Search results
Results from the WOW.Com Content Network
The Neoproterozoic Nankoweap Formation (pronounced Nan' coe weep), is a thin sequence of distinctive red beds that consist of reddish brown and tan sandstones and subordinate siltstones and mudrocks that unconformably overlie basaltic lava flows of the Cardenas Basalt of the Unkar Group and underlie the sedimentary strata of the Galeros Formation of the Chuar Group.
Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars.
The estimated depositional age of the Dresser Formation is inferred to be between 3483 and 3479 Ma. It is older than the ~3470 Ma Mount Ada Basalt and younger than the ~3490 Ma North Star Basalt. [1] [13] Syngenetic galena from barite in the Dresser Formation was dated at about ~3490 Ma. [14]
The Ashangi Basalts are the earliest Tertiary volcanic rocks in north Ethiopia, hence they are in the lowest position.These dark porphyritic basalts are separated from the Mesozoic formations below it by basal conglomerates.
Apparently, fluids associated with the deposition of the Chuar Group have altered the older Cardenas Basalt, partially degraded the minerals, and therefore producing a disruption in the K-Ar systematics. Using newer dating techniques and approaches not available to earlier geologists, the Cardenas Basalt and intrusive sills have been re-dated.
The current interpretation is that the deposition of the overlying Chuar Group in a marine setting disrupted the potassium-argon (K-Ar) radiometric system. Apparently, fluids associated with the deposition of the Chuar Group have altered the older Cardenas Basalt, partially degraded the minerals, and therefore disrupted the K-Ar systematics.
The change from Bass Formation to the lower member likely represent the waning stages of marine deposition during which the Bass Formation accumulated. The Cheops Pyramid (middle) member is regarded to have accumulated either in a shallow, near-shore marine environment or in coastal plain mudflats, or deltas. The greenish gray reduction mottles ...
A diagram of various depositional environments. In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record.