Influence of Organic Matter Source, Abundance, and Growth Habit on Depositional Textures and Associated Pore Attributes of Hypersaline Lacustrine Microbial Deposits (Holocene, Bahamas)

Abstract

Discovery of lacustrine microbialite reservoirs in South Atlantic pre-salt has motivated the search for analogs for perspectives on their deposition and initial porosity. Although previous efforts mapped spatial patterns and produced facies models of large microbial lacustrine systems, details of the origins of microbialite fabrics are less well constrained. To address these unknowns, this study evaluates the influence of organic matter source, abundance, and growth habit on Holocene microbialite fabrics. Integrated multi-scale analyses characterize fabrics of Holocene microbialites in a small, shallow, hypersaline, alkaline lake in the southern Bahamas. The results of analyses reveal: systematic distribution of surface sediment, unlithified microbial mats, and microbialites; microbialite fabrics vary considerably on several scales, and porosity varies from 43 to 59%; and organic matter abundance, rather than source, is interpreted to control fabric. Although ultimate preservation is unknown, understanding the genesis of primary fabrics may provide insights into pore evolution in reservoir analogs. Discovery of lacustrine microbialite reservoirs in South Atlantic pre-salt has motivated the search for analogs for perspectives on their deposition and initial porosity. Although previous efforts mapped spatial patterns and produced facies models of large microbial lacustrine systems, details of the origins of microbialite fabrics are less well constrained. To address these unknowns, this study evaluates the influence of organic matter source, abundance, and growth habit on Holocene microbialite fabrics. Integrated multi-scale analyses characterize fabrics of Holocene microbialites in a small, shallow, hypersaline, alkaline lake in the southern Bahamas. The results of analyses reveal: systematic distribution of surface sediment, unlithified microbial mats, and microbialites; microbialite fabrics vary considerably on several scales, and porosity varies from 43 to 59%; and organic matter abundance, rather than source, is interpreted to control fabric. Although ultimate preservation is unknown, understanding the genesis of primary fabrics may provide insights into pore evolution in reservoir analogs.