holocene, as it could be deduced from paleosoils, paleopavements and their relations with the lithostrati-graphic units of the area.

The lithologic characterization of each stratigraphic unit is presented. The Graxaim Formation comprises a conglomeratic facies related to alluvial fans deposition, and a silty­sand facies probably deposited along a coastal "bajada". The Chui Formation is built up of near shore sand deposits, and along the surface this unit is entirely represented by emersion sands. The Guaiba Formation is represented by a conglomeratic facies (alluvial fans and deltas), and a sandy facies (alluvial plain and bay deposits). The Itapoã Formation comprises a series of sand strings deposited by eolean action along the coast, at successive stationary sea levels during the Pleistocene and Holocene.

The author emphasizes the still remaining problems that must be studied and solved for a better understanding of the whole Coastal Plain region.

All the elements of this research are proposed as modifications to the stratigraphic and lithologic studies made by Delaney (1965) in the same region.

SEDIMENTOLOGIA DA FORMAÇÃO TUPANCIRETÃ

SEDIMENTOLOGY OF THE TUPANCIRETÃ FORMATION

Egydio Menegotto (1972)

Adviser: Luiz Roberto Silva Martins

Abstract

Field and laboratory studies showed that the Tupanciretã Formation in the State of Rio Grande do Sul, Brazil, consists mainly of fine to very fine sandstones, silty sandstones, and conglomerates restricted to the Southern part of the studied area. The research evidenced the existence of a sand facies located between Júlio de Castilhos and Cruz Alta.

Although not abundant, the structures are represented by tabular cross­bedding deeping to NE and E and few occurrences of cut­and­fill (through) bedding.

Results of mechanic analyses showed that these sediments present a high number of textural classes, high standard deviation, mean size between 2 and 4 Ø, with positiveskewness and lepto­ to mesokurtic distributions. Morphoscopic aspects are characterized by high sphericity, sub­rounding, and kidney­shaped polished surface texture. Light mineral is chiefly quartz, heavy minerals are mainly magnetite, turmaline, and zircon, and the most abundant clay mineral is kaolinite.

The origin of these sediments is fluviatile, accumulated by meandric rivers. Their source area consisted of basaltic rocks, which supplied the coarser components of the conglomerates, and sedimentary rocks situated in the region known as "Depressão Central".

Tectonic events raised and deepened the whole area westward, thus allowing the establishment of the present drainage.

DINÂMICA EÓLIA NA ILHA DE SANTA CATARINA

EOLIAN DYNAMICS IN THE SANTA CATARINA ISLAND

Vera Maria Leal Podolsky (1972)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation aims at studying the eolian dynamics of Santa Catarina Island. The relationships of granulometry and morphoscopy were studied considering the three faces of the dune: crest, lee and stoss sides, from the point of view of size and classification.

At the same time, studies were made to compare the eolian dynamics and the other sedimentary dynamics of the areas adjacent to the dunes.

Regarding the granulometry, it was observed that the mean size of the material of the dune is situated in the "fine sand" group, with very well­classified sediments, presenting a small number of textural classes and a clearly positive skewness.

The lagoon material is situated in the "medium sand" group; thesediments are well­classified and present a predominantly negative skewness.

The sediments of the ocean beach range from "coarse to fine sand"; the classification of the sediments varies from good to moderate and they present alternate skewness (positive/negative), with a predominance of the negative sign.

As to the morphoscopic aspects of the studied sediments, most of the diversity was found in the superficial texture between the eolian and beach environments; in the first there was a predominance of polished grains for all sizes and in the latter there was an oscillation, so that the smaller grains show a polished texture, and the greater ones a dominant polished smooth texture.

O ESTUÁRIO DO GUAÍBA:  CARACTERÍSTICAS TEXTURAIS, MINERALÓGICAS E MORFOLÓGICAS

THE GUAÍBA ESTUARY:  TEXTURAL, MINERALOGIC AND MORPHOLOGIC CHARACTERISTICS

Roberto Cunha (1972)

Adviser: Luiz Roberto Silva Martins

Abstract

Based on textural and mineralogic studies of bottom samples collected in the Guaiba Estuary, Rio Grande do Sul, Brazil, the author defines four estuarines facies: sandy facies, divided into coarse, medium and fine sub­facies; sandy­silt facies; silty­sand facies; and sandy­silty­clayey facies. Each one is thought to be the result of a mixture and deposition of solids provided by four different source areas, which range in time from Pre­Cambrian up to the Quaternary.

Clay mineralogical studies in the estuary show a significant relationbetween clays and the source areas, and the Pre­Cambrian chlorite and kaolinite, the montmorillonite from the Graxaim Formation, and the kaolinite resulting from the erosion of the Pleistocenic ferralitic soil of the Serra de Tapes Laterite are discussed.

Comparison with sedimentary patterns from other similar environments throughout the world are made, indicating the great influence of the borderland areas on the distribution of the bottom sediments.

OBSERVAÇÕES EM CÚSPIDES PRAIAIS NO LITORAL NORTE DE SANTA CATARINA

OBSERVATIONS ON BEACH CUSPS IN THE NORTHERN LITTORAL OF SANTA CATARINA

Beatriz Beck Eichler (1971)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation represents a study of the main grain characteristics of the beach sediments in the northern part of Santa Catarina between Porto Belo and Itajubá. Among the outstanding features, the beach cusps are specially mentioned and the most important relations of grain texture are established for this feature.

In this regard, the most diagnostic size parameter is the arithmetic mean (Mz), which showed higher granulometry on ridges than on the small embayments that give form to this feature.

The remaining statistical values show a great similarity for both regions, however with clearly coast features.

The morphoscopic characters indicate rates of 0.5 up to 0.7 on sphericity and round to well­rounded grains, and predominant polished rounded grain surface of the sand studied, not showing any variation between ridges and embayments.

Some aspects of construction, maintenance, and dimensions, as well as some considerations on the building or erosional characteristics of these features are also presented.

CONTRIBUIÇÃO À GEOLOGIA DO HOLOCENO DA PROVÍNCIA COSTEIRA DO RIO GRANDE DO SUL - BRASIL

A CONTRIBUTION TO THE HOLOCENE GEOLOGY OF THE COASTAL PROVINCE OF RIO GRANDE DO SUL - BRAZIL

Jorge Alberto Villwock (1972)

Adviser: Luiz Roberto Silva Martins

Abstract

The Southern Brazilian coastal area, defined as Rio Grande do Sul Coastal Province, is composed of two major geologic elements: Basement and Pelotas Basin. The former is constituted by the Pre­Cambrian Cristaline Complex and by the Palaeozoic and Mesozoic sedimentary and volcanic sequences of the Paraná Basin. During the Triassic, when this basement was acting as an instable platform; the latter, a marginal basin, was originated by faulting.

The sedimentary sequence which was accumulated in that basin results from successive transgressions and regressions early controlled by the balance of subsidence and sedimentation rates. Later, from Pleistocene to recent times, they depended on the glacio­eustatic oscillations which took place along the Cenozoic Era.

The Holocene sedimentary cover that lies over them needs to be considered as another important geologic element in that coastal province. It makes up all the major morphographic features which are responsible for the present superficial configuration of that area. That sequence is constituted by a transregressive bed whose upper portion is exposed on the coastal sandy plain. There one can find many discontinuous lithostratigraphic units, variable in age from place to place, as a result of the displacement of different sedimentation environments over the same area. The geological history of that coastal sandy plain could be determined by means of a detailed geomorphological analysis.

The coastal sandy plain which keeps apart the Patos Lagoon from the Atlantic Ocean, is composed of a series of four connected barriers and was defined as Patos Lagoon Multiple Barrier. The origin of this multiple barrier is directly related to the eustatic oscillations which took place in that region during the last 6,000 years, after the end of the Flandrian Transgression.

The first barrier began when the sea level was in its higher position, at the end of the great Holocene transgression. It was built over a series of bay mouth bars and spits which had been constructed along the submergence coast of that time. Wind­blown sand taken from the shores during minor variations in the sea level was accumulated over them, making the barrier wider and higher.

Three more barriers were built on the coast, each one beginning through the emergence of longshore bars during the successive and alternated regressive and transgressive periods which have been occurring in the last thousand years.

The accumulation of large quantities of sand along this time, without any tectonic activity in the area, caused a progradation of the coast (depositional regression). Most of this sand was brought from offshore and was piled on the shore from where it was wind­blown to the barrier.

All these data suggest that the Rio Grande do Sul coast is a barrier type, secondary coast, according to Shepard's classification of coast lines.

The essay of correlation of the eustatic oscillations obtained by means of the geomorphological interpretation of that area with the Fairbridge's sea level eustatic variations curve for the last 6,000 years showed a lot of coincidences, but it will be necessary more radiocarbon data to obtain trustworthy results.

In spite of everything, the evolutive sketch proposed here may be used as a workable hypothesis in the study of all the remnant Holocene terrains of the Rio Grande do Sul Coastal Province. It may be useful in the chrono­stratigraphic organization of the various sedimentary units that one can find there.

GEOLOGIA DOS DEPÓSITOS CALCÁRIOS BIODETRÍTICOS DA PLATAFORMA CONTINENTAL DO RIO GRANDE DO SUL

GEOLOGY OF THE BIODETRITAL CALCAREOUS DEPOSITS OF THE RIO GRANDE DO SUL CONTINENTAL SHELF

Alberto Garcia de Figueiredo Jr. (1975)

Adviser: Luiz Roberto Silva Martins

Abstract

The morphology of the inner continental shelf off Rio Grande do Sul State, Brazil, is generally quite smooth. However, in some places it displays sand bodies of Holocene age that are sometimes connected to the shoreline and sometimes isolated from it.

