A MULTI-INDICATOR APPROACH TO UNDERSTANDING THE DIAGENESIS OF CARBONATES IN PENNSYLVANIAN MUDROCKS OF THE MIDLAND BASIN

• Main Author: Reis, Alex J.
• Format: Others
• Published: UKnowledge 2018
• Subjects: Carbonate Diagenesis; Dolomitization; Stable Isotope Analysis; Midland Basin; Geochemistry; Geology; Stratigraphy
• Online Access: https://uknowledge.uky.edu/ees_etds/56; https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1064&context=ees_etds

The Late Pennsylvanian was a time of frequent, rapid glacioeustatic sea-level changes. These changes were recorded in the Wolfcamp D Formation of the Midland Basin as a series of cyclothems similar to those studied in the Midcontinent region (e.g., Algeo and Heckel, 2008). This study focuses on identifying the mechanisms and controls on carbonate deposition and diagenesis through the Upper Pennsylvanian Wolfcamp D Formation and evaluating the potential for these layers to be stratigraphically significant. A stepwise progression of diagenetic processes was identified through the use of δ13Ccarb and δ18Ocarb, bulk geochemical and petrographic analysis, and scanning electron microscopy. Carbonate deposition and early-burial diagenesis appears to be strongly influenced by frequent changes in sea-level and benthic redox conditions. The transition to deep-burial diagenesis was controlled by the thermal gradient in the basin and the extent of diagenesis by the amount of clays and organic matter in the surrounding mudrocks. Further diagenesis was induced through interactions with a brine following clay diagenesis. The presence of multiple phases of diagenesis in this system further highlights the need for several lines of inquiry when evaluating the post-depositional evolution of carbonates in a mud-rich setting.