Elemental Geochemistry and Organic Carbon Content in the Boquillas Formation, West Texas




Oseji, Samuel E.

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The Boquillas Formation, a Late Cretaceous formation, was deposited at a time when a significant proportion of the modern-day Texas was submerged under the sea, succeeded by the deposition of marine siliciclastic and carbonate materials on the shelf of the northern margin of the Gulf of Mexico. During this time, the Gulf of Mexico experienced reducing conditions, which includes the Ocean Anoxic Event (OAE 2) occurring at the Cenomanian to Turonian boundary (93 Ma). Geochemical analysis of the Boquillas Formation deposits allows researchers to reconstruct the paleoenvironmental conditions at the time of deposition, as well as its organic matter concentration. X-ray fluorescence spectroscopy and Rock-Eval pyrolysis process were applied to 25 samples collected from a 109 m exposed Ernst Tinaja section at the Big Bend National Park (BBNP). An evaluation of the geochemical dataset using proxies for redox conditions, detrital input, productivity, and nutrient supply, as well as Rock-Eval parameters such as TOC, Tmax, and Kerogen type/quality, reveals that the Boquillas Formation was deposited in an anoxic and organic-rich environment. Statistical analysis techniques such as crossplot and principal component analysis (PCA) were applied to the data set, and they provided correlations among the data sets and defined various geochemical trends within the data set. This study achieved two primary goals, First, using geochemical analysis (XRF) to highlight fluctuations in the Boquillas Formation compositions. Second, using Rock-Eval pyrolysis to assess and examine the extent of organic carbon enrichment in the Boquillas Formation.


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Rock-Eval parameters, Boquillas Formation, Paleoenvironmental conditions, Organic carbon enrichment