Elongated deposits of biodetrital material also occur on the shelf in association with these Holocene sandy bodies. These biodetrital deposits have been interpreted in the past as representing fossil shorelines. We suggest that these biodetrital deposits may not be fossil shorelines but may have been formed in response primarily to the hydrodynamics of the inner shelf. The hydrodynamics of the inner shelf is also responsible for the development and orientation of the sandy bodies.

This paper is based on the study of the ecology of Mollusca contained in these biodetrital deposits, associated beachrocks, C­14 dates, a study of the submarine morphology, shallow structure, currents and sediment transport in the area.

GEOLOGIA DO CANAL DE SANTA CRUZ E PRAIA SUBMARINA ADJACENTE À ILHA DE ITAMARACÁ - PE

GEOLOGY OF THE SANTA CRUZ CHANNEL AND SUBMARINE BEACH ADJACENT TO ITAMARACÁ ISLAND - PE

Luiz Gonzaga Gomes Lira (1975)

Adviser: Luiz Roberto Silva Martins

Abstract

Though being not an exhaustive account on the several features of the Santa Cruz Channel, its affluent rivers and the submarine beach surrounding the Itamaracá Island (Pernambuco State), this dissertation tried to draw a sedimentological panorama of the area under study. Accordingly, the biotic, sedimentologic, geochemical, chemical and dynamic characteristics were analyzed and the ecological implications emphasized.

It is hoped that the results of this research, when utilized by future students of the ecological characteristics of the area, will assure them that Geology is an important tool for studying the living forms of the aquatic environment. Only then the aim of the present study shall be totally accomplished.

CONTRIBUIÇÃO À SEDIMENTOLOGIA DA PLATAFORMA CONTINENTAL BRASILEIRA ENTRE FORTALEZA E RECIFE

CONTRIBUTION TO THE SEDIMENTOLOGY OF THE BRAZILIAN CONTINENTAL SHELF BETWEEN FORTALEZA AND RECIFE

Eloy Lopes Loss (1975)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation aims to adding some data to the studies of superficial sediments of the Brazilian Continental Shelf between the cities of Fortaleza (Ceará State) and Recife (Pernambuco State).

Supplementary geologic, tectonic and hydrographic studies of the continent in front of the Shelf were developed. In addition, comments on coastal classifications and morphological characteristics of the Shelf were made.

The mechanical analysis of the superficial sediments gathered during the Cruzeiro Águas Rasas Operation (REMAC Project, tracts 4,5,6,7) made it possible the computer­programed establishment of four statistical parameters correspondent to the four characteristic moments of a sedimentary distribution. The textural classification allowed to identify the several sedimentary facies present.

Maps of median variation, arithmetic mean, standard deviation, assimetry and kurtosis were built for a better elucidation of the distributions.

The examination of the obtained elements permitted to characterize a larger occurrence of the biogenic­ -biodetritic sediments in the Brazilian Continental Shelf between Fortaleza and Recife.

CONTRIBUIÇÃO À SEDIMENTOLOGIA DA PLATAFORMA CONTINENTAL BRASILEIRA ENTRE SALINÓPOLIS E FORTALEZA

CONTRIBUTION TO THE SEDIMENTOLOGY OF THE BRAZILIAN CONTINENTAL SHELF BETWEEN SALINÓPOLIS AND FORTALEZA

Ely Alberto Dehnhardt (1975)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation deals with the surface sediments of the Brazilian Continental Shelf between Salinópolis and Fortaleza. Hydrography and the diversification of the littoral in the area under study as well as size variation of the particles (according to statistical standards) were also taken into consideration.

The analyzed samples were collected at tracts 5 and 6 of the Projeto Remac do Cruzeiro "Águas Claras" and processed at the Center for Coastal and Oceanic Geological Studies (CECO), Federal University of Rio Grande do Sul.

It was found that these sediments have a predominantly terrigenous origin, owing to the contribution of an intense and perennial drainage; towards the edge of the shelf, it progressively incorporates terrigenous­marine sediments and, finally, biodetritic marine sediments are found at the edge.

MORFOLOGIA, ESTRATIGRAFIA, ESTRUTURA E EVOLUÇÃO DO PLATEAU DE SÃO PAULO (MARGEM SUDESTE BRASILEIRA) E IMPLICAÇÕES PARA A HISTÓRIA INICIAL DO ATLÂNTICO SUL

MORPHOLOGY, STRATIGRAPHY, STRUCTURE AND EVOLUTION OF SÃO PAULO PLATEAU (SOUTHEASTERN BRAZILIAN MARGIN) AND IMPLICATIONS FOR THE EARLY HISTORY OF SOUTH ATLANTIC

Luiz Antônio Pierantoni Gambôa (1976)

Adviser: Naresh Kumar e Luiz Roberto Silva Martins

Abstract

The São Paulo Plateau is a prominent marginal plateau in the southeastern Brazilian margin. It is bounded on the north and south by fracture zones and appears to be situated on oceanic crust which was created between the Neocomian and Aptian. This marginal plateau is underlain by 1 to 2 km of Albian­ -and­younger terrigenous and calcareous sediments which overlie 2 to 3 km of Aptian evaporites. The stratigraphy of the plateau has been inferred through correlation of seismic­reflection profiles with the drilling data from Site 356 (DSDP) located on the southeastern corner of the plateau. Direct correlation of this stratigraphy is possible with the stratigraphy of the Santos Basin, a shelf basin located adjacent to the plateau. A continuous evaporitic layer of Aptian age extends from the basin to the plateau. In the Albian, shallow­platform limestones were deposited in the basin, while open­marine limestones were deposited on the plateau. Coarse conglomerates were deposited in the basin during the Turonian­Coniacian time, whereas distal turbidites were contem-poraneously deposited on the plateau. A major transgression in the Maestrichtian trapped the terrigenous sediments within the Santos Basin and halted terrigenous sedimentation on the plateau. Cenozoic sediments in both areas are open marine. The sedimentary history of the Santos Basin and the São Paulo Plateau thus suggests that the two regions have been structurally continuous at least since the Late Cretaceous. The region occupied by the plateau has acted as a depocenter and has evolved as a marginal plateau since the termination of evaporitic deposition in the South Atlantic.

MINERALOGIA DAS AREIAS DE PRAIA ENTRE RIO GRANDE E CHUÍ - RIO GRANDE DO SUL

MINERALOGY OF THE BEACH SANDS BETWEEN RIO GRANDE AND CHUÍ - RIO GRANDE DO SUL

Maria Augusta Martins da Silva (1976)

Adviser: Luiz Roberto Silva Martins

Abstract

The foreshore and backshore sands between Rio Grande and Chuí are predominantly composed of quartz, but in some places heavy­ ­mineral concentrations appear as dark patches on the backshore surface. Opaques (ilmenite, magnetite, leucoxene, limonite) are the predominant minerals followed by epidote, augite, hypersthene and hornblende. Minor quantities of tourmaline, staurolite, garnet, rutile, kyanite, andalusite and nonazite are also present. The minerals show two associations: the first one in the north of the area where epidote, augite, hypersthene and hornblende predominate; the second in the south where the opaques predominate. The primary source of the heavy minerals was the igneous and metamorphic rocks of the Sul­Rio­Grandense Shield and the basalts from the Serra Geral Formation. They were incorporated in the coastal sediments during the Quaternary eustatic changes in sea level and, with the coastal plain evolution, they were spread over the beaches. At the present time, the fluvial contribution of heavy minerals is insignificant because most of the river sediment is trapped in the lagoons which parallel the shore. A small part of fluvial material reaches the ocean through the Rio Grande channel, probably influencing the basic character of the northern heavy­mineral association. The inner continental shelf, underlain predominantly by relict sands, is the main nowadays source of the shoreline sediments. The La Coronilla headland and Chuí cliff are also sources of minerals to the southern association. The deposits were originated by three concentration mechanisms: one related to the swash and backwash in stormy weather or during the strongest tides; another one caused by the development on the backshore of tidal ponds and/or channels; and the last one related to eolian winnowing action. The concentrates occur principally between Albardão ligthouse and Chuí village, where the black sands extend for some tens of kilometers. The concentrations near Chuí reach up to 47% by weight, the opaques represent 72% of the concentrate, 58.4% of which are ilmenite.

Rutile and zircon show maximum values between 5 and 6% and monazite occurs only as traces.

SEDIMENTOLOGIA E ESTRATIGRAFIA DO QUATERNÁRIO DO BAIXO VALE DO RIO ITAJAÍ­MIRIM (SANTA CATARINA)

QUATERNARY SEDIMENTOLOGY AND STRATIGRAPHY OF THE ITAJAÍ­MIRIM RIVER LOWER VALLEY (SANTA CATARINA)

Rosemari Dora Becker (1976)

Adviser: João José Bigarella

Abstract

The main purpose of the present Master Dissertation is devoted to the description and interpretation of the several degradational (pediment) and aggradational (gravel terrace) levels found in the lower Itajaí­Mirim valley.

