Sedimentology of the Upper Cretaceous mammal- and dinosaur-bearing sites along the Râul Mare and Barbat rivers, Ha [formula omitted]eg Basin, Romania

Abstract

Mammal and dinosaur localities in the Ha t ̧ eg Basin belonging to the Upper Cretaceous Sânpetru and Densuş-Ciula formations have been known since the beginning of the last century. Recently, two new exposures with a comparable fauna have been discovered in the Râul Mare valley. The sediments at these new sites, Toteşti-baraj and Năla t ̧ -Vad, have been compared with the sediments at the previously known Pui site. At all three sites the deposits reflect a fluvial environment with coarse-grained channel deposits channelized in fine-grained floodplain deposits with calcrete palaeosols. However, the nature of the calcrete palaeosols is different at the three sites. At Toteşti-baraj and Năla t ̧ -Vad, hydromorphic calcic vertisols have been observed, and locally these grade into groundwater calcretes. At Pui, the calcretes are associated with redbed deposits. Considering the similar palaeogeographical situation and age of the deposits at the three sites, the difference in soil type should not be interpreted as a climatic difference but rather as a difference in the height of the palaeogroundwater table. The soils at Pui are indicative of a general semi-arid climate. Those at Toteşti-baraj and Năla t ̧ -Vad do not directly reflect the climate, but rather the high seasonal groundwater table. Differences in palaeohydrology between the sites are reflected in the fossil content with humidity-loving species only occurring at the Râul Mare sites.