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47-595: The basin formed during the opening of the South Atlantic Ocean in the Late Jurassic and Cretaceous periods alongside other basins in the Brazilian coast. Studies of the basin's geology date back to the first half of the 19th century, when J. Henderson in 1821 published preliminary notes on the region's geology, but the first geological and paleontological surveys were carried out in 1865–1866 by

94-406: A meandering river , which has a single sinuous channel. It is also distinct from an anastomosing river , which consist of multiple interweaving semi-permanent channels which are separated by floodplain rather than channel bars; these channels may themselves be braided. The physical processes that determine whether a river will be braided or meandering are not fully understood. However, there

141-542: A meandering profile. A stream with cohesive banks that are resistant to erosion will form narrow, deep, meandering channels, whereas a stream with highly erodible banks will form wide, shallow channels, preventing the helical flow of the water necessary for meandering and resulting in the formation of braided channels. Braided rivers occur in many environments, but are most common in wide valleys associated with mountainous regions or their piedmonts or in areas of coarse-grained sediments and limited growth of vegetation near

188-404: A dendritic system, or of cohesive sediments with no bedload transport. Meanders fully develop only when the river banks are sufficiently stabilized to limit lateral flow. An increase in suspended sediment relative to bedload allows the deposition of fine erosion -resistant material on the inside of a curve, which accentuated the curve and in some instances, causes a river to shift from a braided to

235-603: A fluvio- deltaic-lacustrine environment. Fossils are poorly preserved but abundant, specially in the Morro do Chaves Member. The name derives from the Coqueiro Seco-01 well in Alagoas. It replaces the older name, Jiquiá Formation. Early Aptian in origin. It consists of characteristic grey to green shales formed during a widespread transgression in the area. Fossils are not common in the formation, however an abundance of

282-471: A great deal of data about the land and the people, contributing to new knowledge about the flora , the fauna , minerals, geography , linguistics and ethnography . He was an accomplished draftsman and illustrator and musician. In his last voyage he collected more than 500,000 specimens , which were donated to the National Museum of Rio de Janeiro , where he worked as the founder and director of

329-506: A lacustrine environment. Fossils of non-marine ostracods, such as Bisulcocypris pricei and Darwinula aff. oblonga . The formation was named after the village of Bananeiras in Sergipe. Late Jurassic to Early Cretaceous in origin. Composed by medium to coarse-grained sandstones with tabular and channelled cross-stratification. The sediments were deposited by a braided fluvial system, locally with eolian reworking. Large conifer trunks of

376-484: A network of river channels separated by small, often temporary, islands called braid bars or, in British English usage, aits or eyots . Braided streams tend to occur in rivers with high sediment loads or coarse grain sizes, and in rivers with steeper slopes than typical rivers with straight or meandering channel patterns. They are also associated with rivers with rapid and frequent variation in

423-641: A number of subsequent studies from 1961 to 1968. The geological evolution of the basin represents 5 tectonic stages: syneclise, pre-rift, rift, transitional and drift. 1) Syneclise stage - Late Carboniferous to Early Permian - It is represented by the Batinga Formation , which probably was of glacial origin, which comprises siliciclastic rocks, and the Aracaré Formation , comprising eolian sandstones, shales and lacustrine algal laminites. 2) Pre-rift stage - Late Jurassic - Represented by

470-426: A straight channel. Also important to channel development is the proportion of suspended load sediment to bed load . An increase in suspended sediment allowed for the deposition of fine erosion -resistant material on the inside of a curve, which accentuated the curve and in some instances, caused a river to shift from a braided to a meandering profile. These experimental results were expressed in formulas relating

517-402: A variation in sediment load, provided the amount of water carried by the river is unchanged. A threshold slope was experimentally determined to be 0.016 (ft/ft) for a 0.15 cu ft/s (0.0042 m /s) stream with poorly sorted coarse sand. Any slope over this threshold created a braided stream, while any slope under the threshold created a meandering stream or – for very low slopes –

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564-597: A warm and dry desertic environment and shore bordering a large lake. The name Aracaré originates from the Aracaré Hill, 2 km south of the town of Neópolis . Late Jurassic in origin. Composed of fine to medium-grained sandstones, possibly formed in a braided fluvial system. The formation is not exposed and no fossils have been found. It was named after the Candeeiro-01 well (1-CO-1-AL) in Alagoas. Late Jurassic in origin. Composed by red shales deposited in

611-576: A year. Hartt also studied the geology of New Brunswick , and devoted special attention to the Devonian shales, in which he discovered an abundance of land plants and insects. In 1861, Hartt started to work as a student assistant for Louis Agassiz at the Museum of Comparative Zoology , Harvard University . This work lasted until 1864, when he received an appointment on the geological survey of New Brunswick. In 1865 he accompanied Agassiz to Brazil in

