Closed Basin Hypsometric Curves Influence on Lacustrine Stratigraphy

Abstract

Lake basins are well known to have significant accumulations of organic rich sediments and prolific hydrocarbon provinces with high total organic carbon (TOC) source rocks. The lake basins have been recognized to have a different sequence stratigraphy dynamics (water and sediment fluxes are in phase) when compare with the marine basins. One widely used classification of lake basins stratigraphy separated under-fill, balance-fill and over-fill type basins.

This study is based on a numerical model which is using the closed basin hypsometric curves and climatic conditions (precipitation, evaporation) to explore the lake levels and water/ sediment fluxes dynamics. The hypsometric curves have different shapes according to the basin origin (rift, glacial, sag) and that controls the water level and sediment fluxes in each type of basin. However, there are some commonalities in that they have a relative low gradient bottom (hypsometric curve is flat at low elevation), and that overspill is not at the top of the hypsometric curve. The results indicate that low lake level is more sensible to the climate changes that the high lake level and as a consequence of this the regression-transgression cycles have longer migration distances and migration rates at low lake levels. The modeling results are compared with published data from modern large lakes and their most recent known evolution of the water level.

Because the clastic sediment flux is in phase with water flux to the basin, a model for lake depocenters linked to the hypsometric curve is proposed in which the fate of continental organic derived detritus or lake produced organic matter is also discussed. The proposed model is not targeting a specific lake basin to explain the preserved/ observed stratigraphy but is intended to show the range of possible siliciclastic depocenter migration scenarios according to the hypsometric curve distribution. The model explain the observed and inferred abrupt changes in depositional environments that usually are not well understood but otherwise seems to be common occurrences and one of the key peculiarities of the lake basins stratigraphy.

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