Authigenic, volcanogenic, and detrital influences on the Cenomanian–Turonian clay sedimentation in the Western Interior Basin: Implications for palaeoclimatic reconstructions

Abstract

High-resolution changes in the mineralogical assemblages at Pueblo and Hot Springs of the Western Interior Basin (WIB, USA) were investigated for the late Cenomanian–early Turonian interval, including the Oceanic Anoxic Event 2 (OAE2). The aim of this study is to investigate the regional significance of clay mineral assemblages in the WIB by distinguishing authigenic, volcanogenic, and detrital influences. At Pueblo, the last few centimetres of the Hartland Shale and the Bridge Creek Limestone formations present an abrupt increase in R0 I–S content (up to 90% of the clay signal), which is coeval to an important incursion of subtropical Pacific seawater entered in the seaway from the Gulf of Mexico. We suggest that sea-level changes and volcanic activity expressed by bentonite horizons constitute the principal source of smectitic minerals found in the south central region of the basin. At equivalent stratigraphic interval in the Hot Springs section, situated 5° north of Pueblo (∼600 km north), the smectitic sedimentation was mixed by local detrital input in kaolinite (from 6 to 45%). The great abundance of detrital kaolinite at the northern Hot Springs site is probably due to a very different clay provenance in that part of the seaway. It appears that two local supplies of kaolinite are recorded in the S. gracile ammonite zone (up to 45%) and in the latest Cenomanian–early Turonian interval (from 6 to 31%). The particular geographic configuration of the Western Interior Basin (arrangement of landmasses and the seaway) in the tropical-subtropical environment initiate and maintain seasonally reversing movements of air mass, high evaporation flux, atmospheric heat transport, and precipitation. In this regards, we suggest that local kaolinite input reflect a more humid climate can be attributed to the local intensity of monsoonal-driven precipitation.