Academic literature on the topic 'Geology, history'

Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2002.<br>Web site works as of 02/10/03. Consult BYU Dept of Geology for URL changes in future. Includes bibliographical references (leaves 8-9). Also available via Internet.

Mountain building is the result of large compressional forces in the Earth’s crust where two tectonic plates collide. This is why mountains only form at plate boundaries, of which the Al Hajar Mountains in Oman and the United Arab Emirates is thought to be an example of. These mountains have formed near the Arabian–Eurasian convergent plate boundary where continental collision began by 30 Ma at the earliest. However, the time at which the Al Hajar Mountains developed is less well constrained. Therefore, the timing of both the growth of the mountains, and the Arabian–Eurasian collision, needs to be understood first to be able to identify a correlation. Following this a causal link can be determined. Here we show, using apatite fission track and apatite and zircon (U-Th)/He dating, as well as stratigraphic constraints, that the Al Hajar Mountains were uplifted from 45 Ma to 15 Ma. We found that the mountains developed 33 Myr to 10 Myr earlier than the Arabian–Eurasian plate collision. Furthermore, the plate collision is ongoing, but the Al Hajar Mountains are tectonically quiescent. Our results indicate that the uplift of the Al Hajar Mountains cannot be correlated in time to the Arabian–Eurasian collision. Therefore the Al Hajar Mountains are not the result of this converging plate boundary.

<p> Mohawk Valley is an inter montane basin with a rich Quaternary record, located at the northernmost end of the Sierra Nevada Mountains in northeastern California. Geologic mapping of surficial deposits, stratigraphy, tephrochronology, geomorphology, and soil development were used to interpret the past 740 ky of Quaternary history of Mohawk Valley. The robust tephrochronologic record within Mohawk Valley includes twenty-six different tephras and sixty-seven tephra beds that range in age from 740 to 7 ka. Geochemical analyses and correlations with previously identified volcanic tephras have resulted in revised age estimates for tephra beds distributed within, and beyond, Mohawk Valley. </p><p> The tephra beds were deposited in lacustrine deposits of Mohawk Lake. Elevations of shorelines and minimum lake-levels based on elevations of waterlain tephra beds were used to reconstruct the history of Mohawk Lake. Mohawk Lake began to fill prior to 740 ka and continued to fluctuate, but overall rise, until after 175-235 ka when the lake reached the sill elevation, began to spill to the west, then incrementally lower and empty by ~7 ka. Throughout this period, there were at least five, and up to nine, different generations of glacial deposits that extended towards Mohawk Lake. These glacial deposits have been mapped, their soil development and weathering properties characterized, and ages estimated based on stratigraphic relations with tephra beds deposited within Mohawk Lake deposits. This mostly continuous, 740 ky record of sedimentation has enormous potential to examine paleoclimate in this area from any of a number of paleoclimate proxies. </p><p> The interpretation that a deep lake existed in Mohawk Valley requires a mechanism to allow for deposition and preservation of organic-rich deposits in deep water. Mohawk Lake was likely a meromictic lake, a setting that leads to an anoxic environment that can preserve organic-rich sediments such as those found in Mohawk Valley. In addition, shorelines around Mohawk Valley and across much of the Mohawk Valley Fault Zone are at consistent elevations suggesting there is not a significant vertical component of faulting since 175-235 ka, and maybe since 570-610 ka. This indicates a change from the history of subsidence since the early Pliocene.</p>

Porcelain is a translucent vitreous material that consists of clay (kaolin), feldspar and quartz which has been mixed and heated together to cause a metamorphic reaction. In Sweden, the Porcelain industry was established in 1726 at Rörstrands castle in Stockholm and is today one of the oldest industries in Europe to produce porcelain. Around the 1790’s Rörstrand got its feldspars and quartz from the Ytterby mine that was located at Resarö in Stockholm’s archipelago making the raw material somewhat easy to access. Rörstrand owned the mine in the 1850’s to 1926. During the time Ytterby mine was active, an amateur geologist by the name of Carl Axel Arrhenius, discovered an unusual black mineral in the quarry ore in 1787 which later led to the discovery of 8 new rare earth elements (REE) with the help of several Swedish chemists throughout time. These elements are Yttrium, Ytterbium, Gadolinium, Terbium, Thulium, Erbium, Holmium and scandium. This study will focus on the Swedish porcelain industry and how it has evolved throughout history and Rörstrand’s role in the discovery of yttrium.