Controls on grain‐size distribution in an ancient sand sea

Grain-size distribution in deserts is driven by a combination of autogenic controls such as grain abrasion and sorting due to wind transport, allogenic provenance spatial changes wind-direction. Downwind grain-size trends present day sand seas display contrasting results, with some showing broad downwind fining (for example, Namib Hexi) whilst others lack any clear trend Ténére, Australian Sinai). To determine the relative importance on seas, this study examines along margins Cretaceous Botucatu palaeodesert across an area >1 000 km2. quantify main distribution, compares metrics with: (i) detrital zircon geochronology test; (ii) palaeowind patterns wind-regime (iii) three transects basin palaeomargins test. dispersion shows east west pattern, which agrees control – contrast north–south expected for predominant control. In north-east region there good evidence aeolian about 0.4 μm kilometre, indicating that does occur, it limited rounded nature available possibly mix different sources. The results suggest primary sea potentially most large-scale dune fields.