901 resultados para Historical geology.
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The biogeography of the Glandulocaudinae ( former Glandulocaudini) is reviewed. The major pattern of diversification presented by this group of freshwater fishes can be clearly associated to the main aspects of the tectonic evolution of the southern portion of the Cis-Andean South American Platform. The phylogenetic relationships within the group suggest that the clade represented by Lophiobrycon is the sister-group of the more derived clade represented by the genus Glandulocauda and Mimagoniates. Lophiobrycon and Glandulocauda occur in areas of the ancient crystalline shield of southeastern Brazil and their present allopatric distribution is probably due to relict survival and tectonic vicariant events. Populations of Glandulocauda melanogenys are found in contiguous drainages in presently isolated upper parts of the Tiete, Guaratuba, Itatinga, and Ribeira de Iguape basins and this pattern of distribution is probably the result of river capture caused by tectonic processes that affected a large area in eastern and southeastern Brazil. The species of Mimagoniates are predominantly distributed along the eastern and southeastern coastal areas, but M. microlepis is additionally found in the rio Iguacu and Tibagi basins. Mimagoniates barberi occurs in both SW margin of the upper rio Parana basin and the lower Paraguay and Mimagoniates sp. occurs in the upper Paraguay river basin. Tectonic activations of the Continental Rift of Southeastern Brazil along the eastern margin of the Upper Parana basin promoted population fragmentation responsible of the present day distribution presented by Glandulocauda melanogenys. We hypothesize that occurrence of Mimagoniates along the lowland area around the Parana basin was due to a single or a multiple fragmentation of populations along the W-SW border of the upper Parana Basin, probably due to the major tectonic origin of the Chaco-Pantanal wetland foreland basins since the Miocene as well as Cenozoic tectonic activity along the borders of the upper Parana basin, such as in the eastern Paraguay, in the Asuncion Rift. Distributional pattern of Mimagoniates suggests that its initial diversification may be related to the tectonic evolution of the Chaco-Pantanal foreland basin system and a minimum age of 2.5 M.Y are proposed for this monophyletic group. Previous hypotheses on sea level fluctuations of the late Quaternary as being the main causal mechanism promoting cladogenesis and speciation of the group are critically reviewed. Phylogeographic studies based on molecular data indicate significant differences among the isolated populations of M. microlepis. These findings suggest that a much longer period of time and a paleogeographic landscape configuration of the Brazilian southeastern coastal region explain the present observed phylogenetic and biogeographic patterns.
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Mode of access: Internet.
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-pt.1. General geology. -pt.2. Historical geology.
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Part II has title: Geology manual; an instruction and laboratory manual in elementary geology.
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In this issue...Copper Lounge, Union Pacific Railway, Air Force, Circle K Club, Petroleum Engineers, Montana Power Company, Historical Geology Field Trip, Lime Spur Quarry
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Mode of access: Internet.
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Edited by Lydia Miller.
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Contains bibliographies.
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Added t.p., illustrated.
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In Thomas Mann’s tetralogy of the 1930s and 1940s, Joseph and His Brothers, the narrator declares history is not only “that which has happened and that which goes on happening in time,” but it is also “the stratified record upon which we set our feet, the ground beneath us.” By opening up history to its spatial, geographical, and geological dimensions Mann both predicts and encapsulates the twentieth-century’s “spatial turn,” a critical shift that divested geography of its largely passive role as history’s “stage” and brought to the fore intersections between the humanities and the earth sciences. In this paper, I draw out the relationships between history, narrative, geography, and geology revealed by this spatial turn and the questions these pose for thinking about the disciplinary relationship between geography and the humanities. As Mann’s statement exemplifies, the spatial turn itself has often been captured most strikingly in fiction, and I would argue nowhere more so than in Graham Swift’s Waterland (1983) and Anne Michaels’s Fugitive Pieces (1996), both of which present space, place, and landscape as having a palpable influence on history and memory. The geographical/geological line that runs through both Waterland and Fugitive Pieces continues through Tim Robinson’s non-fictional, two-volume “topographical” history Stones of Aran. Robinson’s Stones of Aran—which is not history, not geography, and not literature, and yet is all three—constructs an imaginative geography that renders inseparable geography, geology, history, memory, and the act of writing.
