Climatic and tectonic sea-level gauge for Midcontinent Pennsylvanian cyclothems

Abstract

New sedimentological determinations suggest that Pennsylvanian sea-level change ranged from as little as 40 m to as much as 160 m, depending on which model establishes the deepest water facies of a Midcontinent cyclothem. Average sedimentological estimates of sea-level change for models of Heckel and Gerhard are 96.4 m and 86.0 m, respectively. In the Midcontinent, tectonic subsidence contributed 5% to 20% of the total Pennsylvanian sea-level change in platform areas and basin depocenters. Additional change in sea level was controlled by short-term glacial eustasy (nearly 70% of sea-level change) and long-term climate change (nearly 15% of sea-level change). These findings suggest that away from orogenic belts, climatic change is the principal driving mechanism controlling sea-level change, whereas within orogenic belts, climate becomes more subordinate to tectonic processes that influenced Pennsylvanian sea-level change, even though indicators of climatic change reportedly are preserved.