Application of XRF, Biostratigraphic, and Carbon Isotope Data to Establish a Sequence Stratigraphic Framework and Depositional Facies Model for the Burnt Bluff Group, Michigan Basin, U.S.A.

Abstract

The Burnt Bluff Group (BBG) is one of several hydrocarbon-producing carbonate units in the Michigan Basin. The BBG has been described in numerous outcrop and quarry studies in the northern part of the basin, but the central basin to the south has received far less attention. The BBG transitions from shallow subtidal and peritidal facies in the north to deep open marine facies in the south. In the north, three formations have been identified, including the Lime Island, Byron, and Hendricks. In the south, however, only one texturally homogeneous carbonate mudstone unit, which is informally called the “Manistique like unit,” has been identified. Due to the homogeneity of the deep water facies, conventional approaches are unable to provide helpful information regarding the sequence stratigraphic relationship between the shelf and basin deposits. To circumvent this problem, the current study integrates core description, energy dispersive x-ray fluorescence (ED-XRF) elemental data, conodont biostratigraphy, and stable carbon isotopes to establish sequence stratigraphic relationships across the basin.

ED-XRF was used to identify elemental variability within the “Manistique like unit.” Particular focus was given to continental proxy elements (e.g., Al, Si, K, Ti, Zr), which are interpreted to reflect the input of terrigenous material into the basin. Continental proxy elements exhibit systematic variations that can be correlated between three wells in central basin suggesting that elemental variations do not reflect local changes, but rather changing basin wide conditions. Positive correlation (R²>0.8) between Al-K, Ti-Zr, Al-Si, and Al-Zr are consistent with a detrital, continental origin for the proxy elements. Elemental variability was also used to identify five unique chemofacies, which are interpreted to represent changes in relative sea-level. Chemofacies successions show recurring changes that are interpreted to reflect depositional cyclicity. Elemental data also show a general pattern of higher concentrations of the continental proxy elements as well as higher [Fe] and [Sr] in the lower part of the BBG and lower concentrations in the upper part. These patterns may provide some constraint on shelf to basin correlations, but need to be evaluated further. Pending conodont and carbon isotope data will be used to refine age constraints, and to help establish a sequence stratigraphic framework for the BBG.

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