With this in mind, a series of analyses were made. They included the textural (grain size and morphoscopy) and structural (pebble long axis attitude) characteristics of the Itaipava Formation and Canhanduba Member gravel deposits. The former occurs along the Itajaí­Brusque highway, while the latter is found at the locality of Canhanduba, in a road cut of the BR­101 near the city of Itajaí.

The grain size analysis and the structures of the deposits indicated that the sequences were laid down under torrential regime in which the paleoclimatic conditions were completely different from the present ones.

The sedimentary assemblage represented by the Itaipava Formation indicates the past alternation of two main group of processes. One caused the lateral degradation of the terrain followed by sedimentation. The other was responsible for the vertical dissection originating the erosive unconformities or diastems separating sedimentary sequences.

The statistical study of the attitude of the pebbles shows that at times the direction of the long axis was normal to the precious flow inside the paleovalley. This demonstrates that the pebble was rolling with its long axis perpendicular to the flow sense. When the flow stopped there was no time for the pebble to imbricate upstream. In other occasions, with more continuous flow, there was enough time and good conditions to the once rolling pebble to achieve an upstream imbrication.

In general, the measurements showed that all positions are between the transversal and the parallel attitude in relation to the paleovalley orientation.

The study of the deposits suggests and confirms the presence of semiarid (concentrated rainfall) epochs alternating with humid ones (better distributed rainfalls) in the past.

DINÂMICA SEDIMENTAR DAS AREIAS DA PLATAFORMA CONTINENTAL DO RIO GRANDE DO SUL E POSSIBILIDADES DE SEU APROVEITAMENTO ECONÔMICO

SEDIMENTARY DYNAMICS OF THE SANDS FROM THE CONTINENTAL SHELF OF RIO GRANDE DO SUL AND THEIR POSSIBILITIES OF ECONOMIC UTILIZATION

Loreci Gislaine de Oliveira Lehugeur (1977)

Adviser: Luiz Roberto Silva Martins

Abstract

According to specific bibliography on the matter, the sand and gravel in the continental shelf are the largest exploitable superficial mineral resources.

The present dissertation deals with the sand deposits found in the Continental Shelf of Southern Brazil, approached from a dynamic and economic point of view.

A detailed analysis of the mechanic, morphoscopic and physical properties of the samples existent in the above­mentioned area was carried out with the purpose of confirming the possibility of using sand deposits as a source of great economic gains.

MINERAIS PESADOS DA PLATAFORMA CONTINENTAL DO RIO GRANDE DO SUL

HEAVY MINERALS OF THE CONTINENTAL SHELF OF RIO GRANDE DO SUL

Luiz José Tomazelli (1977)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation deals with the study of heavy minerals (granulometric fraction 2­3 Ø) of 81 surface sediment samples collected at the Rio Grande do Sul Continental Shelf, Brazil.

Heavy minerals constitute a small part of the studied sand fraction (the mean percentage is about 1%). The principal species are: magnetite, ilmenite, hornblende, augite, hypersthene, tourmaline, epidote, staurolite, kianite, garnet, zircon, rutile and sillimanite.

These minerals define four associations that characterize four heavy mineral provinces: (1) Inner Rio­grandense Province; (2) Patos Province; (3) Outer Rio­grandense Province and (4) Platina Province. In regard to geographic distribution, age and provenance, each of these provinces form a unit.

Two directions of sediment input were identified: (1) offshore direction, which supplies the Inner Rio­grandense, Outer Rio­grandense and Patos Province, and (2) south­north direction, which supplies the Platina Province.

ESTRUTURA RASA DO TALUDE E SOPÉ DA MARGEM CONTINENTAL DO RIO GRANDE DO SUL E URUGUAI

SHALLOW STRUCTURE OF THE CONTINENTAL SLOPE AND RISE, CONTINENTAL MARGIN OF RIO GRANDE DO SUL AND URUGUAY

Eliane da Costa Alves (1977)

Adviser: Carlos Maria Urien

Abstract

Seismic data along the Rio Grande do Sul and Uruguai continental margins revealed a thick wedge of sediments belonging to the Pelotas Basin and to the southern part of the Santos Basin. This wedge is identified in refraction records as a 1.8 km/sec seismic velocity layer.

The deposition of the wedge was initiated during the Upper Miocene and continued through the Pleistocene. Alternating periods of deposition and erosion, owing to eustatic sea level fluctuations, caused the development of four distinct sedimentary sequences.

The distribution of the centers of maximum deposition of each of the sedimentary units suggests an overall progressive migration of the source towards the continent, probably because of marine transgression.

The accumulation of the sedimentary sequences within the 1.8 km/sec interval was responsible for the major physiographic features present in the study area. Of these, the Rio Grande cone is the most striking. Its construction took place mainly during the first depositional cycle, between the Upper Miocene and Lower Pliocene, forming a 900m thick depocenter. Later sequences were deposited over the distal portions of this depocenter.

The Rio Grande cone was active until the Late Wisconsin, with sedimentation rates averaging 20 cm/10³ years. This value was at least four times greater than Holocene rates.

During the Mid and Late Wisconsin, when lowered sea level prevailed, the continental shelf edge suffered erosion resulting in the truncation of the prograding sediments. The eroded material was fed to the Rio Grande cone via suspension and/or gravitational processes.

Since the Holocene transgression, the southern Brazil continental margin has not received any significant amount of terrigenous contribution. Two processes are still active: widespread pelagic sedimentation and geostrophic

contour current activity along the lower continental rise.

CONTRIBUIÇÃO À SEDIMENTOLOGIA DA PLATAFORMA CONTINENTAL BRASILEIRA ENTRE CABO FRIO (RJ) E RECIFE (PE)

CONTRIBUTION TO THE SEDIMENTOLOGY OF THE BRAZILIAN CONTINENTAL SHELF BETWEEN CABO FRIO (RJ) AND RECIFE (PE)

Tânia Hofmeister (1977)

Adviser: Luiz Roberto Silva Martins

Abstract

The present dissertation deals with the characterization of the superficial sediments of the Brazilian Continental Shelf between Cabo Frio (Rio de Janeiro State) and Recife (Pernambuco State), taking into consideration the granulometric variation and the analysis of the statistic parameters, in order to establish the main types of textural facies.

Geological, hydrological and climatological studies of the continent in front of the Shelf were developed; an evaluation of the physical and chemical oceanographic aspects of the water masses as well as of the bottom morphology of the Continental Shelf is also presented.

ASPECTOS SEDIMENTARES DA PLATAFORMA CONTINENTAL INTERNA DO RIO DE JANEIRO, ENTRE SAQUAREMA E PONTA NEGRA

SEDIMENTARY ASPECTS OF THE INNER CONTINENTAL SHELF OF RIO DE JANEIRO, BETWEEN SAQUAREMA AND PONTA NEGRA

Vera Regina Abelin Ponzi (1978)

Adviser: Luiz Roberto Silva Martins

Abstract

The main purpose of the present dissertation is to show the prominent aspects of the sedimentation dynamics, as well as the bottom morphology of the inner continental shelf off north littoral of Rio de Janeiro State, Brazil.

This paper presents a study of analytical data from 134 bottom samples, collected during hydrographic missions along the Brazilian continental shelf, carried out by the Diretoria de Hidrografia e Navegação (DHN) of the Brazilian Navy.

The sedimentary texture, dominated by sand facies, was determined through grain­size statistical parameters (mean diameter, standard deviation, skewness and kurtosis), furnished on IBM computer list.

The compositional characteristics of the sediments (quartzose and bioclastic sands) were based on the binocular examination of the sand fraction and estimates were made through the volume percentages of the significant constituents.

The quartz grains percentage is extremelly high and some grains are covered by iron oxide.

The biodetritic sands, composed entirely of calcium carbonate, are rich in shell fragments, bryozoans and foraminifers.

The morphoscopic features of the quartz grains reveal good roundness and sphericity, and polished and frosted mamillared surface texture.

The very worn and degraded nature of carbonate fragments and oxidized surface of quartz grains suggest that these sediments are of a relict nature, deposited during lower stands of sea level.

The local continental shelf sediments and morphology were widely affected by sea level fluctuations during the Quaternary. These fluctuations sculptured important features on the bottom relief, with a series of constructive or erosive shapes (terraces).

MORFOLOGIA E SEDIMENTOLOGIA DA PLATAFORMA CONTINENTAL ENTRE SÃO PAULO E SANTA CATARINA

MORPHOLOGY AND SEDIMENTOLOGY OF THE CONTINENTAL SHELF BETWEEN SÃO PAULO AND SANTA CATARINA

Iran Carlos Stalliviere Correa (1978)

Adviser: Luiz Roberto Silva Martins

Abstract

The present dissertation investigated, by means of data obtained in several research projects, the Continental Shelf between São Paulo and Santa Catarina States, in order to study its morphologic and sedimentary features.

Reflection seismic records allowed to observe the presence of four units and two sub­units in the stratigraphic column of the Santos Basin. Their inner structures reveal the existence of foreset layers and slumps; they also show a wedging towards the slope and thus may characterize an ancient deltaic environment.

Bathymetric profiles, perpendicularly traced to the coast, evidenced the presence of four topographic levels, respectively at 20 to 25m, 32 to 45m, 50m and 60 to 75m. They are probably related to stabilizationperiods of the sea level during the Flandrian transgression.

As to the sedimentation, three facies are predominant: sandy, sandy­siltic­clayey and muddy facies.

