This work broadly impacts our knowledge of how low latitude terrestrial environments responded to major climatic shifts. Large and abrupt changes in the high-resolution strontium isotope record mirror changes in the percentage and flux of terrigenous material at the site. Petrography and trace element analysis are important components of understanding what samples are the best candidates for accurate and precise dating, and were a focus of much of this research. Tufas are exposed on a ridge southwest of Owl Canyon Campground. We have used this technique to aid in sample selection for U-Pb dating and synchrotron X-radiation studies. Sample is composed of brown laminated calcite framework, dark green and red sparry calcite, and translucent white chalcedony.
Neodymium isotopes remain essentially constant over the record, suggesting that general geologic provenance has not appreciably changed. This locality is 260 m below the Skyline Tuff and is marked with a star. Right panel: The section between Owl and Solomon Canyons is the lithostratigraphic type section for the Barstow Formation and was measured on the north limb of the Barstow syncline (Durrell, 1953).
Three black fragments (a, b, c) were analysed with a scanning electron microscope energy dispersive spectrometry probe (SEM–EDS) (e, f), fast Fourier infra-red, FTIR (d) and Raman spectrometry (g, h, i).
FTIR analyses were made at the Laboratoire de Physique des Solides (LPS), Paris-XI University, Orsay by S. Raman spectroscopy was performed with an Invia spectrometer from Renishaw and the atomic spectrometry was performed with a FE-SEM Zeiss Sigma equipped with an EDS probe at the École Normale Supérieure, Paris, France.
a, A 6.7-cm-long piece of burnt bone (Br-SE-Os) trapped between stalagmite elements in structure E (Extended Data Fig.
The bone with the 5-mm-thick calcite crust was cut longitudinally and the calcite was sampled along deposition layers, starting at the internal surface after removing the bone material.
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I am also interested in applying U-Pb to date Quaternary sedimentary calcite.
The position of the phytoherm tufa locality on the north limb of the syncline is estimated on this section with a star.