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Geological Evolution (geological + evolution)

Distribution by Scientific Domains

Earth and Environmental Science	80%

Selected Abstracts

Geological evolution and structural style of the Palaeozoic Tafilalt sub-basin, eastern Anti-Atlas (Morocco, North Africa)

GEOLOGICAL JOURNAL, Issue 1 2008
E. A. Toto
Abstract The Tafilalt is one of a number of generally unexplored sub-basins in the eastern Anti-Atlas of Morocco, all of which probably underwent a similar tectono-stratigraphic evolution during the Palaeozoic Era. Analysis of over 1000,km of 2-D seismic reflection profiles, with the interpretation of ten regional seismic sections and five isopach and isobath maps, suggests a multi-phase deformation history for the Palaeozoic-aged Tafilalt sub-basins. Extensional phases were probably initiated in the Cambrian, followed by uniform thermal subsidence up to at least the end of the Silurian. Major extension and subsidence did not begin prior to Middle/Upper Devonian times. Extensional movements on the major faults bounding the basin to the north and to the south took place in synchronisation with Upper Devonian sedimentation, which provides the thickest part of the sedimentary sequence in the basin. The onset of the compressional phase in Carboniferous times is indicated by reflectors in the Carboniferous sequence progressively onlapping onto the Upper Devonian sequence. This period of compression developed folds and faults in the Upper Palaeozoic-aged strata, producing a structural style characteristic of thin-skinned fold and thrust belts. The Late Palaeozoic units are detached over a regional décollement with a northward tectonic vergence. The folds have been formed by the process of fault-propagation folding related to the thrust imbricates that ramp up-section from the décollement. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Stratabound Rayleigh convection observed in a 4D hydrothermal reactive transport model based on the regional geological evolution of Allermöhe (Germany)

GEOFLUIDS (ELECTRONIC), Issue 3 2007
M. KÜHN
Abstract We investigated stratabound Rayleigh convection as a means of transport for leaching of solutes from salt diapirs, their dissipation into the Rhaetian sandstone aquifer and subsequent precipitation of anhydrite with resulting cementation. Reactive transport modelling has been conducted in the context of the recent structure of the Allermöhe site and its palaeogeological development. Resulting flow fields depict large (km-scale) stratabound Rayleigh convection. However, our simulations show the vicinity of the Allermöhe well as a potential area of anhydrite dissolution in contrast to field observations, with precipitation concentrated elsewhere. [source]

Baguio Mineral District: An oceanic arc witness to the geological evolution of northern Luzon, Philippines

ISLAND ARC, Issue 4 2008
Graciano P. Yumul Jr
Abstract The Baguio Mineral District exposes rock formations that evince the geological and tectonic evolution of this district from a subduction-related marginal basin to an island arc setting. Available onshore and offshore data are consistent with an Early (onset phase) to Middle (developed phase) Miocene arc polarity reversal from the east (termination of subduction along the proto-East Luzon Trough) to the west (initiation of subduction along the Manila Trench). Geophysical modeling and geochemical data calculation showed a 30 ± 5 km crustal thickness for the mineral district. Subduction-related multiple arc magmatism and ophiolite accretion contributed to crustal thickening. Recent information on the Oligo,Miocene Zigzag and Klondyke formations in the mineral district reveal that the marginal basin, where these rocks were deposited, has received eroded materials from adjacent terrains characterized by siliceous lithologies. Furthermore, adakitic rocks, high permeable zones and extensional zones which are exploration markers applied to identify possible mineralization targets, are prevalent in the mineral district. The geological evolution that the district had undergone mimics the evolution of island arcs worldwide in general and northern Luzon in particular. [source]

Phylogenetic relationships, diversification and biogeography in Neotropical Brotogeris parakeets

JOURNAL OF BIOGEOGRAPHY, Issue 9 2009
Camila C. Ribas
Abstract Aim, We present a molecular phylogenetic analysis of Brotogeris (Psittacidae) using several distinct and complementary approaches: we test the monophyly of the genus, delineate the basal taxa within it, uncover their phylogenetic relationships, and finally, based on these results, we perform temporal and spatial comparative analyses to help elucidate the historical biogeography of the Neotropical region. Location, Neotropical lowlands, including dry and humid forests. Methods, Phylogenetic relationships within Brotogeris were investigated using the complete sequences of the mitochondrial genes cyt b and ND2, and partial sequences of the nuclear intron 7 of the gene for Beta Fibrinogen for all eight species and 12 of the 17 taxa recognized within the genus (total of 63 individuals). In order to delinetae the basal taxa within the genus we used both molecular and plumage variation, the latter being based on the examination of 597 skin specimens. Dates of divergence and confidence intervals were estimated using penalized likelihood. Spatial and temporal comparative analyses were performed including several closely related parrot genera. Results,Brotogeris was found to be a monophyletic genus, sister to Myiopsitta. The phylogenetic analyses recovered eight well-supported clades representing the recognized biological species. Although some described subspecies are diagnosably distinct based on morphology, there was generally little intraspecific mtDNA variation. The Amazonian species had different phylogenetic affinities and did not group in a monophyletic clade. Brotogeris diversification took place during the last 6 Myr, the same time-frame as previously found for Pionus and Pyrilia. Main conclusions, The biogeographical history of Brotogeris implies a dynamic history for South American biomes since the Pliocene. It corroborates the idea that the geological evolution of Amazonia has been important in shaping its biodiversity, argues against the idea that the region has been environmentally stable during the Quaternary, and suggests dynamic interactions between wet and dry forest habitats in South America, with representatives of the Amazonian biota having several independent close relationships with taxa endemic to other biomes. [source]

Detrital Zircon of 4100 Ma in Quartzite in Burang, Tibet

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 6 2006
DUO Ji
Abstract: A detrital zircon aged 4.1 Ga is discovered by the SHRIMP U-Pb method in a quartzite in Burang County, western Tibet. This is presently the oldest single-grain detrital zircon in China. The Th-U ratios of the two testing points of the >4.0 Ga zircon are between 0.76 and 0.86, indicating their magmatic origin. This discovery has offered an important age for investigating the geological evolution of the Qinghai-Tibet Plateau. [source]