658-559: Is composed of a cyclic alternation of marls and shales. Fossils of ammonites are bountiful in this formation, alongside fossils of other molluscs and fish. The Formation was named after the municipality of Riachuelo. Early Cenomanian to Middle Coniacian in origin. The formation consists of the Sapucari and Aracaju members, the Sapucari Member is formed of calcilutites and subordinately carbonate breccias that grade basinward onto

705-432: Is thought to had been braided and meandering fluvial system . The formation was named after the town of Estância in southern Sergipe. Late Carboniferous to Early Permian in origin. The siliciclastic rocks which compose the formation where formed under a glacio-marine environment. It is divided into 3 member: The Mulungu, Atalaia and Boaciaca members. The Mulungu Member is represented by conglomerates and diamictites,

752-403: Is wide agreement that a river becomes braided when it carries an abundant supply of sediments. Experiments with flumes suggest that a river becomes braided when a threshold level of sediment load or slope is reached. On timescales long enough for the river to evolve, a sustained increase in sediment load will increase the bed slope of the river, so that a variation of slope is equivalent to

799-548: The Candeeiro Formation , Bananeiras Formation and Serraria Formation , when crustal uplift resulted in a series of depressions which were filled by fluvial and lacustrine sediments. 3) Rift stage - Early Cretaceous - Represented by the Rio Pitanga Formation , Penedo Formation , Barra de Itiúba Formation and Coqueiro Seco Formation , increasing tectonism led to the formation of a rift-valley,

846-583: The Rakaia and Waitaki Rivers of New Zealand are not aggrading, due to retreating shorelines, but are nonetheless braided rivers. Variable discharge has also been identified as important in braided rivers, but this may be primarily due to the tendency for frequent floods to reduce bank vegetation and destabilize the banks, rather than because variable discharge is an essential part of braided river formation. Numerical models suggest that bedload transport (movement of sediment particles by rolling or bouncing along

893-617: The Thayer Expedition . Agassiz was mainly concerned with collecting fish on the expedition through the Amazonian basin. He also hypothesized that Brazil had also been affected by the Last Glacial Maximum (LGM), so supported field work to find evidence supporting glaciation, such as gravel beds. His close assistant Hartt instead found evidence that other factors such as organic decay caused specific features in

940-446: The 1859 Darwinian evolutionary theory , in contrast to the multiple creation theory it proposed to replace. From a scientific point of view, Darwinism could potentially resolve inconsistencies in the multiple creation narrative, just as multiple creation theory was an attempt to resolve inconsistencies in the single creation theory. The inconsistencies were facts that could not be compellingly explained by each theory. Evolutionary theory

987-591: The 21st century the refuge mechanism has been diminished as a possible explanation by research that determined sufficient rainfall maintained a more complete ecosystem, which increases the likelihood of a more complex mosaic mechanism to explain the variations in Hartt's specimens. The ancient pollen data in the Bolivian rainforest of the Amazonian basin indicates that it was savannah during the LGM. One of Hartt's students,

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1034-598: The American geologist Orville Adalbert Derby (1851–1915), succeeded him at the National Museum , after having accompanied him in two of the Morgan Expeditions (1870 and 1871) and having worked with him at the Imperial Commission. The Armoured Catfish genus Harttia is named after him. Braided river A braided river (also called braided channel or braided stream ) consists of

1081-485: The American palaeontologist Charles A. White, describing ammonites, bivalves, gastropods and echinoids. John Casper Branner published in 1890 a report on the Sergipe-Alagoas Basin about the localities of White's materials. Ralph Sopper published in 1914 the first geological map of the basin, but a more detailed map was published in 1924 by the “Serviço Geológico e Mineralógico do Brasil”. Research of

1128-730: The Atalaia Member consists of immature coarse-grained sandstones and the Boacica Member is composed by laminated siltstones, sandstones and conglomerates deposited by deltaic fans. The formation was named after he village of Batinga in the northwestern part of the Sergipe Sub-basin. Permian in origin. Composed by mature coarse-grained sandstones with large cross-stratification sets, associated with silicified oolitic-oncolitic calcarenites, algal mats and stromatolites. The original surroundings where suggested to have been

1175-637: The Basin received strong motivation when search for petroleum begun in the 1940s, resulting in detailed maps and new fossil collections. Since 1953, the Brazilian Petroleum Company, PETROBRAS , produced various reports with the aim of improving knowledge of the region during the search for petroleum. Biostratigraphic studies by Karl Beurlen established a zonation of the Aptian - Albian Riachuelo Formation based on ammonites. He also published

