The Turonian-Coniacian deposits of the south-west of the Ulyanovsk-Saratov trough

Abstract

Integrated study of a series of the Turonian and Coniacian complete geological records has revealed the stratigraphic completeness and specified the faunal contents of the deposits. The south and the southwest of the Ulyanovsk-Saratov trough have been shown to comprise the thickest beds of the studied interval represented by carbonate and carbonate-terrigenous rocks. Northwards, in the zone of the Saratov dislocations, the Turonian – Coniacian bodies are peculiar for terrigenous and terrigenous-carbonate compositions. The beds are ubiquitously monotonous, which complicates identifications at the stage and the substage levels. Distributions of the benthic foraminifer assemblages and the data on the finds of cephalopods, inoceramus, echinoderms, brachiopods and siliceous sponges have allowed to distinguish detailed biostratigraphic units at the level of biozones traced within the examined structural units. An attempt has been made to reconstruct the conditions in the marine environment.

Keywords

• турон
• коньяк
• ульяновско-саратовский прогиб
• аммониты
• белемниты
• иноцерамы
• бентосные фораминиферы
• иглокожие
• брахиоподы
• кремниевые губки