Search results for "Peneplain"
showing 3 items of 3 documents
Tertiary maars of the Hocheifel Volcanic Field, Germany
2008
In the Hocheifel only three maars are known. The Eckfeld Maar, filled with Eocene lacustrine sediments, is located at the southern boundary of the volcanic field, where the Tertiary peneplain has been eroded only slightly. The ages of the Jungferweiher Maar in the southeast and the Dottingen Maar in the northeast of the Tertiary Hocheifel Volcanic Field (THVF) are unknown and their timing within the THVF is uncertain. In contrast to the surrounding area, the central part of the THVF is deeply eroded. Here, six large diatremes (>600 m) were identified in the area of Kelberg with one exception. So far, no relics of crater sediments have been found within the large diatremes. They probably rep…
Carbon isotope geochemistry and geochronological constraints of the Neoproterozoic Sirohi Group from northwest India
2012
a b s t r a c t The early Neoproterozoic carbonates of the Sirohi Group, northwestern India, were studied for geochronology as well as for oxygen and carbon isotopes across three different sections to understand their relationship with contemporaneous global events. New single zircon Pb-Pb evaporation data con- strain the age of the Sirohi Group between ca. 920 and ca. 820 Ma, though actual span for deposition of the carbonates may be little shorter taking into allowance the time for peneplanation. Narrow range in variation of 18O values is generally observed in the carbonate which is consistent with generally well-preserved original compositions. Two sections (SA and SS) out of the three t…
Age and mineralogy of supergene uranium minerals — Tools to unravel geomorphological and palaeohydrological processes in granitic terrains (Bohemian …
2010
Abstract Uranyl phosphates (torbernite, autunite, uranocircite, saleeite) and hydrated uranyl silicates (normal and beta-uranophane) found in various erosion levels and structures in the Late Variscan granites at the western edge of the Bohemian Massif, Germany, were the target of mineralogical investigations and age dating, using conventional and more advanced techniques such as Laser-Ablation-Inductive-Coupled-Plasma Mass Spectrometry (LA-ICP-MS). Supergene U minerals have an edge over other rock-forming minerals for such studies, because of their inherent ‘clock’ and their swift response to chemical and physical environmental changes on different scales. Uraniferous phoscretes and silcre…