Modern muds of Laguna Mar Chiquita (Argentina): Particle size and organic matter geochemical trends from a large saline lake in the thick-skinned Andean foreland

Laguna Mar Chiquita (central Argentina; ~latitude 31°S, longitude 63°W) provides an outstanding opportunity to examine organic facies development and petroleum source-rock potential in a modern thick-skinned foreland basin lake. In this case study, we defi ne profundal, paleodelta, and lake-margin depositional environments based on trends in bathymetry and lake-fl oor sediment particle size. Sedimentary geochemical analyses indicate that organic carbon–rich muds accumulate in profundal environments during the extant lake-level highstand. The lateral variability of organic facies is minimal. The quality of organic facies is controlled by lake level and depositional environment, both of which dictate patterns of algal productivity, siliciclastic dilution, and early diagenesis. We present conceptual models of lacustrine source rocks in both thick-skinned and thin-skinned foreland basins based on modern analog data from both Laguna Mar Chiquita and other lakes in the central Andean foreland. Over relatively short time intervals (102–104 yr), climatically driven water-level fl uctuations infl uence the source-rock potential of these basins. Over time intervals >105 yr, contraction and lateral migration of the basin fl exural profi le control stratal stacking patterns and the potential for hydrocarbon play development. *[email protected] McGlue, M.M., Ellis, G.S., and Cohen, A.S., 2015, Modern muds of Laguna Mar Chiquita (Argentina): Particle size and organic matter geochemical trends from a large saline lake in the thick-skinned Andean foreland, in Larsen, D., Egenhoff, S.O., and Fishman, N.S., eds., Paying Attention to Mudrocks: Priceless!: Geological Society of America Special Paper 515, p. 1–18, doi:10.1130/2015.2515(01). For permission to copy, contact [email protected]. © 2015 The Geological Society of America. All rights reserved. on August 18, 2015 specialpapers.gsapubs.org Downloaded from