Continental paleoclimate estimates from the late Mississippian Redwall karst event: northern and north-central Arizona (USA)

Abstract

The Redwall Limestone of northern and north-central Arizona (USA) was investigated to determine if suitable secondary silica precipitates were present and which could be used to estimate continental weathering temperatures for the late Carboniferous period. Secondary (authigenic) silica precipitates in lag deposits of chert and residual rubble breccia of oxidized and durable earth material under subaerial weathering during karst events. The Redwall Limestone was extensively karsted for millions of years during the late Carboniferous and suitable secondary silica precipitates were collected from chert lag deposits and residual breccias for isotopic analyses. The stable isotopic (oxygen and deuterium) composition of secondary silica has been successfully used by the author on samples as old as the late Proterozoic to estimate continental paleotemperatures. Isotopic data from secondary silica precipitated during the tropical karst event developed on the Mississippian Redwall Limestone indicate that continental weathering temperatures during the late Carboniferous ranged from ~21–34°C.