<p>Deciphering records of deep-time sea level, climate, and oceanographic variation from drowned carbonate platforms is useful, including perhaps to help predict risk of drowning on modern platforms experiencing anthropogenic sea-level rise. However, prediction is complicated by incomplete understanding of how observed platform geometries record different drowning processes. Here we analyze seismic-scale numerical stratigraphic forward model results that suggest backstepping drowning geometries occur when platform-top sediment transport redistributes sediment and drives complex autogenic production-transport feedbacks that help maintain a broad shallow-water platform-top area. In contrast, without sufficient sediment transport on platforms dominated by in-situ production, pinnacle drowning geometries tend to be produced. These results suggest platform drowning geometries represent a complex mix of controlling processes that, with careful interpretation, could provide robust information about deep-time climate and sea-level change, and may also help predict evolution of modern platforms responding to rising global sea level.</p>