Microbialite fields developed in a protected rocky coastline: The shallow carbonate ramp of the Aptian Romualdo Formation (Araripe Basin, NE Brazil)

Author(s)

Varejao, F. G. ^[1] ; Fuersich, F. T. ^[2] ; Warren, V, L. ; Matos, S. A. ^[3] ; Rodrigues, M. G. ^{[3, 4]} ; Assine, M. L. ^[4] ; Sales, A. M. F. ^[5] ; Simoes, M. G. ^[3]

Affiliation

^[1] Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Ave 24A, 1515, BR-12506900 Rio Claro - Brazil

^[2] Friedrich Alexander Univ Erlangen Nurnberg, FG Palaoumwelt, GeoZentrum Nordbayern, Loewenichstr 28, D-91054 Erlangen - Germany

^[3] Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP - Brazil

^[4] Warren, L., V, Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Ave 24A, 1515, BR-12506900 Rio Claro - Brazil

^[5] Univ Reg Cariri, Dept Ciencias Biol, Campus Pimenta 1161, BR-63100000 Crato - Brazil

• Document type: Journal article
• Source: SEDIMENTARY GEOLOGY; v. 389, p. 103-120, JUL 1 2019.
• Web of Science Citations: 0

Abstract

The Aptian Romualdo Formation is a siliciclastic-dominated sedimentary unit recording the last marine ingression within the Cretaceous interior basins of northeastern Brazil. At the western margin of the Araripe Basin, rocks of the Romualdo Formation are mainly represented by carbonates resting abruptly over the Proterozoic crystalline basement. Detailed mapping and stratigraphic analysis revealed two stromatolite fields that were described and discussed for the first time. Several bioherms, biostromes and isolated stromatolites characterized by distinct microbialite morphologies associated with echinoid-rich strata have been identified, suggesting that hypersalinity, water depth and hydraulic conditions were the main factors controlling stromatolite morphogenesis. A cm-thick amalgamated bivalve rudstone, resting directly on the basement and representing a shell concentration formed above the fair-weather wave base was also recorded. Based on the regional distribution of the stromatolite types and associated sedimentary fades, we interpret the depositional environment as a local low gradient carbonate ramp deepening to the east. Our data robustly indicated that the western rocky shorelines of the Araripe Basin during the Aptian were populated by microbial mats and stromatolites in a condition analogous to the modern world-famous Hamelin Pool, Shark Bay, Western Australia. Finally, the development of stromatolites and echinoid-bearing microbialites at the western margin of the basin may be correlated with the formation of bakevelliid- and cassiopid-rich shell beds in the upper part of the Romualdo Formation at the eastern margin. (C) 2019 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 14/00519-9 - Centralities of night-time leisure in the city of São Carlos-SP and the interface relations
• Grantee: Tiago Ferreira Lopes Machado
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 16/13214-7 - Multi-proxy approach of the mixed carbonate-siliciclast Crato Formation: sedimentary evolution, paleogeography and tectonics
• Grantee: Filipe Giovanini Varejão
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/20803-1 - Stratigraphic and Paleoenvironmental Context of the Macroinvertebrate Assemblages of the Romualdo Formation, Cretaceous, Araripe Basin, and its Paleogeographic Implications
• Grantee: Suzana Aparecida Matos da Silva
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/01750-7 - Bakevelliidae bivalves of the Romualdo Formation (Alagoas stage, Lower Cretaceous), Araripe Basin, Brazil: paleoenvironmental and paleogeographic significance
• Grantee: Mariza Gomes Rodrigues
• Support Opportunities: Scholarships in Brazil - Master