Filters: Tags: {"scheme":"Geographic Names Index System (GNIS) place names (https://geonames.usgs.gov/apex/f?p (X)
3 results (12ms)
Filters
Date Range
Contacts
Categories Tag Types Tags (with Scheme=Geographic Names Index System (GNIS) place names (https://geonames.usgs.gov/apex/f?p=138:1:0:::::)) |
Temporal and spatial sources of silica for chert remain poorly constrained. Modern sources to the worlds oceans include silica in rivers > aeolian (dust) deposition > sea floor vents and submarine weathering. However, changes in aridity and dust flux during the Phanerozoic may explain variations in the ocean silica cycle and times and places of chert formation. The chemistry of fine quartz dust (FQD) provides a chemical mechanism for the transformation of FQD to polymorphs of silica in chert; FQD is readily dissolved, then reprecipitated as Opal-A by either biotic or abiotic processes. An unequivocal relation between increases in dust flux and biogenic opal-A in the western Pacific Ocean during the past 200 kyr...
This data release contains 60 detrital zircon age spectra, based on U and Pb isotope ratio measurements for 9399 single grains. The samples are from Paleogene strata of the U.S. Gulf Coast. Of the 9399 single grain measurements, we recommend that 8640 yield ages that are suitable for construction of detrital zircon age spectra. Comments tagged to individual grains explain the reasoning for exclusion of a single grain measurement from age spectra, mostly including high discordance and/or uncertainty. The samples were collected along the strike of the U.S. Gulf Coast basin between western Alabama (the eastern U.S. Gulf Coast) and the Rio Grande river (the southwestern boundary of the U.S. Gulf Coast). The highest...
Raman spectroscopy was studied as a thermal maturity probe in a series of Upper Devonian Ohio Shale samples from the Appalachian Basin spanning from immature to dry gas conditions. Raman spectroscopy also was applied to samples spanning a similar thermal range created from 72-hour hydrous pyrolysis (HP) experiments of the Ohio Shale at temperatures from 300 to 360°C and isothermal HP experiments lasting up to 100 days of similar Devonian-Mississippian New Albany Shale. Raman spectra were treated by an automated evaluation software based on iterative and simultaneous modeling of signal and baseline functions to decrease subjectivity. Spectra show robust correlation to measured solid bitumen reflectance (BRo) values...
|
|