The sandy facies predominates in the inner, and partially in the outer shelf; the sandy­siltic­clayey facies is distributed in sporadic areas of the inner and mid­shelf; the clayey facies, texturally made up of clayey silts, occurs over the mid­shelf.

Granulometric analyses, used to an attempt of environmental characterization, evidenced that the Folk & Ward (1957) and Passega & Byranjee (1969) methods are efectively useful for describing and interpreting sedimentary environments where the physical parameters are known.

ASPECTOS SEDIMENTOLÓGICOS E AMBIENTAIS NA REGIÃO ESTUARIAL DA LAGOA DOS PATOS

SEDIMENTOLOGICAL AND ENVIRONMENTAL ASPECTS IN THE ESTUARINE REGION OF THE PATOS LAGOON

Lauro Júlio Calliari (1980)

Adviser: Luiz Roberto Silva Martins

Associated Adviser: Carlos M. Urien

Abstract

The geomorphological evolution, sedimentological characteristics and environmental conditions of the estuarine region of the Patos Lagoon in southern Brazil are discussed in this dissertation.

Environmental (temperature and salinity) and analytical data of 310 bottom samples were collected as part of the Lagoon Project of the BOA (Base Oceanográfica Atlântica), Rio Grande University.

The samples demonstrate that the estuary bottom is covered with sand, silty sand, clayey sand, clayey silt, silty clay and a mixed bottom (sand­silt­clay). Water depth determines the bottom type.

Spacial distribution of heavy minerals was determined qualitatively and quantitatively by gravitative separation and, subsequently, the minerals were identified with a petrographic microscope. The quantitative values obtained in this study showed very low indexes for the analyzed fractions (3 to 4). In most areas values between 0.5 and 1% were found. The qualitative distribution was very significant and allowed to verify the São Gonçalo channel present contribution.

The Ansed system was applied to calculate statistic parameters of different sedimentary patterns. The statistic parameter distribution patterns and relationship coincide and reflect the energy level of each zone.

Based on environmental data alone it was difficult to establish the behavior pattern of the estuary since estuarine dynamics are closely related to the meteorological phenomena. In a general way, it is possible to define seazonal behavior patterns.

The estuarine benthic macrofauna, composed of molluscs, crustaceans and polichaets, presents a low specific diversity but high density, mainly in the mixohaline zone and in the bays where detritus can affect the sediment type, indicating preferential selection for certain bottom types.

CARACTERIZAÇÃO E PLANEJAMENTO AMBIENTAL DO ESTUÁRIO POTENGI

CHARACTERIZATION AND ENVIRONMENTAL PLANNING OF THE POTENGI ESTUARY

Eugênio Marcos Soares Cunha (1982)

Adviser: Luiz Roberto Silva Martins

Associated Adviser: Paulo da Nóbrega Coutinho

Abstract

This dissertation deals with a preliminary diagnosis of the environmental conditions of the Potengi Estuary. Geological, geomorphological and hydrodynamic aspects were emphasized, in order to establish a qualitative model of environmental impacts.

The Potengi Estuary is located in the eastern part of the State of Rio Grande do Norte, being 18 km long and looking like a big tidal inlet, where three intermittent rivers discharge.

Following an appropriate methodology for such complex environments, analytical data of the environmental factors were obtained, such as bathymetry, currents, salinity, temperature, transparence and solid material in suspension, besides the collection of one hundred samples of bottom sediments.

This piece of information points to the sedimentation of suspensionmatter in an estuarine bottom floor made up of sand, silty sand, clayey sand, sandy silt, silty clay and mixed facies. The tidal effects are the main control on the type of sedimentary cover.

The tidal influence, which governs the environmental behaviour, decreases towards the amount of the estuary, where its dimensions are smaller because of the lack of important fluvial contributions. The hydrodynamic pattern established indicates the absense of thermo­saline stratifications, characterizing the estuary as an homogeneous type.

The qualitative analysis of the environmental impact shows that the disordered development of the city of Natal, located on the banks of the Potengi Estuary, is devastating the region.

Finnaly, a better environmental planning is suggested, concerning the natural resources of this region.

MÉTODOS ESTATÍSTICOS NA DETERMINAÇÃO DOS PROCESSOS E AMBIENTES DE SEDIMENTAÇÃO DA PLATAFORMA CONTINENTAL DA REGIÃO SUL­BRASILEIRA

STATISTICAL METHODS FOR THE DETERMINATION OF SEDIMENTARY PROCESSES AND ENVIRONMENTS IN THE CONTINENTAL SHELF OF THE SOUTHERN BRAZILIAN REGION

Sílvia Dias Pereira (1982)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation deals with the employment of statistical techniques to define the best grain size parameters to identify the depositional processes and environments of the continental shelf and slope of Rio Grande do Sul State.

The principal component analysis (PCA) of grain size data of 318 superficial samples of the area pointed out such variables as percentiles (Ø5, Ø16, Ø25, Ø50, Ø75, Ø84, Ø95), percents (gravel, sand, silt, clay), skewness and a derivate variable of the ratio (gravel + sand) / (silt + clay), as the most diagnostic variables for studies in the region.

The use of percentiles, percents and skewness data in cluster analysis, led to the construction of the faciologic map. These analyses indicated three factors which allowed facies identification: a factor of grain position (equivalent to the mean of all values), a second one representing the sorting (equivalent to dispersion), and, the last one, equivalent to skewness. This information allowed the definition of eight sedimentary facies: 1) Sand Facies - deposition of terrigenous sand in beach and inner shelf environment.

2) Patos Facies - present deposition of fluvial mud in marine coastal environment.

3) Shelf Mud Facies - past deposition of fluvial mud in quiet water marine environment.

4) Platina Facies - past deposition of fluvial mud, in an environment analogous to the previous one, but with the La Plata River influence.

5) Transitional Facies - remobilization and deposition of mud, causing a mixture with the sand.

6) Inner Biodetritic Facies - biodetritic gravel concentration by erosion in the deepest Pleistocene beds which contain it.

7) External Biodetritic Facies - past concentration of biodetritus in marine environment of the inner shelf.

8) Slope Mud Facies - past deposition of fluvial mud in marine slope environment.

The last stage was the trend surface analysis of the derivate variable of the ratio (gravel + sand) / (silt + clay), to obtain information about depositional environments and associated energy levels. The 3rd order trend surface was considered the best one to define the regional component of these data, confirming the already existing sedimentary model of the area. The local component (deviations) of this same trend showed, in some places, lower energy levels than those expected for them.

ASPECTOS SEDIMENTOLÓGICOS DO CANAL DE SÃO GONÇALO

SEDIMENTOLOGICAL ASPECTS OF THE SÃO GONÇALO CHANNEL

Heleny Vieira (1982)

Adviser: Jorge Alberto Villwock

Abstract

The study of bottom sediments of São Gonçalo channel, a natural connection between Patos and Mirim Lagoons, shows that they have been deposited in two distinct zones. One inside, in fluvial environment conditions and along the channel, and another one, at its end, under the influence of lagoonal bodies. Sands, clayey­silts, sandy­silts, silty­sands, silty­clays, sand­silty­clays, silts, and clayey­sands, are the main textural facies. The distribution of these facies shows some areas that have been receiving sediments (Piratini river and Pelotas creek) and others that have been eroded, furnishing sediments to the estuarine complex of Patos Lagoon. Coarse facies predominate at the deeperparts of the channel and fine facies occur at the shallow ones.

Heavy and clay mineral assemblages show that the main source areas are the Cenozoic formations, which have been reworked by the channel currents, and the rocks of the crystaline basement, which are drained and eroded by some of its tributaries.

Geomorphological analysis of this area accounts for the existence of an old lagoonal bottom which is now a lone­land, exposed after the last Holocene Transgression, where the channel is meandering. It is possible to see there point bars, natural levees, clevasse­splay, flood­basin, flood­plain and channel fill deposits.

ASPECTOS SEDIMENTARES DA PLATAFORMA CONTINENTAL DE SANTA CATARINA

SEDIMENTARY ASPECTS OF THE SANTA CATARINA CONTINENTAL SHELF

João Carlos Rocha Gré (1983)

Adviser: Luiz Roberto Silva Martins

Abstract

The sedimentary nature and distribution of the Santa Catarina continental shelf is presented.

The sediments of the continental shelf are present in the area covering the Pelotas and Santos basins.

The granulometric, morphoscopic and sandy components, characteristic of the samples taken during Geomar XIV Expedition, were studied.

Three populations were observed on the shelf: siliceous sands, biogenic sands and terrigenous muds.

Siliceous sands occur on the internal shelf. They are products of reworking of the underlying Pleistocene deposits in coastal environment.

Biogenic sediments are characteristic of the middle shelf but, presently, are concentrated on theouter shelf. They seem to be deposited during regressive environmental conditions.

Terrigenous muds are dominant in the middle shelf. They cover partially the siliceous and bioclastic sands in the internal and external shelf. Their deposition is related to a transgressive environmental condition.

Geologic history of the southern Brazilian continental shelf is mainly based on the sea level variations during the last glacial cycle and modern hydrodinamic adjustment.

Some economic aspects have been reported. Deposits of quartzitic sand and carbonatic sand are potentially valuable, and further studies may perhaps delineate heavy mineral deposits.