1222-403: The Brazilian landscape. In the 20th century, extensive field work by other scientists mapped a vast ancient savannah that had separated the Amazonian rainforest into two separate ecosystems during the glaciation of other regions. The separation of ecosystems could theoretically support increased speciation. But in the 21st century, additional research was funded to answer hypothetical concerns about

1269-584: The Canadian naturalist Charles Frederick Hartt , a participant of the Thayer Expedition . The results of this expedition were published in the book “Geology and Physical Geography of Brazil” from 1870, where it was described fossils of ammonites and a gastropod from the municipalities of Maruim and Larangeiras . With the Commissão Geológica do Império do Brazil , an expedition from 1875 and 1878 directed by Hartt, important studies were carried by

1316-549: The Penedo Formation. The formation was probably deposited by a deltaic system in a lacustrine environment. Much of the fossils there are of ostracods, like Cypridea and Paracypridea . The formation was named after the Barra de Itiúba village in Alagoas. Early Cretaceous. Composed of coarse to medium-grained sandstones deposited in a fluvial-deltaic environment subject to eolian reworking. The only fossils found in

1363-551: The age of 38. Agassiz died earlier, in 1873, before major discoveries could provide substantial fossil evidence and before the neo-Darwinists improved Darwinism by asserting the Weismann barrier in 1893. Hartt had gathered useful specimens in Brazil that could be explained by the 20th century Darwinian narrative of accelerated evolution, which hypothesized that Amazonian butterflies survived in isolated refuges during ice ages. But in

1410-437: The amount of water they carry, i.e., with " flashy " rivers, and with rivers with weak banks . Braided channels are found in a variety of environments all over the world, including gravelly mountain streams, sand bed rivers, on alluvial fans , on river deltas , and across depositional plains. A braided river consists of a network of multiple shallow channels that diverge and rejoin around ephemeral braid bars . This gives

1457-763: The coastal regions from Bahia to Rio de Janeiro . The large zoological collections he made were later used to prepare his Geology and Physical Geography of Brazil (Boston, 1870). In 1868 he was elected professor of natural history at Vassar College , but later in the same year he accepted a post at Cornell University , in Ithaca , New York, and planned to return to Brazil. Charles married Lucy Cornelia Lynde of Buffalo, New York , in 1869. They had two children, Mary and Rollin. Both children became writers. In all, Hartt participated in four expeditions to Brazil (the Morgan Expeditions) from 1870 to 1878. He collected

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1504-426: The critical slope for braiding to the discharge and grain size. The higher the discharge, the lower the critical slope, while larger grain size yields a higher critical slope. However, these give only an incomplete picture, and numerical simulations have become increasingly important for understanding braided rivers. Aggradation (net deposition of sediments) favors braided rivers, but is not essential. For example,

1551-556: The formation are of ostracods. Its name derives from the town of Penedo on the Rio São Francisco in Alagoas. Hauterivian to early Aptian in origin. Composed of coarse-grained polymictic and alluvial conglomerates. No fossils have been found. The name derives from the Rio Pitanga-01 well (1-RP-1-SE) in Sergipe. Lower Cretaceous in origin. Consists of fine to coarse- grained sandstones and mudstones deposited in

1598-665: The formation include foraminifers, palynomorphs, ostracods, conchostraceans and fish remains. The name Muribeca derives from the town of Muribeca in northern Sergipe, where was found rocks thought to be from this formation. In reality, the rocks are now assigned to the Rio Pitanga Formation, and the Muribeca Formation is not exposed at all. Late Aptian in origin, contemporary with Muribeca. Composed of coarse to fine-grained sandstones, with minor shale intercalations, and conglomerates. Common fossils in this in

1645-686: The late Aptian. Events during the Cenomanian and early Turonian cause the drowning of the Riachuelo platform system. Proterozoic (possibly Cambrian) in origin. Sub-basin Sergipe is composed of metamorphic rocks. Metasediments also occur, possibly of Cambrian origin. Sub-basin Alagoas is composed by granitic rocks from the Pernambuco-Alagoas Massif. Cambrian in origin. Composed by red sandstones and siltstones with mica schists and conglomerate lenses. The depositional environment

1692-602: The newly created rift was filled by an alluvial-fluvial-deltaic system. 4) Transitional stage - Early Aptian - Represented by the Muribeca Formation and Maceió Formation , the transitional stage began when the first marine sediments were deposited. 5) Drift stage - Early to mid Albian - Represented by the Riachuelo Formation , begun in the Albian, even though marine regime was established already in

