Abstract

We investigated the Mayrán Formation (late Neogene), exposed in northeast México, to determine the ways in which antecedenttopography, climate, sediment input, bedrock geology, and primary production controlled facies architectures in this lacustrine-dominated succession. The succession was deposited in four, broadly coeval lake subbasins (Mayrán Basin system) developed at different elevations. The subbasins are separated by Cretaceous bedrock ridges and infilled by differing proportions of siliciclastic and carbonate deposits. Adjacent subbasins are connected by spillover points. To investigate how these factors controlled overall facies architectures, we generated a structural and stratigraphic framework for each subbasin. In the most proximal subbasin (I), alluvial sediments consisting of nonchannelized and channelized conglomerates, pebblysandstones, and calcareous sandy and siliciclastic mudstones change laterally into horizontally bedded lacustrine limestones, calcareous mudstones, and evaporites. Vertically, these lithofacies are organized into shallowing-upward cycles. The more distal subbasins (II–IV) are predominantly filled by lacustrine limestones. Striking aggradational and progradational tufa topsets and clinoforms are present at the spillover points (waterfalls) between subbasins. These tufas interfinger up- and downdip with the lacustrine limestones.

The distribution of clastic facies was mainly controlled by their proximity to the major sediment input in the south, and to the Cretaceous bedrock ridges. Primary production within each subbasin was controlled by a combination of lake level, accommodation availability, and solute inputs. Overall, while autogenic processes likely controlled facies distribution within the basin, climate was the overall driver of large-scale facies variability.

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