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Cascading process systems
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Zones of spreading are associated with rift belts predominantly in mid-oceanic locations (see Chapter 5). These zones are characterized by uplift and the moving apart of rift boundaries, relative subsidence of the central graben and volcanic activity. Rates of spreading vary from a low of 10 mm per year in the Norwegian Sea to a maximum of 183 mm per year in parts of the East Pacific Rise. Projecting this latter rate backwards in time, it is possible that the whole floor of the Eastern Pacific could have been generated in little more than 130 million years (see Figure 5.13), although as Table 5.4 shows rates of spreading are very variable in time, for example, that of the Mid-Atlantic Ridge decreasing from an average of 20 mm per year in the Early Eocene to less than one-half this figure in the Late Eocene. In Iceland contemporary rates of rift-widening differ from place to place with maxima ranging from 7 to 23 mm per year. The graben floor in north Iceland is subsiding at 4–7 mm per year, whereas the floor of the Ethiopian Rift Valley is subsiding at about 12 mm per year with the adjacent Somaliland coast rising at some 2 mm per year between 1935 and 1960.
Morphotectonic indications for the opening of Davis Strait
Published in Hans-Peter Rossmanith, Mechanics of Jointed and Faulted Rock, 2018
Davis Strait is the body of water that separates the southern parts of Greenland and those of Baffin Island (Fig. 1); it connects Baffin Bay with the Labrador Sea. Its origin is generally assumed to be the result of an initial rift and subsequent drift between Greenland and Eastern Canada: The system of channels that now separates the Arctic islands is evidently a drowned valley system modified by Pleistocene glaciation. The larger channels, many straight and arcuate-walled, are controlled by graben or rift-valley structures: such a structure also separates West Greenland from Baffin Island and formed Davis Strait and Baffin Bay; it is presumed to have been an offshoot of the Mid-Atlantic Ridge (Andrews et al. 1972). The timing of the initial rift has been estimated from Late Paleozoic to Early Tertiary, but since the paleomagnetic evidence is scarce, there is a considerable amount of uncertainty (Sharma and Athavale, 1975). This paper aims at presenting morphotectonic evidence in support of the above view on the genesis of Davis Strait.
Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Horst and graben are the elevated (hill) and depressed (valley) blocks of crust that lie between normal faults. A graben is also known as a ‘rift valley’. Both occur side by side. Horst and graben structure is formed by tensional stress and are dip-slip faults. A horst is rock up thrown by faulting and a graben is a block dropped down between faulting lines. A horst is the hillock between two grabens. Both horst and graben vary greatly in size and area. A graben may form a petroleum basin supported by horst-associated trap rocks.
Evaluation of the potential corrosivity of groundwater using an Analytic Hierarchy Process-based index
Published in Urban Water Journal, 2023
Aksaray city is located between North Latitudes 38°20″ and 38°23″ and East Longitudes 33°59″ and 34°3″ in the Central Anatolian Region of Turkey (Figure 1). The population of the city center is 239,523 according to 2022 population data. Aksaray province is in the middle climate zone and has a cold, continental climate type. The average temperature, precipitation rate and average annual evaporation rate in the study area, between 1927 and 2022 period, are 12.0 ◦C, 392 mm and 210 mm, respectively. Over the course of the year, the temperature typically varies from −6°C to 31°C and is rarely below −13°C or above 36°C. The study area has a flat topography in terms of geomorphology and is surrounded by high-elevation hills in the east due to tectonism. The most significant structural element of the region is the Lake Tuz Fault Zone (LTFZ), which lies in a 25–60° NW direction with a length of approximately 190–200 km (Kürçer and Gökten 2014). This fault zone consists of parallel faults showing a step-shaped half-graben or horst graben morphology.
Cenozoic volcanism, tectonics and mineralisation of Woodlark Island (Muyuw), eastern Papua
Published in Australian Journal of Earth Sciences, 2021
The middle Miocene (14–12 Ma) eruptions from the north-northeast-aligned Okiduse Volcanic Zone were localised in the similarly trending Kulumadau Horst and Graben Zone. Volcanic centres closely flank major structures in the 12.5 km wide extensional zone, suggesting a link between volcanism and extensional tectonics. It is not an obvious island arc settling and there are neither andesites nor an obvious subduction zone. Offshore, the Kulumadau Horst and Graben Zone is connected with the similarly trending Nubara Fault. This fault is the plate boundary between the Solomon Sea Plate and the Woodlark Plate. The contrasting volcanic deposits of the Okiduse Volcanic Group were erupted from a series of volcanic centres, including (from north to south) the Mt Kabat Eruptive Centre, Uvarakoi Caldera, Watou Mountain Eruptive Centre and Suloga Harbour Tuff Cone. The epithermal Busai and Kulumadau gold deposits are located in the Kulumadau Horst and Graben Zone. The deposits are hosted in lithologically favourable porous and permeable crystal lithic lapilli tuff beds in the Monasiy Tuff of the Uvarakoi Caldera.
Quantitative discrimination of normal fault segment growth and its geological significance: example from the Tanan Depression, Tamtsag Basin, Mongolia
Published in Australian Journal of Earth Sciences, 2018
H. X. Wang, X. F. Fu, S. R. Liu, R. Chu, B. Liu, P. P. Shi
Segments are, however, transient features in the evolution of a rift zone, as they grow and interact, they may link to form larger structures (Dawers & Anders, 1995; Kim & Sanderson, 2005; Pollard & Aydin, 1988). Therefore, the process of interaction is a necessary step in the evolution of a rift zone over a range of scales. The main basin geometries of rift systems (half-graben or graben) are controlled by major faults (Morley, 1995), with fault segment growth linkages controlling the evolution of depocentres (half-graben or graben) (Dawers & Underhill, 2000). Transfer zones are associated with such faults as transfer zones link major boundary faults that are located on opposite sides of rifts (Gawthorpe & Hurst, 1993) and can therefore cause variations in rift segment geometry (Morley, Nelson, Patton, & Mun, 1990; Rosendahl et al., 1986). As well as on basin formation and depositional patterns (Athmer & Luthi, 2011; Gawthorpe & Hurst, 1993; Morley, 1999, 2002), transfer zones also have considerable influence on hydrocarbon migration and trapping in rift systems (Coskun, 1997; Morley et al., 1990; Peacock & Sanderson, 1994).