1739-658: The pollen Afropollis sp. is a characteristic feature of Ponta Verde. It is named after the Ponta Verde-01 well near Maceió. Late Aptian in origin. The Formation is formed by 3 members, the Carmópolis, Ibura and Oiterinhos members. The Carmópolis Member is formed by sandstones with minor intercalations of siltstones and shales and polymictic conglomerates. The Ibura Member contains a succession of halite, sylvinite and carnallite. The Oiteirinhos Member has an alternation of laminated calcilutites and shales. Fossils found in

1786-459: The potential extinction of the entire Amazonian ecosystem during predicted global warming. This field work indicated there were areas in the western lowlands near Lake Pata that retained lush tropical rainforest, so the complete natural history of the Amazonian basin during the LGM is developing a more complex narrative in which Hartt's field work can be expounded. Agassiz and Hartt were also searching in 1865 for evidence that could prove or disprove

1833-546: The river a fancied resemblance to the interwoven strands of a braid . The braid bars, also known as channel bars, branch islands, or accreting islands, are usually unstable and may be completely covered at times of high water. The channels and braid bars are usually highly mobile, with the river layout often changing significantly during flood events. When the islets separating channels are stabilized by vegetation, so that they are more permanent features, they are sometimes called aits or eyots. A braided river differs from

1880-414: The river bottom) is essential to formation of braided rivers, with net erosion of sediments at channel divergences and net deposition at convergences. Braiding is reliably reproduced in simulations whenever there is little lateral constraint on flow and there is significant bedload transport. Braiding is not observed in simulations of the extreme cases of pure scour (no deposition taking place), which produces

1927-814: The section of geology from 1866 to 1867. In 1875, following a suggestion by Hartt, the Emperor Dom Pedro II (1825–1891) established the Imperial Geological Commission. The Commission was closed down after two years of work after losing the Emperor's support. Hartt was joined by his wife and children in Brazil in 1875, but they returned to the United States without him when his wife got pregnant. Hartt died in Rio de Janeiro on 18 March 1878, after contracting yellow fever , at

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1974-520: The shales are of conchostraceans and fish. It's named after the capital of Alagoas, Maceió. Early Aptian to Late Aptian in origin. Composed of conglomerates and coarse-grained arkoses. Late Aptian to Early Cenomanian in origin. The formation is formed by 3 members, the Angico, Maruim and Taquari. The Angico member is composed by siliciclastic conglomerates and sandstones and the Taquari Member

2021-586: The shales of the Aracaju Member. Although they are not as abundant as the Riachuelo Formation, the fossils of this formation are diverse, including ammonites and inoceramids. It was named after a vast valley the cuts the formation. Santonian to Recent in origin. Formed by siltstones and olive-green shales and pale-yellow sandstones. The formation is generally poor on fossil remains, although some outcrops are abundant. The name derives from

2068-554: The small village of Calumbi west of Aracaju. Tertiary to Recent in origin. Composed mostly of medium to coarse sandstones, close to the coast. No fossils have been found in this formation yet. The name derives from the village of Marituba in Alagoas. Composed mostly of bioclastic calcarenites. Most common fossils are fragments of molluscs and foraminifers. Charles Frederick Hartt Charles Frederick Hartt (23 August 1840 in Fredericton, New Brunswick – 18 March 1878)

2115-557: The species Agathoxylon benderi where found in the formation's sandstones. It was named after the small village of Serraria in southern Alagoas. Berriasian to Valanginian in origin. Its fossil record consists of gastropods, bivalve molluscs, remains of Lepidotes fish, crocodylomorph teeth and the oldest occurrences of Spinosauridae in South America . Early Cretaceous in origin. It is composed by succession of shales and fine-grained sandstones that interfingers laterally with

2162-572: Was a Canadian-American geologist, paleontologist and naturalist who specialized in the geology of Brazil . Hartt graduated from Acadia College in Wolfville, Nova Scotia , in 1860, and by his graduation he had made extensive geological explorations in Nova Scotia . In 1860, he accompanied his father, Jarvis William Hartt, to Saint John, New Brunswick , where they established a high school for young women in which Charles Frederick taught for

2209-600: Was not immediately accepted because of a lack of fossil evidence (an issue resolved by discovery of more and more fossil "missing links") and its inability to explain the distribution of species better than multiple creation theory (an issue resolved in the 1960s by plate tectonics ). There were a few inconsistencies such as the Lamarckian idea of inheritance of acquired characteristics that Darwin had accepted and later expanded upon in his writings on heredity . Hartt fell in love with Brazil, and spent 15 months exploring

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