Late Guadalupian Evolution of the Delaware Basin: Insights From Stable Isotope and Trace Element Geochemistry

Abstract

Accurate characterization of mixed carbonate/evaporite deposits requires integration of textural observations with geochemical data. In restricted basins, physical and chemical changes in the water column exert a first order influence on source rock accumulation, carbonate reservoir characteristics, and evaporite seal deposition. Once calibrated, geochemical proxies for basin water chemistry can serve as powerful tools for petroleum systems analysis. However, the assessment of both spatial and temporal variability at the basin scale presents a significant challenge in the ongoing development of these geochemical proxies.

The high-resolution stratigraphic framework of the Delaware Basin of Texas and New Mexico offers a unique opportunity to test and refine models of basin water evolution. Because sequence stratigraphy and biostratigraphy constrain shelf-to-basin correlations, geochemical data can be placed into their proper spatial and temporal context, allowing for a more holistic picture of how basin water evolved during closure of the basin.

Although previous work has explored the geochemistry of Late Guadalupian/Ochoan deposits, the current effort focuses on collecting trace element data for the interpretation of paleoredox conditions in the water column. This approach, which has proven to be an important tool for characterizing source rocks and resource plays, can logically be extended to other restricted settings such as evaporite basins. The overall goal is to use the Delaware Basin to refine concepts and tools that can be applied to solving geologic problems in other complex settings such as lacustrine systems.

Geochemical data and facies relationships suggest a link between basin water chemistry and sea level changes during the entirety of the Guadalupian. This link is supported analogies to modern silled basins where changes in sea level and thus recharge across the sill can control nutrient input, circulation, and bottom water oxygenation. In light of these relationships, the filling of the Delaware Basin with basin-centered evaporites at the end of the Guadalupian likely represents the culmination of a more gradual, cyclic evolution towards basin restriction. This study provides an example of how basin water chemistry and circulation can act in conjunction with sea level to influence carbonate facies and early diagenetic products.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018