CONTRIBUIÇÃO AO ESTUDO TECNOLÓGICO DOS SEDIMENTOS ARENOSOS RECENTES DO ESTADO DO RIO GRANDE DO SUL - BRASIL

A CONTRIBUTION TO THE TECHNOLOGICAL STUDY OF THE RECENT SANDY SEDIMENTS OF THE RIO GRANDE DO SUL STATE - BRAZIL

Alberto Antônio Müller (1984)

Adviser: Luiz Roberto Silva Martins

Abstract

An universal concern about the study of the non­metallic substances has been considerably emphasized recently. It is worth noticing the significance of such a study concerning the survey of the technological properties of a certain mineral of a given region, based on laboratory and field data which aim at a qualitative knowledge of the basic material available to production.

References review showed that sand is a material which has multiple applicability, even susceptible of usage by many industries, such as the glass industry. It is important to notice that, considering its own applicability, sand, concerning its inner and final constitution, is a material that is offered by nature ready to use.

In this dissertation we present a detailed study of a number of geographical areas with recent sandy sediments, inlet in the Coastal Province and in the Peripheral Depression of Rio Grande do Sul, in accordance with occurrences of the fluvial and coastal Quaternary in this State, which made it possible to clear up some chemical and sedimentary relations, relevant to the prospect of sand for the glass industry.

Based on this study, some comparisons of technological character between occurrences of sand studied in Rio Grande do Sul are made, in order to show parameters of usage.

Concerning the technological aspect, it is demonstrated in this study that sand has to fulfill two main requirements: granulometry and appropriate chemical and mineralogical composition, based on the requirements of the companies that make use of such raw material and on the insufficient data that have been found in the specialized bibliography.

On the bases of the geological and technological aspects concerning age, origin and physical­chemical properties of certain Quaternary sandy systems, we obtained several results about the sand potential of Rio Grande do Sul, regarding quality and usage control.

SEDIMENTOLOGIA DA LAGOA DAS CUSTÓDIAS: CONTRIBUIÇÃO AO ESTUDO DE LAGOS COSTEIROS

SEDIMENTOLOGY OF THE CUSTÓDIAS LAGOON: A CONTRIBUTION TO THE STUDY OF COASTAL LAKES

Neida Maria dos Santos (1986)

Adviser: Luiz Roberto Silva Martins

Abstract

The Custodias Lake pertains to the coastal lakes that represent one of the most typical sedimentary environment from the Coastal Dominion of Rio Grande do Sul.

With the purpose of studying the sedimentary model of Custodias Lakein detail, the textural aspects of the twenty­one superficial samples were analyzed.

The sedimentology and the sedimentation rate characterize the Custodias Lake as a coastal lake in accelerate depositional process.

ASPECTOS DA DINÂMICA SEDIMENTAR NO RIO DE LA PLATA EXTERIOR E PLATAFORMA INTERNA ADJACENTE

ASPECTS OF THE SEDIMENTARY DYNAMICS IN THE OUTER RIO DE LA PLATA AND ADJACENT INNER SHELF

Ricardo Norberto Ayup Zouain (1986)

Adviser: Luiz Roberto Silva Martins

Associated Adviser: Jorge Alberto Villwock

Abstract

The Rio de La Plata is an important regional element in the South American platform. Its hydrodynamic conditions and sedimentary aspects are important for characterizing the conditions of sedimentary exchanges with the adjacent continental shelf. By developong a method adequate for assessing the complex continental shelf estuary, analytical data of ambiental factors, geological and morphological information, samples of superficial bottom sediment and suspended sediment were obtained. Different elements interacting in the environmental dynamics and different estuarine circulation, patterns conditioning the behaviour of suspended sediments as well as sedimentary transport and deposition in the continental shelf were studied. The information thus obtained will permit the designing of a sedimentary model drawn from the suspended load that modifies the internal sedimentary conditions in the Rio de la Plata and adjacent continental platform.

The estuarine tidal cycle appears as an important factor for the displacement of "turbidity bodies" in the estuary. Estuarine circulation patterns favour the sedimentary deposition in the inner and southern parts of the Rio de la Plata Estuary while the northern part shows complex mechanisms for sediment deposition, resuspention and suspended transport. The suspended transport observed in superficial waters (pluma) and/or in bottom waters ("turbidity current") reaches the continental shelf and distributes the transported sediment.

Present sedimentary contribution of the Rio de la Plata in the continental shelf ranges from 19.9 to 70.4×106 tonne/year with an average of 59.13×106 tonne/year. The sedimentary average deposited in the Rio de la Plata originating from this basin is about 70×106 tonne/year; this brings about changes within the morphological characteristics and sedimentary facies of the system. Transport conditions created by "turbidity current" suggest present sedimentary contribution in the Uruguayan and South­Brazilian continental slope to be probable.

EVOLUÇÃO PALEOGEOGRÁFICA DA BACIA DO RIO GRAVATAÍ

PALEOGEOGRAPHIC EVOLUTION OF THE GRAVATAÍ RIVER BASIN

Luci Maria Arienti (1986)

Adviser: Jorge Alberto Villwock

Abstract

Geologic­geomorphologic, sedimentalogic and evolutive analyses of an area located in the Northeast part of the Coastal Province of Rio Grande do Sul are presented. This area consists of extensive deposits of alluvial fans, a barrier system and two lagoonal terraces behind the barrier complex as well as fluvial and swamp deposits.

The alluvial fans represent piedmont deposits which were formed at the Tertiary during lowstand periods of the sea level, with torrential rains, and in dry climates, thus constituting coarse and poorly selected sediments of the paraconglomerate type.

The barrier system is composed of an elongated sandy body which is aligned towards the Northeast. It represents the oldest barrier of the Coastal Province of Rio Grande do Sul which was settled in the first transgression­regression of the Pleistocene. This barrier consists of two regions with distinct characteristics. They are interpreted in this study as old junction inlets of the lagoon with the sea at the time, and which later on during the geologic evolution of the area were filled up.

In addition, there are lagoonal terraces constituted by clay and sandy materials which were formed during the sucessive Quaternary marine changes. The fluvial deposits can be subcurrent, presenting themselves as abandoned terraces in more topographically elevated levels, as well as current ones normally converging to the Gravataí River Basin.

The Gravataí River, because of its hydrologic system and the sedimentologic and morphologic characteristics of its alluvial plains, acts as a meandring river which produces the drainage of the water of the basin. It was probably formed when the Lombas Barrier was closed down, thus an increase of the water level of the lagoon behind this barrier was produced, causing a narrow and deep channel to be excavated in the gondwanic terrains.

The swamp deposits are present in the Pachecos­Chico Lomã Swamp and they may have peat accumulations, which are economically useful.

Eighteen chemical analyses of clay­minerals were made, and it was clearly observed that kaolinite was the dominant material.

A model of paleogeographic evolution is presented, representing nine evolutive stages, which were responsible for the present morphologic configuration of the Gravataí River Basin, related to the glacio­eustatic changes of the sea level during the Pliocene and Quaternary.

GEOLOGIA DAS FOLHAS DE TORRES, TRÊS CACHOEIRAS, ARROIO TEIXEIRA E MAQUINÉ, NORDESTE DO RIO GRANDE DO SUL

GEOLOGY OF THE TORRES, TRÊS CACHOEIRAS, ARROIO TEIXEIRA AND MAQUINÉ QUADRANGLES, NORTHEASTERN RIO GRANDE DO SUL

Norberto Olmiro Horn Filho (1987)

Adviser: Jorge Alberto Villwock

Abstract

The results of the geomorpho- logical­geological mapping executed in the northeast region in Rio Grande do Sul Coastal Plain, between the 29°15' and 29°45' south latitudes and the 49°30' and 50°15' west longitudes, including the planialtimetric charts of the Army's Geographical Service of Torres, Três Cachoeiras, Arroio Teixeira and Maquiné's Quadrangles, are presented.

The main outcroping surface units on the mapped area consist of shallow marine, aeolian, lagoonal, deltaic, fluvial and alluvial fan sediments, that overlie the Gondwanic formations of Paraná Basin, represented by aeolian sandstones of the Botucatu Formation and by basaltic rocks of the Serra Geral Formation.

These sedimentary facies identify depositional systems of the lagoon/barrier type, characterizing two sandy barriers, III and IV, associated, respectively, to Upper Pleistocene and Holocene transgressive­regressive events, and inserted in the Multiple Complex Barrier proposed by Villwock (1972).

CONTRIBUIÇÃO À EVOLUÇÃO PALEOGEOGRÁFICA QUATERNÁRIA DA PLATAFORMA CONTINENTAL DO RIO GRANDE DO SUL

A CONTRIBUTION TO THE QUATERNARY PALEOGEOGRAPHICAL EVOLUTION OF THE RIO GRANDE DO SUL CONTINENTAL SHELF

Sérgio Rebello Dillenburg (1988)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation deals with the study of the morphologic features and the sediments of the surface of the continental shelf­edge zone as well as its shallow subsurface depositional features, with the purpose of identifying and detailing the depositional model established in this zone during the last Wiscosinan lowstand of sea level.

The morphologic features, the sediments, and the sedimentary subsurface features observed permitted to divide the study area into three sectors: the southern, the northern and the central sectors.

Evidence obtained from bathymetric, high resolution reflection seismic, and sedimentologic data (textural composition, mineralogic maturity, and sediments morphoscopic characteristics) pointed to the occurrence of a high rate of sedimentation associated with a deltaic system in the southern sector of the study area during the last lowstand of the sea level.

