The morphological architecture and distribution of modern and ancient carbonate systems has been shown to follow spatial-self-organization, however, limited studies describe the morphometrics of microbial carbonates. Upper Cambrian microbial-build-ups outcropping in Central Texas, are exposed laterally (plan view), enabling a study of their morphological architecture and spatial distribution. Drone imagery was acquired to capture the outcrop features and develop a digital terrain model (cm scale resolution) for a bedding plane outcrop (600 × 200 m in size). Four scales of microbial growth (S1- few dm, S2- few m, S3- few tens of m, and S4- few hundreds of m) were identified and mapped. A series of morphometric analysis including Ripley's k, univariate, multivariate, and grouping were conducted and results demonstrate that, the scales S1, S2, and S3 display clustering and the spatial organization of microbial-buildups is naturally organized and not random. Further, as the size of the build-ups increases (from S1–S4), the anisotropy (length/width) increases, their shape becomes oblong, and they become aligned (S2–S4) with the inferred regional winds and tide-associated currents (NE-SW according to the present geography). The S1 scale does not align itself with the regional currents; instead, the build-ups behaved as a baffle during growth, and modified the currents locally, leading to preferential alignment at the edges within S2. As the scales increases in sizes (S2, S3, S4), there is competition for space, and due to regional currents, the larger scales preferentially align parallel to high-energy currents. The trends and spatial relationships identified in this study are particularly relevant and provide a scenario for sub-seismic scale heterogeneities for subsurface microbial hydrocarbon reservoirs.
|Original language||English (US)|
|Journal||Marine and Petroleum Geology|
|State||Published - Jul 18 2020|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research was conducted as a part of the Rice/Trinity Industry Microbial Consortium (funded by Shell, Statoil, Chevron and ConocoPhillips). Special thanks to Chevron Energy Technology Company where the quantitative interrogation aspects of our studies of the build-ups were initiated as a summer internship project for the senior author. Part of this research was possible because of newly accessible outcrops on private lands. We are grateful to owners Don and Rosie Shepard and caretakers Mark and Priscilla Krauss of Eagle Ridge Ranch, and Gene and Patsy Zesch, and Scott Zesch for allowing us to conduct research on their ranches. We would also like to thank the Reviewers, whose critical comments have helped us considerably improve this manuscript as well as Dr. Jeff Dravis for his comments and suggestions throughout the research project. The authors declare no conflicts of interest from their affiliations or funding.