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Type: Artigo de periódico
Title: Depositional mechanisms and architecture of a pre-early Cambrian mixed sand-mud deepwater ramp (Apiuna Unit, South Brazil)
Author: Basilici, G
Abstract: The Apiuna Unit is located in the south of Brazil, in the State of Santa Catarina. It is a deepwater depositional system, which is part of the sedimentary fill of the Itajai Basin, pre-early Cambrian in age, interpreted as a foredeep basin. We have described and interpreted the depositional mechanisms according to the terminology proposed by Mulder and Alexander [Mulder, T., Alexander, J., 2001. The Physical Character of Subaqueous Sedimentary Density Flows and their Deposits. Sedimentology 48 (2), 269-299] and have recognized seven architectural elements. The Apiuna Unit is interpreted as a mixed sand-mud deepwater ramp system. The slope deposits are characterized by laminated argillite with slumped beds. The proximal and medial ramp is characterized by channel-levee systems. The distal ramp shows sandstone sheet, which pass distally into interlayered sandstone/pelite. The sequence development of this ramp unit differs from other known ancient ramp systems. The Apiuna Unit shows at least five phases of sandy input, recording times of progradation or retrogradation of the ramp, interstratified with muddy deposits, related to sand-starved phases. In the upper pail of the succession, the ramp building was interrupted and the sandy deposits are replaced by pelitic slope deposits. The depositional mechanisms have a direct relationship to the architectural elements and the regions of the depositional system. Settling, very low-density turbidity currents and slumps formed the slope deposits. Channel deposits are formed by debris flows, hyperconcentrated density flows and concentrated density flows, in that vertical sequence order. Levee deposits were made of surge-like turbidity flows. Proximal sandstone sheet deposits were formed by concentrated density flows. Distal sandstone sheet deposits are formed by concentrated density flows and surge-like turbidity flows. Surge-like turbidity flows and quasi-steady turbidity flows formed the interchannel deposits. (c) 2006 Elsevier B.V All rights reserved.
Subject: deepwater elastic ramp
sediment gravity flows
architectural elements
Apiuna Unit
ltajai Basin
pre-early Cambrian
Country: Holanda
Editor: Elsevier Science Bv
Citation: Sedimentary Geology. Elsevier Science Bv, v. 187, n. 41732, n. 183, n. 204, 2006.
Rights: fechado
Identifier DOI: 10.1016/j.sedgeo.2005.12.027
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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