LAKE-BASIN-TYPES 2.0—EXPANDING THE MODEL TO THE 4TH DIMENSION… AND BEYOND!

The lake-basin-type model of Carroll and Bohacs (1999) classified the stratigraphic record of ancient lake systems according to rates of potential accommodation relative to sediment+water supply. To provide widespread applicability, the model convolved all modes and paths of water supply (direct fall, surficial, subsurface) with amounts and types of sediment supply (clastic, biogenic, chemical) into a single basin-filling volume term (sediment+water). Subsequent investigations confirmed the utility of this approach and widened its application beyond lake C cycles and resource evaluation to biological evolution and HC reservoirs, but also revealed some important limitations due to simplifications in the original model.

We propose adding two major subdivisions of the sediment+water term: 1) water-supply paths and 2) the volume of water supply relative to sediment supply.

Water-supply paths are categorized as ‘through-flow’ (for overfilled, balanced-fill, and underfilled lake-basin types), ‘recharge’ (for balanced-fill and underfilled), and ‘discharge’ (for underfilled) using Rosen’s 1994 approach. These paths can be deciphered using stable carbonate and oxygen isotope composition of primary lacustrine limestones, detailed sedimentology, and mineralogy. Distinguishing water-supply paths provides additional insights into playa systems and character of evaporite and carbonate strata.

The ratio of sediment and water volumes most directly influences the depth of lake waters which affect lake hydrodynamics and ecosystem behavior as well as the details of stratal stacking and depositional sequences. It helps fine-tune estimates of the distribution of porosity, permeability, and organic-matter content.

These additions can aid more detailed interpretations of lacustrine strata, understanding controls on biogeochemical cycles, and predicting the occurrence and distribution of various chemical species, but they are a hypothesis to be tested. The evolution of these lake models benefitted from being embraced by the limnogeology community (due to the work of such champions as Beth Gierlowki-Kordesch and her students). It showed the benefit of having relatively simple, but broadly applicable frameworks based on objective observations, to focus discussion and move a discipline forward.