The deltaic system established in this sector was related with the Rio de la Plata fluvial system, which influenced the shelf­edge sedimentation, approximately until the Rio Grande Cone during the last sea level lowstand. In the northern sector, it was observed a major influence of the Uruguai and Rio Grande do Sul highlands fluvial drainages, mainly marked by the presence of sandy sediments of higher values of mineralogic maturity than those observed in the southern sector.

The central sector shows intermediary sedimentologic characteristics in reference to the southern and northern sectors. However, it was verified a major influence of the Rio de la Plata fluvial system in the sedimentation of the sector.

The identification of a deltaic depositional system permitted to conclude that during the sea level lowstand, other sedimentary environments of the transitional type were developed in the shelf­edge zone.

The presence of pyroclastic materials (Volcanic glass) was observed in the surface sediments that cover the outer continental shelf, mainly in the southern and central sectors.

The present study contributes to a better knowledge of the evolutional aspects of the Rio Grande do Sul continental shelf in the Quaternary.

MAPEAMENTO GEOLÓGICO E GEOMORFOLÓGICO DAS FOLHAS DE SÃO LOURENÇO DO SUL E BOQUEIRÃO

GEOLOGIC AND GEOMORPHOLOGIC MAPPING OF THE SÃO LOURENÇO DO SUL AND BOQUEIRÃO QUADRANGLES

Ronaldo Antônio Gonçalves (1989)

Adviser: Jorge Alberto Villwock

Abstract

This dissertation presents the results of the geologic and geomorphologic mapping in scale 1:50.000 of the west side of the Patos Lagoon, near São Lourenço do Sul and Boqueirão cities in Rio Grande do Sul State.

Through airphotos and satellite photos interpretation and field work made it possible to define two geomorphologic dominions namely, the highlands and the lowlands. The first one includes the lands located at an elevation higher than 25 meters considered in the present work as the topographical limit between the two dominions; the second one extends from that limit to the side of the Patos Lagoon. In the lowlands dominion a number of morphological features were characterized and classified as: aluvial terrace, located between 22 to 6 meter elevations approximately; abrasion terrace at the elevations between 5 to 3 meters limited by two cliffs, one internal and located at the west limit and the other external and located at the Patos Lagoon limit; fluvial terraces located alongside the present drainage and a system of beach­lagoonal ridges located parallel to the lagunar coast.

It was carried out a faciological analysis of the sedimentary cover found in the area where the sedimentary facies of elluvium, colluvium, alluvial fans, recent alluvial fluvial and the facies of beach­lagoonal ridges were defined. The elluvial and colluvial facies and part of the facies of the alluvial fans were grouped for defining a depositional system of alluvial fans which were found spacially associated.

Through the granulometric, mineralogical and morphoscopic analysis it could be verified that the textural and mineralogical immaturity is a sedimentary attribute found in all the sedimentary facies mapped. In the morphoscopic aspect predominate the 0.3 - sub­angular indexes to round out and 0.5 - average to the sphericity. Mineralogically the quartz and the feldspar are the predominant minerals characterizing an arcosean composition to these sediments.

For the depositional system of the alluvial fans it was adapted an evolutional model that aims to illustrate the spacial distribution of the sedimentary facids so as to offer an idea of the sedimentary processes responsible for this system. Nevertheless, for a complete definition of these depositional processes, it is necessary to obtain more data than the already obtained ones in the studied area, since the present work is restricted to two cartographic charts of the Serviço Geográfico do Exército, namely, São Lourenço do Sul and Boqueirão.

OS EFEITOS DO TRANSPORTE SEDIMENTAR NA DISTRIBUIÇÃO DOS TAMANHOS DE GRÃO E MORFODINÂMICA DA LAGOA DOS PATOS

EFFECTS OF THE SEDIMENTARY TRANSPORTATION ON THE GRAIN SIZES AND MORPHODYNAMICS OF THE PATOS LAGOON

Elírio Ernestino Toldo Júnior (1989)

Adviser: Luiz Roberto Silva Martins

Abstract

The submerged relief of the lagoon body was delimitated, based on morphometric and sedimentological data, in two distinct regions: the internal lagoon margin and the lagoon floor.

The former includes the whole area between the coastal line and the 5 meter isobath, whereas the latter corresponds to a flat, slightly sloped surface, which develops beyond the 5 meter isobath.

The internal margin, both in the northern sector and in the eastern and western sectors, develops on Cenozoic coastal deposits. These deposits, besides conditioning the lagoon body laterally, are important internal sources of sediments.

The external sediment source is more significant than the internal one; it occurs in a greater volume in the northern part of the lagoon because of the tributaries of the Guaíba Complex. The solid load of the external sediment source is directly related to the building­up of the lagoon floor.

The study of the effects of sediment transport on the grain size distribution on the lagoon floor allowed the development of a model, without equations, which enabled the evaluation of preferential directions for sediment transport, and consequently the dominant circulation patterns.

The basis of this model are the variations in sediment size concentrations in Ø units, and their distribution throughout the lagoon floor.

The analysis of the genesis of the lagoon floor body, utilizing morphological and sedimentological information, suggests the existence of ancient coastal processes, responsible for the construction of ancient beach lines and sand hooked spits, which are now submerged.

Moreover, analysing the present lagoon morphodynamics, it was possible to report the presence of three important coastal processes:

- the present hydrodynamic equilibrium of the submerged sand hooked spits, here called banks;

- the present mechanism for the growth of emerged sand hooked spits, here called spits;

- the erosion process along the southern portion of the inner eastern margin.

We believe that the three previous coastal processes responsible for the lagoon morphodynamics are the products of a recent transgressive event, related to the effects of the Holocene sea level changes, and of the large amount of water contributions by the southeastern drainage basin of the State of Rio Grande do Sul.

Complementary data concerning the deposition rate on the lagoon floor, based on method U238, added to the erosion and accretion characteristics along the internal margins, allowed the setting up of a model forecasting the fate of Patos lagoon.

MODELO DEPOSICIONAL HOLOCÊNICO DA PLATAFORMA EXTERNA, ZONA DE QUEBRA E TALUDE SUPERIOR DA MARGEM CONTINENTAL DO RIO GRANDE DO SUL ­ TRECHO RIO GRANDE/TORRES

HOLOCENE DEPOSITIONAL MODEL FOR THE OUTER SHELF, SHELF BREAK AND UPPER SLOPE OF THE RIO GRANDE DO SUL CONTINENTAL MARGIN, FROM RIO GRANDE TO TORRES

Josemar Santos Pereira Filho (1988)

Adviser: Luiz Roberto Silva Martins

Abstract

The area in point lies on a reasonably steady continental border of which stratigraphical evolution and structuring result from the separation of South American and African plates. The paleogeographic evolution of the most modern areas covering the external shelf, cliff zone and upper slope is consequence of glacio­eustatic changes which took place from the Upper Wisconsinian known as Holocene Transgression. The horizontal distribution of the textural characteristics of size of the particles shows the mainly reliquian nature of these sediments, where one can note a concentration of coarses or biotica in the external shelf and cliff zone, reflecting a Pre­Holocene level of stabilization. Of the same reliquian nature, the thin material of the middle shelf is probably covering ancient channels and valleys related, regarding the meridional area, to the ancient drainage system of Rio da Prata; the fines of slope, also relics, result from an intense gathering of material which comes from Rio da Prata and from the drainage of the highlands of Rio Grande do Sul flowing into the neighborhood of this area. The action of prograding depositing mechanisms with hemi­pelagic characteristics, as well as typical sequences produced by gravitational flows of sediments are clearly recognized from the evidences collected about the cliff zone and upper slope. In some instances, however, it's possible to identify typically reliquian sequences in the external shelf, which result from littoral features as bars, sandbars, etc. The coarse material, of mainly quartzons nature, aggregated to a round formation with a polished saccharoidal superficial aspect, mostly found in the external shelf and cliff zone, reflects on average to high level of reworking taken place in a fluid milieu. This fact confirms once again an energetically significant depositing environment in a Pre­Holocene abated sea level.

CONTRIBUIÇÃO À GEOLOGIA DA REGIÃO DE BARRA DO RIBEIRO

CONTRIBUTION TO THE GEOLOGY OF THE BARRA DO RIBEIRO REGION

Flávio Antônio Bachi (1989)

Adviser: Jorge Alberto Villwock

Abstract

A geologic­geomorphologic­sedi-mentologic study of depositional environments, their products and relations with the determinant events of their current morphology was developed in an area located in the western margin of Patos Lagoon and mapped on the scale of 1:50,000.

These environments are represented by deposits of alluvial fans, barrier, lagoonal and fluvial facies. They comprise geomorpho-logically four basic units: Basement, Barrier I, Araçá­Guaíba Lagoon System, and Holocenic Lagoon Margin.

Their paleogeographic evolution is directly related to the changes of the sea level in the Quaternary, represented in the area by nine evolutive stages.

USO DE IMAGENS ORBITAIS "TM" - LANDSAT 5 NA CARACTERIZAÇÃO DE AMBIENTES PALUDAIS NA PLANÍCIE COSTEIRA DO RIO GRANDE DO SUL

THE USE OF "TM" ORBITAL IMAGES - LANDSAT 5 FOR THE CHARACTERIZATION OF PALUDAL ENVIRONMENTS OF THE RIO GRANDE DO SUL COASTAL PLAIN

Dejanira Saldanha Frantz (1989)

Adviser: Jorge Alberto Villwock

Associated Adviser: Clóvis Carlos Carraro

Abstract

Paludal deposits situated on the Coastal Plain of Rio Grande do Sul were characterized by TM orbital images from satellite Landsat 5, registered during a very dry summer (January/1986). These deposits are associated with an environment of a paleolagoon isolated from the sea by a Pleistocenic barrier named Barreira das Lombas. Areas inserted in this paleolagoon by continuous input of material developed into paludal environment in which different vegetable associations found good conditions for their development. The preservation of organic matter was due to high moisture, originating the peat deposits that were found there.

