Sedimentation and diagenesis during the late Paleozoic Ice Age: Arrow Canyon, Nevada and the Capitan backreef, Slaughter Canyon, New Mexico

The late Paleozoic Ice Age (LPIA) was the longest-lived, most expansive ice age of the past 0.5 Ga. During this time, carbonate deposition was widespread across North America, which lay in the tropics. This dissertation focuses on two late Paleozoic carbonate platforms (the Capitan backreef, NM, and the Bird Spring ramp, NV) and highlights the complex climatic and diagenetic signatures preserved in strata of this age.;Carbonate strata in Arrow Canyon preserve evidence for dynamic climate change during the Carboniferous. These strata indicate a Middle Mississippian onset for the LPIA, followed by high-amplitude sea-level fluctuations. High-amplitude glacio-eustasy was punctuated by two glacial minima: a short-lived minimum during the earliest Pennsylvanian, and a long-lived minimum during the Late Pennsylvanian. Transitions between climate states are indicated by changes in the types of m-scale cycles, their constituent facies, bounding surfaces, and climate indicators. Of particular note, Middle Pennsylvanian icehouse strata include ikaite pseudomorphs, which indicate near-freezing, shallow subtidal waters at the equator. These findings are consistent with the high-latitude record of glaciogenic sedimentation and denote a Carboniferous tropical climate much more dynamic than previously assumed.;The middle Permian Capitan backreef was deposited at the close of the LPIA. This study examines delta13C and delta18O values from various components in one m-scale cycle, measured in 4 parallel sections in Slaughter Canyon. delta13C and delta 18O analyses delineate an "inverted J-curve", diagnostic of fluid-rock interaction. Blocky calcite spars precipitated from fluid-buffered pore waters. These waters also variably reset isotopic values in marine cements, matrix, and bulk carbonate, destroying primary stratigraphic trends. Combined isotopic and petrographic characteristics suggest isotopic resetting was due to neither simple meteoric nor burial diagenesis. Additionally, these results suggest that micritic matrix was more susceptible to alteration than marine cement, and that traditional diagenetic screening methods are inadequate. In the Capitan backreef, significant isotopic variability (2-4‰ in both delta 13C and delta18O) exists in samples that are texturally well preserved and low in Fe and Mn. These results suggest that careful diagenetic screening and component isotopic analyses in multiple parallel sections may be required to avert erroneous interpretations of chemostratigraphic curves.