Paleoenvironmental constraints on shallow-marine carbonate production in central and West Texas during the Albian (Early Cretaceous)

Abstract

The Albian Glen Rose Formation in central and west Texas records carbonate sedimentation in a broad epicontinental sea partly contemporaneous with Oceanic Anoxic Event 1b. The paleogeographic setting of the Comanche Platform facilitated the deposition of carbonate sediments that resulted in carbonate matrix-rich facies, with various amounts of allochems, which permitted the interpretation of shallow lagoon depositional settings. Geochemical proxies for environmental conditions (nutrient supply, detrital input, redox conditions) were calculated from the elemental geochemical analysis of samples, while their carbon and oxygen isotope composition was used to evaluate the impact of diagenesis. The statistical analysis of this dataset helps identify three intervals within the Glen Rose Formation where the matrix-rich carbonate sedimentation was modulated by environmental parameters. First, the strong correlation between MgO concentration and δ18O vectors on a Principal Component Analysis for the whole dataset confirms the deposition of dolomitic series with stromatolites in a restricted environment. Second, moderately high nutrient input and low detrital flux suggest that part of the sedimentation in west Texas was affected by upwelling. Third, mesotrophic conditions associated with a patch reef made of rudist bivalves support their suspension feeder ecological behavior. Conclusions drawn for this research may apply to other shallow-marine series deposited in broad epicontinental seas affected by greenhouse conditions.