The multispectral images used in this dissertation, because of their best spectral, spatial, and radiometric characteristics, permitted the delimitation of these environments, determined by geology, geomorphology, soils and vegetation. Considering the great amount of data transmitted by these images and with the purpose of image enhancement, were applied in the GE­Image­100 the following algoritms: contrast strech, band ratio, principal components, and colored compositions. A pre­process-ing including radiometric and atmospheric corrections was done.

The best enhancement process used was the colored compositions formed by bands with contrast strech. In these compositions the best results were obtained by the utilization of a channel in the visible region (2 or 3), a channel in the near infrared (4), and the third in the medium infrared region (5 or 7). In this analysis there is a high relationship between the natural compartments and the units limited in the images. Besides, a zonation in the vegetation can be seen in the peat deposits because of the diversified structure in them. This can identify the best region of organic matter concentration.

All channels in the reflective region of the spectral eletromagnetic were used in the band ratio in which the 4/3 image indicated the biomass, the 5/2 the differences in the quality of vegetation, and 7/1 the differences in the content of moisture. The three ratio images originated colored compositions and were used as complementary analyses. The image reached by the process of principal components didn't add new data to the initial interpretation because, through their statistical parameters, they showed to be similar to the original images.

CONTRIBUIÇÃO AO ESTUDO DA SEDIMENTAÇÃO GLACIO­MARINHA DA BAÍA DO ALMIRANTADO, ILHA REI JORGE, ANTÁRTICA

CONTRIBUTION TO THE STUDY OF THE GLACIMARINE SEDIMENTATION IN ADMIRALTY BAY, KING GEORGE ISLAND, ANTARCTICA

Nelson Luiz Sambaqui Gruber (1989)

Adviser: Luiz Roberto Silva Martins

Associated Adviser: Iran Carlos Stalliviere Correa

Abstract

With the purpose to contribute for a better knowledge of the glacial and glacimarine sedimentation of the Admiralty Bay region (62°10'S., 58°25'W.), situated at the King George Island, South Shetland Islands Archipelago, 88 superficial geologic samples and 23 water samples were analyzed. Concerning the Brazilian Antarctic Program - PROANTAR, this study was developed during 3th, 4th, 5th and 6th Antarctic Expeditions (1985­1988).

Studies developed on the sedimentation patterns and bottom morphology of the Admiralty Bay show a strong tectonic control over the subaerial and submarice phisiography, whose generation process is related to the island­arc evolution history.

Submitted to two main trend fault systems (ESE­WNW and NNE­SSW), the geology of King George Island exhibits several faulted blocks, like "grabens" and "horsts"which, associated with lithological differences and strong glacial excavation, produced a very complex and compartmented physiography.

In face of such a complex of features presented, we classified the studied area as "glaciers­dominated fiord", being suggested a morpho­sedimentological compartmentation into four distinct units: Martel Inlet, Mackellar Inlet, Ezcurre Inlet and Bay Channel.

By means of granulometric analysis of the bay bottom sediment, five textural facies were identified: Mud with sand and gravel; Sandy mud; Muddy sand; Mud with gravel and Muddy.

According to environmental characteristics observed, we adopted a glaci­estuarine model to explain these glaci­marine deposits patterns and the circulation and the behavior of water masses into the Fiord System.

GEOLOGIA E GEOMORFOLOGIA DAS FOLHAS DE MORRETES, SÃO LEOPOLDO, SÃO JERÔNIMO, GUAÍBA E ARROIO DOS RATOS ­ RS

GEOLOGY AND GEOMORPHOLOGY OF THE MORRETES, SÃO LEOPOLDO, SÃO JERÔNIMO, GUAÍBA AND ARROIO DOS RATOS QUADRANGLES - RS

Heinrich Theodor Frank (1989)

Adviser: Jorge Alberto Villwock

Abstract

The northern and western areas of Porto Alegre city, Rio Grande do Sul State, Brazil, show on the north of the Jacui and Gravataí rivers gondwanic sedimentary rocks and on the south of these rivers granitic rocks of the Sul­Riograndense shield. Between the two units occur Cenozoic sediments of lagoonal and dominantly fluvial origin, distributed into 2 fluvial terraces and 2 lagoonal terraces. Fluvial Holocene deposits also occur. The most recent terraces have many features preserved related to their lagoonal or fluvial origin. The origin of these features could be partially deduced from the description and characterization of the present behavior of the rivers in the area.

Nine paleogeographic stages have been recognized, beginning with a Pliocene regression responsible for the origin of the first generation of alluvial fans, passing through 3 cycles of transgression­regression of Pleistocene age and ending by a Holocene cycle, whose features are the most conspicuous.

We suggest the mapping of the gondwanic sediments using the concept of "facies" to eliminate the continuous contradictions originated by the filling typology of the Paraná basin. Furthermore, we recognize the necessity to improve the approach and knowledge of the so­called "slope­deposits", where sediments accumulated by different processes are grouped in only one stratigraphic unit.

The mineral resources of the area are varied and their exploration could be bettered, what must be accompanied by rigorous environmental preservation criteria considering the many existing negative aspects which have been described in the chapter referring to the environmental situation of the area.

GEOLOGIA DA REGIÃO DE TAPES - RS

GEOLOGY OF THE TAPES REGION - RS

Luiz Fernando Ev (1990)

Adviser: Jorge Alberto Villwock

Abstract

The geologic structure of the eastern part of Rio Grande do Sul comprises two major units: the basement and the Pelotas basin. The first one is represented by the Dom Feliciano belt (gneisses, migmatites, molasse sequences) of Upper Proterozoic/Early Paleozoic, and by Paleozoic and Mesozoic volcanic and sedimentary sequences of the Paraná Basin.

The Pelotas basin is a passive margin basin with a dominant clastic sequence of 5,000m thick. Its development has occurred during the Upper Jurassic and is related to the opening of the South Atlantic Ocean.

The emerged part of the Pelotas basin is the Rio Grande do Sul coastal plain which can be subdivided into inner and outer plains. The inner plain comprises clastic deposits and massive accumulations which delineate the primitive Rio Grande do Sul coast­line. The outer coastal plain is composed of marine deposits moulded from transgressive­regress-ive events of the Middle Pleistocene­ ­Holocene.

The primary aim of this dissertation is the geological study of Tapes area, part of the inner coastal plain of Rio Grande do Sul.

Sedimentary and geomorphological aspects of the area have been analyzed in detail and depositional systems have been established and individualized.

The evolution of the area has shown to be closely related to eustatic fluctuations which affected the southern portion of Brazilian coast­line. The Tertiary tectono­eustatic and Quaternary glacio­eustatic oscillations are the most important of such fluctuations.

The resulting morphoclimatic zoning has developed a polycyclic landscape by means of pedogens and lateral and vertical dissection processes.

The proposed evolutionary model comprehends ten stages. The first ones are correlated to the first sedimentary records at 1­GA­1­RS and 1­GA­2­RS wells (30km to the south of the studied area), Upper Oligocene/Miocene. Miocene marine sediments whith fossils cover this sequence.

Interglacial periods have risen the sea level at least three times during the Pleistocene. The related deposits are sandy barriers and lagoonal terraces.

Between the high sea level phases, glacial periods have inserted the regressive condictions, thus establishing the advance of continental sedimentation by means of alluvial fan systems.

The progressive separation of the Patos­Mirim lagoonal system begins as a result of the construction of outer sandy barriers. The Flandrian transgression completes that process by means of a fourth barrier at the outer plain during the Holocene.

This transgression as well as the preceding ones have been characterized by several pulses of variable duration and intensity, with a maximum at 5,100­5,500 years B.P. A lagoonal terrace is the sedimentary record of the transgression. At the top of that terrace, features indicate three submerging periods.

The internal dynamics of the Patos lagoon has promoted the adjustment of the coast line after the last transgressive event, and the region acquired its now­existing shape.

A EXPLORAÇÃO DE AREIA NA REGIÃO DE TRAMANDAÍ E O IMPACTO AMBIENTAL

THE SAND EXPLOITATION IN TRAMANDAÍ AND THE ENVIRONMENTAL IMPACT

Luiz Nildo Ferreira Dutra (1990)

Adviser: Jorge Alberto Villwock

Abstract

The coastal region of Rio Grande do Sul has been the target of countless environmental degradation denunciations. One of its major areas is in the Tramandaí region, mainly because it is a touristic attraction pole.

Among the activities considered harmful to the environment, consequently the target of those denunciations, is mining. Therefore, this research aims to characterize different aspects of the various types of mining that exist in this coastal region of the State, as well as the principal environmental problems caused by them.

The environmental problems in this region, however, are not caused exclusively by mining. For this reason, an analysis has also been made of the environmental impacts caused by other forms of soil occupation. This analysis, from the geological point of view, applies to the urban as well as the rural areas.

The environmental analysis presented here has been prepared in an ample manner, without a specific order as to the importance of the various impacts.

