Showing papers by "Jay L. Banner published in 2000"
Journal Article•
TL;DR: In this paper, the authors present a set of high-resolution, seawater Sr and C isotope curves for the late Early through early Late Cambrian, defined in continuous exposures of marine carbonates in the Great Basin and southern Canadian Rockies, and used to better constrain primary variations in ocean chemistry during this time period.
Abstract: The recent proliferation of chemostratigraphic studies has clearly documented that systematic fluctuations in the strontium and carbon isotope composition of seawater have occurred throughout Earth history across a range of temporal scales. In particular, significant isotopic variation during key intervals of geologic time has provided unprecedented quantitative constraints on crustal and surficial processes, and enhanced chronostratigraphic resolution for intrabasinal and interbasinal correlations. We present the first set of high-resolution, seawater Sr and C isotope curves for the late Early through early Late Cambrian. These curves are defined in continuous exposures of marine carbonates in the Great Basin and southern Canadian Rockies, and they are used to better constrain primary variations in ocean chemistry during this time period. The Sr curve documents a rapid rate of increase through this period that is comparable to that recorded by the late Cenozoic seawater Sr proxy record of uplift and attendant weathering of the HimalayaTibetan Plateau. The Cambrian rise in Sr values is interpreted to record PanAfrican‐Brasiliano orogenesis, and
477 citations
TL;DR: In this article, seasonal and spatial variations in recharge to the Pleistocene limestone aquifer of Barbados are obtained from the analysis of oxygen isotopic compositions of groundwater and rainwater.
Abstract: Unique constraints on seasonal and spatial variations in recharge to the Pleistocene limestone aquifer of Barbados are obtained from the analysis of oxygen isotopic compositions of groundwater and rainwater. Conventional methods of estimating recharge are based on groundwater chloride variations, coastal groundwater discharge, and potential evapotranspiration. These methods typically yield estimates of recharge for Barbados that range from 9% to 20% of average annual rainfall, with significant uncertainties that arise from poorly constrained model input parameters. Owing to the low relief and tropical climate of Barbados, variations in rainwater and groundwater δ18O values are primarily influenced by the amount of rainfall, with negligible temperature or altitude effects. Composite monthly rainwater δ18O values are inversely related to rainfall, while groundwater δ18O values show little seasonal variability. Rainwater δ18O values are equivalent to groundwater values only at the peak of the wet season. By using mass balance, the difference between groundwater and weighted-mean rainwater δ18O values gives recharge values. These values are in general agreement with estimates by conventional methods (10–20%) and provide unique additional information including the following: (1) Recharge is restricted to the wettest 1–3 months of the year, and (2) there is less recharge at higher elevations. The effective shift in δ18O values between contemporaneous rainwater and groundwater via recharge is a useful tool for estimating temporal and spatial variability in recharge and must be considered in paleoclimatic studies where climate inferences are based on groundwater δ18O values preserved in the geologic record.
95 citations
TL;DR: An extensive saline plume within the regionally important unconfined aquifer in the Neogene Ogallala Formation overlies the Panhandle oil and gas field in the Southern High Plains, Texas, USA as discussed by the authors.
58 citations