Figure 2 - uploaded by Luis Encarnación Silva
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The Agua Nueva Formation in the study area. a) Outcrop, b) laminated limestone, and c) pyrite lenses (SP) indicated by an arrow. Scale bar = 1 cm.
Source publication
The purpose of this work is to provide a description of biomorphic structures found in sedimentary pyrite present in the organic-rich marine limestone of the Agua Nueva Formation (Upper Cenomanian, Upper Cretaceous), central Mexico, using scanning electron microscope images. Six types of biomorphic structures were found and interpreted as coccoids...
Context in source publication
Context 1
... Agua Nueva Formation in the study area (Figure 2) has been previously described and studied by several authors (MaldonadoKoerdell, 1956;Suter, 1990;Blanco-Piñón et al., 2008, 2014Blanco et al., 2010Blanco et al., , 2011Castañeda-Posadas et al., 2014;Nuñez-Useche et al., 2016) for paleontological and geochemical purposes. In summary, this lithologic unit consists predominantly of alternating fossilifer- ous, organic matter-rich, laminated, dark gray limestone and non- laminated, organic matter-poor limestone in decimeter-thick beds (10 to 30 cm) with occasional centimetric beds (5 cm) of brown shale that show no apparent internal structures. The section also includes 2 to 4 cm-thick intermittent light olive-colored bentonite layers. Intermittent layers of ca. 5 cm-thick black chert are present in both the laminated and non-laminated limestone. The pyrite analyzed in this work was collected from the first six meters of the section, cor- responding to the Cenomanian ( Núñez-Useche et al., 2016) based on the presence of the planktonic foraminifera Rotalipora cushmani and Thalmanninella greenhornensis (observation of the authors), as sug- gested by BouDagher-Fadel (2013). Pyrite occurs as 1 to 2 cm-thick lenses within the well-laminated dark limestone and is parallel to the ...
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