Precambrian quartzo-feldspathic gneiss was encountered at an elevation of —3616 feet in the Herman 1A well drilled in southeastern Erie County, Ohio, by the Amerada Petroleum Corporation. The five samples of this gneiss that were studied exhibit varying degrees of gneissose foliation. In order of decreasing abundance, microcline, plagioclase, quartz, and biotite together account for an average ...

The assumptions of conventional whole-rock and mineral isochron radioisotope dating were tested using a suite of radioisotopes from two Precambrian rocks. Amphibolite from the Beartooth Mountains of Wyoming shows evidence of thorough metamorphism by isochemical processes from andesite by an early Precambrian magma-intrusion event. A diabase sill, exposed within the wall of Grand Canyon at Bass ...

Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1....

The semidiurnal atmospheric thermal tide would have been resonant with free oscillations of the atmosphere when the day was approximately 21 h long, c. 600 Ma ago. Very large atmospheric tides would have resulted, with associated surface pressure oscillations in excess of 10 mbar in the tropics. Near resonance the Sun's gravitational torque on the atmospheric tide--accelerating Earth's rotati...