High-resolution taphonomy and sequence stratigraphy of internally complex, bakevelliid-dominated coquinas from the Aptian Romualdo Formation, Araripe Basin, NE Brazil

• Published in: Marine and Petroleum Geology
• Main Authors: Rodrigues, M. G., Varejao, F. G., Matos, S. A., Fuersich, F. T., Warren, L. V., Assine, M. L., Simoes, M. G.
• Other Authors: Universidade Estadual Paulista (UNESP)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier B.V. 2022
• Subjects: Epeiric sea coquinas; Multi-event shell beds; High-resolution sequence stratigraphy; Lower cretaceous; Claro; South Atlantic Ocean
• Online Access: http://hdl.handle.net/11449/237799; https://doi.org/10.1016/j.marpetgeo.2022.105814

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Petrobras Center for Geosciences Applied to Petroleum Geology -UNESPetro, IGCE/Unesp/Rio Claro P,D&I Clause of ANP Resolution Processo FAPESP: 18/01750-7 Processo FAPESP: 16/13214-7 Processo FAPESP: 17/20803-1 CNPq: 401039/2014-5 CNPq: 304800/2017-1 Petrobras: 2014/00519-9 P,D&I Clause of ANP Resolution: 50/2015 The Aptian Romualdo Formation (Araripe Basin, NE Brazil) was deposited in a restricted epeiric sea, during the opening of the South Atlantic Ocean, with a coeval record to that in the Brazilian Pre-Salt succession. The upper part of the Romualdo Formation encompasses the Highstand Systems Tract of a third-order stratigraphic sequence, and contains shell beds interbedded with shale, siltstone, and fine-grained sandstone. Based on distinct taphonomic features (shell sorting, fragmentation, abrasion, rounding, and orientation), sedimentological criteria (shell abundance, type of matrix, sedimentary structures, and presence/absence of quartz grains), and stratigraphic attributes (bed thickness, geometry, contacts), the paleoenvironmental conditions and the bed-bybed accumulation history of the coquinas is disentangled. Eight carbonate microfacies were recognized, including ostracod carbonate mudstone, bivalve-gastropod wackestone, gastropod-bivalve packstone, bivalvegastropod grainstone, bivalve-gastropod floatstone, bivalve-gastropod rudstone, bakevelliid floatstone, and bakevelliid rudstone, which are organized in six, cm-thick shell concentrations. Mudstone and wackestone facies mark the settling of carbonate muds without significant bottom currents and wave action, probably below storm wave base, whereas packstone, floatstone, and rudstone, with fragmented, rounded, and oriented shells, were deposited in agitated waters, between the fair-weather and the storm wave bases. Ripple cross-laminated grainstone is interpreted as high-energy facies ...