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Ordenar por: RelevânciaAutorTítuloAnoImprime registros no formato resumido
Registros recuperados: 4
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Landscape evolution and depositional processes in the Miocene Amazonian Pebas lake/wetland system: evidence from exploratory boreholes in northeastern Peru. Naturalis
Wesselingh, F.P.; Guerrero, J.; Räsänen, M.E.; Romero Pittmann, L.; Vonhof, H.B..
This study of the type and scales of depositional processes and landscape development in western Amazonia during the Miocene is based on the description and interpretation of three boreholes from the Marañon basin (Peru). The Miocene Pebas Formation, and the overlying Marañon Formation and underlying Chambira Formation are lithologically characterised. An age calculation model indicates an Oligocene age for the Chambira Formation, and an Early – early late Miocene age for the Pebas Formation. The base of the Chambira Formation is placed at a sequence boundary and corresponds to the beginning of a regression. The succession was deposited in floodplains included in a RST and a LST under a seasonal climate with a pronounced dry season. The base of the Pebas...
Tipo: Article / Letter to the editor Palavras-chave: Miocene; Marañon basin; Peru; Pebas Formation; Chambira Formation; Stratigraphy; 38.16.
Ano: 2006 URL: http://www.repository.naturalis.nl/record/209731
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Miocene freshwater Mollusca from western Brazilian Amazonia Naturalis
Wesselingh, F.P.; Ranzi, A.; Räsänen, M.E..
Thirteen species of fossil molluscs are reported from the Solimões Formation of western Brazilian Amazonia. Based on mammalian chronology of the Solimões Formation and radiometric ages reported from coeval deposits in adjacent Peru, the age of the fauna is established as Late Miocene. The fauna includes five prosobranch gastropod species, seven pearly freshwater mussel species and one sphaeriid bivalve species. The supposed presence of Pachydon (Corbulidae: Bivalvia) in these deposits is rejected; Pachydon acreanum, whose status has long been uncertain, is transferred to the unionoid genus Callonaia. The Solimões mollusc fauna is entirely composed of obligate freshwater taxa, resembling species-poor modern Amazonian fluvial faunas. The presence of the...
Tipo: Article / Letter to the editor Palavras-chave: Mollusca; Western Amazonia; Miocene; Solimões Formation.; 38.22; 42.73.
Ano: 2006 URL: http://www.repository.naturalis.nl/record/209736
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The nature of aquatic landscapes in the Miocene of western Amazonia: an integrated palaeontological and geochemical approach Naturalis
Wesselingh, F.P.; Kaandorp, R.J.G.; Vonhof, H.B.; Räsänen, M.E.; Renema, W.; Gingras, M..
The Miocene Pebas Formation from the section Santa Rosa de Pichana (Loreto, Peru) was investigated using a combination of analyses of sedimentary facies, molluscan communities and taphonomy, and stable isotopes of both entire shells and growth bands in bivalves. Three sequences, comprising a succession of transgressive, maximum flooding and regressive/prograding intervals, are documented. Molluscs are most common in the transgressive/highstand intervals and are almost absent in regressive/prograding intervals. The fauna is dominated by endemic Pebasian species, such as Pachydon and Dyris spp. The nature of the deposits as well as the availability of oxygen varied in a predictable way within each of the sequences and determined the nature of the...
Tipo: Article / Letter to the editor Palavras-chave: Miocene; Amazonia; Palaeoecology; Sedimentology; Stable isotopes; 38.22; 42.73.
Ano: 2006 URL: http://www.repository.naturalis.nl/record/209732
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The stratigraphy and regional structure of Miocene deposits in western Amazonia (Peru, Colombia and Brazil), with implications for late Neogene landscape evolution Naturalis
Wesselingh, F.P.; Hoorn, M.C.; Guerrero, J.; Räsänen, M.E.; Romero Pittmann, L.; Salo, J.A..
A biozonation based on molluscs is proposed for Miocene deposits of western Amazonia (Peru, Colombia and Brazil), commonly referred to as the Pebas Formation. The new zonation refines existing pollen zonations and provides a key for the quick assessment of the stratigraphic position of Neogene deposits in the field. The regional distribution of twelve mollusc zones reveals a structuring of geological units around the broad Iquitos-Araracuara anteclise. The structure of the subsurface appears to have been a major factor in the determination of present-day second and lower order river courses in the study area. Based on this work a biostratigraphic framework for Miocene deposits of western Amazonia, including fossiliferous deposits from adjacent basins...
Tipo: Article / Letter to the editor Palavras-chave: Stratigraphy; Mollusca; Miocene; Western Amazonia; Pebas Formation; 42.73; 38.22.
Ano: 2006 URL: http://www.repository.naturalis.nl/record/209729
Registros recuperados: 4
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