HR: 0800h
AN: B41A-0033    [Abstracts]
TI: Unraveling Molecular Mechanisms for the Unusual Fossil Preservation and Biomineralization Pathways in Tlayúa, the Mexican Solenhofen
AU: * Cervini-Silva, J
EM: jcervini@igg.unam.mx
AF: Instituto de Geografia, UNAM, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04330, Mexico
AU: Fakra, S
EM: SFakra@lbl.gov
AF: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
AU: Alvarado-Ortega, J
AF: Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04510, Mexico
AU: Cornejo-Garrido, H
AF: Instituto de Geografia, UNAM, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04330, Mexico
AU: Marcus, M
AF: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
AU: Hao, Z
AF: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
AU: Espinosa-Arruberena, L
AF: Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04510, Mexico
AU: Banfield, J
AF: Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, United States
AB: The Tlayúa slurry constitutes the most important paleontological locality in the American continent, and constitutes the second most important locality in its genre worldwide. The importance of Tlayúa strives in the fact that a great diversity of marine and terrestrial fossils in perfect state of preservation have been found, with ages surpassing 115 million yrs. Paleomagnetic determinations and biostratigraphic determinations conducted in amonites and belemnites indicate that the formation of the Tlayúa slurry dates back to the late Albian. On the other hand, fish, reptiles, invertebrates, and vegetables fossil specimens have been found to date back to the Mesozoic Era. Because of this fact is unprecedented worldwide, Tlayúa is nowadays considered patrimony for the humanity. One of the most accepted hypothesis for explaining Tlayúa's formation relies on the deposition of sediments and fauna on a shallow platform of a tropical sea. A similar geographic place is located in Solenhofen, Germany, where slurries have been exploited for more than 200 yrs with a production of approximately 500 species. Remarkably, in the Tepexi del Rio region for the past 20 yrs more than 5,000 fossil specimens representing more than 200 species have been collected alone. An exceptional specimen preservation found in Tlayúa has been attributed to restricted circulation of water resulting in an anaerobic and/or hypersaline environment, coupled with the general absence of infaunal species. There were periods when the deposition site supported a rich planktontic community. Large quantities of calcareous ooze were produced, resulting in rapid burial of the organisms. The presence of diagnostic terrestrial and freshwater organisms, including arachnids, insects, lizards, and chelonians, along with typical marine fauna, suggests that Tlayúa lagoon had periodic freshwater inflow, in addition to the strong marine, lagoonal, and reefal influence. Some organisms were transported into the lagoon when the barrier was breached, probably during periods of heavy rains and hurricanes, or during high tides. Additionally, some fishes from Tlayua have been found to have affinities with recent families known to inhabit brackish and freshwater environments. Some of these fish preserve gut contents. Preliminary analysis of the intestinal content of these fishes has resulted in identification of freshwater insects and fern fragments. This work addresses for the first time the study of chemical and biological mechanisms contributing to fossil preservation and biomineralization pathways prevailing in Tlayúa using synchrotron techniques (XRF, - XRD, 3D--IR, XANES/EXAFS, STxM). We present chemical composition data collected from a fish egg's interior in search of fossilized structures. We also present data from well-preserved soft tissue collected from a fish soon to be named Michin scernai (newly identified specie, thus the name cannot be applied formally just yet). This fish is a Pachyrhizodontide, from the telesteos incertae sedis group already extinct. This particular sample was collected from the gastric cavity, precisely where female fish store the eggs before laying.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0410 Biodiversity
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
SC: Biogeosciences [B]
MN: 2007 Fall Meeting