Miocene-Pleistocene Paleoclimate and Paleoenvironment in the Meade Basin, Kansas

Abstract:

The Meade Basin in southwestern Kansas preserves a unique record of paleovegetation and small mammal faunal change from the Miocene to the Pleistocene. Many of the paleosols preserved in this basin contain paleosol carbonate nodules, thick calcretes and abundant organic-rich horizons, which makes it ideally suited for a multiproxy study that explores the role of paleoenvironmental change in driving floral and faunal change. Here we focus on the carbonate samples where we measured carbon and oxygen isotopes (δ¹³C_c and δ¹⁸O_c, respectively); used clumped isotope thermometry (Δ₄₇) to estimate soil temperature and soil water δ¹⁸O; and assessed the preservation state and additional paleoenvironmental features of the samples using optical and cathodoluminescence (CL) microscopy.

The carbon isotope record matches previous studies from the region and shows an increase in the relative abundance of C₄ biomass on the landscape since the late Miocene. The Δ₄₇ temperatures and the δ¹⁸O of soil water, while variable, show no significant change in average values through time. The textural and luminescenece characteristics suggest some samples have undergone moderate to extensive diagenetic alteration from groundwater fluids, perhaps causing some of the variability in the geochemical records. Soil depth may also account for some of the variability. Overall, these data suggest that temperature is unlikely to be the dominant factor driving paleovegetation and faunal change in this region from the Miocene to Pleistocene. In addition, these data highlight the importance of assessing preservation for all carbonate samples, regardless of whether or not the samples have been deeply buried.