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Given the lack of proper constraints in understanding earthquake mechanisms in the cratonic interiors and the general absence of good quality database, here we reassess the seismic hazard in the province of Kerala, a part of the aEuro cent stable continental interioraEuro cent, based on an improved historical and instrumental database. The temporal pattern of the current seismicity suggests that > 60% of the microtremors in Kerala occurs with a time lag after the peak rainfall, indicating that hydroseismicity may be a plausible model to explain the low-level seismicity in this region. Further, an increment in overall seismicity rate in the region in the recent years is explained as due to increased anthropogenic activities, which includes changes in hydrological pathways as a consequence of rapid landscape changes. Our analyses of the historical database eliminate a few events that are ascribed to this region; this exercise has also led to identification of a few events, not previously noted. The improved historical database essentially suggests that the central midland region is more prone to seismic activity compared to other parts of Kerala. This region appears to have generated larger number of significant earthquakes; the most prominent being the multiple events (doublets) of 1856 and 1953, whose magnitudes are comparable to that of the 2000/2001 (central Kerala) events. Occurrences of these historical events and the recent earthquakes, and the local geology indicative of pervasive faulting as shown by widely distributed pseudotachylite veins suggest that the NNW-SSE trending faults in central midland Kerala may host discrete potentially active sources that may be capable of generating light to moderate size earthquakes. The frequency of earthquakes in central Kerala evident from the historical database requires that the seismic codes stipulated for this region are made mandatory.
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From the 1940s until 2003, portions of the island of Vieques, a municipality within the Commonwealth of Puerto Rico, were used by the US Navy as a base and training facility, resulting in development and zoning history that differ in comparison to other Caribbean islands. The majority of former Navy lands are now under the jurisdiction of the Department of the Interior’s Fish and Wildlife Service as a National Wildlife Refuge, while a smaller percentage of land was transferred to the Vieques municipality and the Puerto Rico Conservation Trust. An analysis of the distribution and status of the marine resources is timely in light of the recent land transfer, increases in development and tourism, and potential changes in marine zoning around the island. To meet this need, NOAA’s Biogeography Branch, in cooperation with the Office of Response and Restoration and other local and regional partners, conducted Part I of an ecological characterization to integrate historical data and research into a synthesis report. The overall objective of this report is to provide resource managers and residents a comprehensive characterization of the marine resources of Vieques to support research, monitoring, and management. For example, knowledge of the spatial distribution of physical features, habitats, and biological communities is necessary to make an informed decision of the establishment and placement of a marine protected area (MPA). The report is divided into chapters based on the physical environment (e.g., climate, geology, bathymetry), habitat types (e.g., reefs and hardbottom, seagrasses, mangroves) and major faunal groups (e.g. fish, turtles, birds). Each section includes five subsections: an overview, description of the relevant literature, methods of analysis, information on the distribution, status and trends of the particular resource, and a discussion of ecological linkages with other components of the Vieques marine ecosystem and surrounding environment. The physical environment of Vieques is similar to other islands within the Greater Antilles chain, with some distinctions. The warm, tropical climate of Vieques, mediated by the northeasterly trade winds, is characterized by a dry season (December-April) and a rainy season (May-November), the latter of which is characterized by the occasional passage of tropical cyclones. Compared to mainland Puerto Rico, Vieques is characterized by lower elevation, less annual precipitation, and higher average temperatures. The amount of annual precipitation also varies spatially within Vieques, with the western portion of the island receiving higher amounts of rainfall than further east. While the North Equatorial Current dominates the circulation pattern in the Greater Antilles region, small scale current patterns specific to Vieques are not as well characterized. These physical processes are important factors mitigating the distribution and composition of marine benthic habitats around Vieques. In general, the topography of Vieques is characterized by rolling hills. Mt. Pirata, the tallest point at 301 m, is located near the southwest coast. In the absence of island wide sedimentation measurements, information on land cover, slope, precipitation, and soil type were used to estimate relative erosion potential and sediment delivery for each watershed. While slope and precipitation amount are the primary driving factors controlling runoff, land use practices such as urban development, military activity, road construction, and agriculture can increase the delivery of pollution and sediments to coastal waters. Due to the recent land transfer, increased development and tourism is expected, which may result in changes in the input of sediments to the coastal environment.