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标题：Microfacies and diagenetic evolution of the limestones of the upper part of the Crato Formation, Araripe Basin, northeastern Brazil
其他标题：Microfacies and diagenetic evolution of the limestones of the upper part of the Crato Formation, Araripe Basin, northeastern Brazil
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作者：Cabral, Flávia Araújo de Arruda ; Silveira, Ana Claúdia da ; Ramos, Germano Mário Silva 等
期刊名称：Brazilian Journal of Geology
印刷版ISSN：2317-4889
出版年度：2019
卷号：49
期号：1
页码：1-13
DOI：10.1590/2317-4889201920180097
出版社：Sociedade Brasileira de Geologia
摘要：This paper presents the results of a petrographic and diagenetic study of the laminated limestones of the upper part of the Aptian to Albian Crato Formation, northeast of Brazil. The applied techniques were optical microscopy, cathodoluminescence and scanning electron microscopy (SEM) coupled to a wavelength-dispersive spectrometer (WDS). Petrographic analysis has revealed that most of the laminated limestones are calcilutites with a dominance of a micritic matrix, indicating a low-energy depositional environment. Microstructures such as microfaults, microfractures, microslumps, and loop bedding were observed. Based on textural, structural and paleontological features, seven microfacies were recognized: massive limestone, limestone with parallel laminations, limestone with undulated laminations, limestone with slumps, limestone with loop bedding, limestone with ostracods and limestone with peloids. In addition, the processes of cementation, dissolution, replacement, recrystallization and compaction, which are related to different diagenetic stages, were also recognized. The diagenetic constituents found in the sections include calcite, pyrite, silica and sulfates. We can conclude that a large part of the microstructures (microfaults, microfractures, microslumps and loop bedding) can be related to local seismicity, probably due to the reactivation of the Patos Shear Zone. The diagenetic constituents indicate an early to late diagenesis (eogenetic, mesogenetic and telogenetic stage).
关键词：Crato Formation; laminated limestones; diagenesis; Araripe Basin.
其他关键词：Crato Formation;laminated limestones;diagenesis;Araripe Basin