Since many of the environmental problems could have been avoided simply by obeying the existing legislation, several considerations have been applied to the legal aspects, relating them to the various activities developed, particularly mining.

In this manner, the area chosen for the analysis of the problems presented is that delimited by the topographical charts of Osório, Tramandaí, Rancho Velho and Cidreira. These charts, published by the Board of Directors of the Geographical Service of the Military State Department in the scale of 1:50,000, are situated between the parallels ­29°45'00" and ­30°15'00" and the meridians 50°00'00" and 50°30'00".

ESTUDO DOS TERRAÇOS MARINHOS DA PENÍNSULA FILDES, ILHA REI GEORGE, PENÍNSULA STANSBURY, ILHA NELSON E ILHA ARDLEY, SHETLAND DO SUL, ANTÁRTICA

STUDY OF THE MARINE TERRACES IN THE FILDES PENINSULA, KING GEORGE ISLAND, STANSBURY PENINSULA AND NELSON AND ARDLEY ISLANDS, SOUTH SHETLAND, ANTARCTICA

Marco Antônio Fontoura Hansen (1990)

Adviser: Luiz Roberto Silva Martins

Abstract

Studies carried out in the coastal areas of the Fildes and Stansbury peninsulas (King George Island and Nelson Islands) and Ardley Island, South Shetland Islands, Antarctica, made it possible to know more accurately the marine terraces through planialtimetrical profiles. The establishment of their Holocene and Pleistocene ages was the result of careful analyses and comparative research. A special approach was given to the profiles of the "Ship" (A­A') and Wal (F­F') bays, in the Fildes Peninsula, and to the Rip (G­G') bay, in the Stansbury Peninsula.

The production of regional and local geological maps, specially of the profiled bays, and stratigraphic successions and chronostratigraphic tables were also part of the study.

The description included the morphologic aspects of the marine, transitional and continental areas, suggesting a geomorphological compartmentalization for the emerged portion, attaching special attention to the coastal area. Among the most prominent features of the area we can mention the marine terraces, lagoons, lakes, bays, spits of land, dunes and deltaic micro­fans. We found a medium integrated emersion curve asosciated with the phases of the glaciers in the last 9,000 years BP, making it possible to discover the approximate ages of the raised terraces, lakes and drainages.

Out of the eight profiles which were carried out, we selected the three most representative ones in order to analyze the thirty­three samples of sediment collected on berm crests and runnels: the proprieties of sedimentary character, including granulometric, statistical, morphoscopic parameters, and classifications. The described Quaternary deposits are characterized by glacial, colluvial, of slopes, glaciofluvial, glaciolacustrine, of marine terraces, lagoonal, aeolian, glaciomarine, and marine sediments.

The paleogeographic analysis resulted in the establishment of two evolutional stages from the Upper Pleistocene to the Recent, and paleogeographic maps of the Upper Pleistocene and Upper­Middle Holocene were also drawn. The proposition of these stages is related to the main factors responsible for the coastal configuration, represented specially by the glacio­isostasy, the glacio­eustasy and neotectonics, linked to the climate flutuations that have occurred.

MECANISMOS EROSIVOS E DEPOSICIONAIS EM AMBIENTE COSTEIRO E PRAIAL MARINHO NAS BAÍAS WAL, ESPERANÇA E LOBOS MARINHOS - PENÍNSULA FILDES - ILHA REI GEORGE - SHETLAND DO SUL - ANTÁRTICA

EROSIONAL AND DEPOSITIONAL MECHANISMS ON COASTAL MARINE ENVIRONMENTS ALONG WAL, ESPERANÇA AND LOBOS MARINHOS BAYS, FILDES PENINSULA, KING GEORGE ISLAND, SOUTH SHETLAND, ANTARTIC

Fábio Luiz Troian (1990)

Adviser: Luiz Roberto Silva Martins

Abstract

In this study are presented and discussed climatic, geotectonic geologic and structural characters, and also glacial and fluvio glacial events of the N­NE Region, Peninsula Fildes, Dreak Ocean.

The morphostructure is represented by the High Lands of Central­Nord, Ocidental Platform, and the Coastal Region.

The morphogenetic features and the textural characteristics are controlled by many factors associated with marine and wave dinamics.

Geological mapping alowed to identify many depositional features like eolian dunes, glacio fluvial drainage, eskers, kames, and a complex cryopedologic system, with the development of polygonal soils, which cover the geomorphological sectors, plained off by marine abrasion and glacial action.

CARACTERIZAÇÃO MORFO­SEDIMENTOLÓGICA DO MICRO LEQUE DELTAICO DA BAÍA ESPERANÇA, PENÍNSULA FILDES, ILHA REI JORGE, SHETLAND DO SUL, ANTÁRTICA

MORPHO­SEDIMENTOLOGICAL CHARACTERIZATION OF THE MICRO FAN DELTA OF HOPE BAY, FILDES PENINSULA, KING GEORGE ISLAND, SOUTH SHETLAND, ANTARCTIC

Maria Victoria Soto Bäuerle (1991)

Adviser: Jorge Alberto Villwock

Abstract

During field work developed under the auspices of the Brazilian Antarctic Program, researchers of the CECO/UFRGS (Center for Studies in Marine and Coastal Geology of Federal University of Rio Grande do Sul) observed the occurrence of a micro fan delta in the Fildes Peninsula.

Situated at the nearshore of Hope Bay, the micro fan delta was studied from a morpho­sedimentary point of view during the summers of 1989 and 1990. It was found that its features are associated with a braided fluvial system developed during ebb tidal time.

The bars and channels of the braided system constitute lobes, which reaching their maximum deposition, start a migration of the fluvialnet to a more favorable slope, where new lobes are built. The depositional processes and the migration are cyclical, occurring at each ebb tidal time. Since they are highly dynamical features, a morpho­lithological classification is proposed, aiming at a systematization of the changes and evolutive stages observed at the micro fan delta.

Geomorphologically, the micro fan delta of Hope Bay presents the evolutive dynamics of a fan delta of periglacial conditions, though exhibiting a pattern of differentiated space­temporal scale which, analyzed from the point of view of the changes rate, is similar to an outwash plain and, in reference to its sedimentologic aspects, to a nearshore environment.

RELAÇÕES MORFO­SEDIMENTOLÓGICAS ENTRE O ASSOALHO OCEÂNICO DA BAÍA MAXWELL E PRAIAS ADJACENTES, ILHA REI JORGE E ILHA NELSON, ANTÁRTICA

MORPHO­SEDIMENTOLOGICAL RELATIONSHIPS BETWEEN THE OCEANIC FLOOR OF MAXWELL BAY AND ADJACENT BEACHES, KING GEORGE AND NELSON ISLANDS, ANTARCTIC

Carmen Paz Castro Correa (1991)

Adviser: Luiz Roberto Silva Martins

Abstract

This dissertation deals with the morpho­sedimentological relationships between the coast and the ocean bottom from Maxwell Bay and the adjacent beaches, South Shetland Island, Antarctica.

The climatic situation of the area was determinant in the development of the morpho­sedimentological features. This is a sub­polar zone with wet­based glaciers, associated with an important "glaciofluvial" component.

Thus, the prevailing transport and depositional mechanism in Maxwell Bay is by suspension, associated with the "glaciofluvial" component, and with the turbulence of the receiving basin.

Moreover, there is a clear relationship between the position of bays and harbours and their structural control, nearly orthogonal ESE­WNW and NNE­SSE directed.

Therefore, besides the bay morphology being associated with this structural control, it was shaped by glacial and periglacial activity and by the basin sedimentary mechanisms.

The morphology of the beach is controlled by factors as coastal topography, type of associated glacier, amount and type of available sediments, and the energy being dissipated at the beach. Furthermore, tides are stronger agents than waves, which are particulary important during storm episodes.

Beaches at levels less than 18m were studied. The raised beaches from 6m and 18m, related to extended stillstands or transgressions, were identified as the principal ones.

Four "glaciomarine" sedimentation zones were defined in the bay, namely: proximal, middle, distal and residual ones. In the coastal environment, the present beach, raised beaches, ice­contact zone and meltwater channel zones were recognized along the coastline.

RECONSTITUIÇÃO PALEOAMBIENTAL DA REGIÃO DO BANHADO DO COLÉGIO, CAMAQUÃ, RS

PALAEOENVIRONMENTAL RECONSTITUTION OF THE BANHADO DO COLÉGIO REGION, CAMAQUÃ, RS

Ana Luísa Vietti Bitencourt (1992)

Adviser: Jorge Alberto Villwock

Associated Adviser: Pedro Ignácio Schmitz

Abstract

The study of the paleoenvironmental reconstitution of the Banhado do Colégio area, Camaquã municipality, involves the interdisciplinary approach of Quaternary Geology and Archaeology, introducing the archaeologic sites in the environmental context of the area.

This approach includes the observation of three scales: the Macro­environmental, where the general aspects of the Coastal Province of Rio Grande do Sul are reported, the Meso­environmental, with the approach of the geomorphological andgeological aspects of the area, related to two systems: a fan­delta an a lagoonal, both controled by positive and negative oscilations of the sea­level during the Quaternary; and the Micro­environmental, which characterizes the archaeologic sites and their distribution in the Meso­ ­environment.

The chart of the environmental reconstitution presents the proposed compartimentation of the area with its systems of fan­delta and lagoon depositions, and the superposition of the archaeologic sites.