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DAVID Applegate 《Basin Research》1995,7(3):269-280
The Northern Death Valley fault zone is a major right-lateral structure that has accommodated 70 km or more of regional transtensional deformation in Tertiary to Recent time. Extension parallel to its north-west transport direction in the Death Valley region of California has produced ‘pull-apart’ structures that are responsible for opening the central Death Valley rhombochasm. In several ranges along the length of the Northern Death Valley fault zone, there is also evidence for extension directed to the south-west, normal to strike-slip movement. Evidence from the Funeral, Grapevine and Cottonwood Mountains suggests that a significant amount of down-dip slip has occurred on the Northern Death Valley fault zone and parallel structures (together referred to as the Northern Death Valley fault system) coeval with the majority of right-lateral slip and transform-parallel extension. As a result of both these components of extension, a separate basin opened in northern Death Valley with an orientation and architecture very different from that of central Death Valley. In addition, the Northern Death Valley fault system may be responsible for the present topography of the Funeral and Grapevine Mountains. Transform-normal extension appears to be the result of a misorientation of the Northern Death Valley fault zone within the regional stress field over the past 6 Myr, as suggested by simple geometric calculations. 相似文献
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Jenny E. Goldstein Laura Graham Sofyan Ansori Yenni Vetrita Andri Thomas Grahame Applegate Andrew P. Vayda Bambang H. Saharjo Mark A. Cochrane 《Singapore journal of tropical geography》2020,41(2):190-208
Near-annual landscape-scale fires in Indonesia's peatlands have caused severe air pollution, economic losses, and health impacts for millions of Southeast Asia residents. While the extent of fires across the peatland surface has been widely attributed to widespread peatland drainage for plantation agriculture, fires that transition from surface into sub-surface soil-based fires are the source of the most dangerous air pollution. Yet the mechanisms by which this transition occurs have rarely been considered, particularly in diversely managed landscapes. Integrating physical geography methods, including active fire scene evaluations and hydrological monitoring, with qualitative methods such as retrospective fire scene evaluations and semi-structured interviews, this article discusses how and why sub-surface peat fire transition occurs in an intensively altered peatland ecosystem in Indonesia's Central Kalimantan province. We demonstrate that variable water table levels and flammable surface vegetation (fire fuels) are co-produced socio-political and biophysical phenomena that enable the conditions in which surface fire is likely to transition into peat fire and increase landscape vulnerability to ongoing, uncontrollable annual fires. This localized understanding of peat fire transition counters normative causal narratives of tropical fire such as ‘slash-and-burn’, with implications for the management of new fire regimes in inhabited landscapes. 相似文献
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Summary Those who lament the absence of an agreed, secure definition of globalization are likely to remain in a state of despondency. In this paper, it is argued that the meaning of the term 'economic globalization' is context-bound and that, depending upon the referent chosen to fix the term, the geographies of either manufacturing or service enterprises move into focus in what is, to till intents and purposes, a 'home-region' affair. 相似文献
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Evolution of the Himalayan foreland basin, NW India 总被引：3，自引：0，他引：3
This paper provides new information on the evolution of the Himalayan foreland basin in the under‐reported region of the Kangra and Subathu sub‐basins, NW India. Comparisons are made with the better documented co‐eval sediments of Nepal and Pakistan to build up a broader picture of basin development. In the Subathu sub‐basin, shallow marine sediments of the Palaeocene–lower Lutetian Subathu Formation are unconformably overlain by the continental alluvial Dagshai and Kasauli Formations and Siwalik Group. The start of continental deposition is now dated at younger than 31 Ma from detrital zircon fission track data, thereby defining the duration of this major unconformity, which runs basin‐wide along strike. Final exhumation of these basin sediments, as thrusting propagated into the basin, occurred by 5 Ma constrained from detrital apatite fission track data. In the Kangra sub‐basin, the Subathu Formation is not exposed and the pre‐Siwalik sediments consist of the Dharamsala Group, interpreted as the deposits of transverse‐draining rivers. In this area, there is no evidence of westerly axial drainage as documented for coeval facies in Nepal. Similar to data reported along strike, facies analysis indicates that the sediments in NW India represent the filled/overfilled stages of the classic foreland basin evolutionary model, and the underfilled stage is not represented anywhere along the length of the basin studied to date. 相似文献
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Katherine C. Glover Thomas V. Lowell Gregory C. Wiles Donald Pair Patrick Applegate Irena Hajdas 《Quaternary Research》2011,76(3):401-410
Many paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~ 16–11 ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~ 22–16 ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this gap. The basal radiocarbon dates from these cores show that initial ice retreat from the maximal last-glacial ice extent occurred by 22 ka, and numerous sites that are ~ 100 km inside this limit were exposed by 18.9 ka. Post-glacial environmental changes were identified as stratigraphic or biologic changes in select cores. The strongest signal occurs between 18.5 and 14.6 ka. These Midwestern events correspond with evidence to the northeast, suggesting that initial deglaciation of the ice sheet, and ensuing environmental changes, were episodic and rapid. Significantly, these changes predate the onset of the Bølling postglacial warming (14.8 ka) as recorded by the Greenland ice cores. Thus, deglaciation and landscape change around the southern margins of the Laurentide Ice Sheet happened ~ 7 ka before postglacial changes were felt in central Greenland. 相似文献
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Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa 总被引：75，自引：0，他引：75
Laboratory experiments on natural, hydrous basalts at 1–4 GPa constrain the composition of “unadulterated” partial melts of eclogitized oceanic crust within downgoing lithospheric slabs in subduction zones. We complement the “slab melting” experiments with another set of experiments in which these same “adakite” melts are allowed to infiltrate and react with an overlying layer of peridotite, simulating melt:rock reaction at the slab–mantle wedge interface. In subduction zones, the effects of reaction between slab-derived, adakite melts and peridotitic mantle conceivably range from hybridization of the melt, to modal or cryptic metasomatism of the sub-arc mantle, depending upon the “effective” melt:rock ratio. In experiments at 3.8 GPa, assimilation of either fertile or depleted peridotite by slab melts at a melt:rock ratio 2:1 produces Mg-rich, high-silica liquids in reactions which form pyrope-rich garnet and low-Mg# orthopyroxene, and fully consume olivine. Analysis of both the pristine and hybridized slab melts for a range of trace elements indicates that, although abundances of most trace elements in the melt increase during assimilation (because melt is consumed), trace element ratios remain relatively constant. In their compositional range, the experimental liquids closely resemble adakite lavas in island-arc and continental margin settings, and adakite veins and melt inclusions in metasomatized peridotite xenoliths from the sub-arc mantle. At slightly lower melt:rock ratios (1:1), slab melts are fully consumed, along with peridotitic olivine, in modal metasomatic reactions that form sodic amphibole and high-Mg# orthopyroxene. 相似文献
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Grahame J. Larson John Menzies Daniel E. Lawson Edward B. Evenson Nathan R. Hopkins 《Boreas: An International Journal of Quaternary Research》2016,45(2):235-251
The macro‐ and micro‐sedimentology of a supraglacial melt‐out till forming at the Matanuska Glacier was examined in relationship to the properties of the stratified basal zone ice and debris from which it is originating. In situ melting of the basal ice has produced a laminated to bedded diamicton consisting mainly of silt. Macroscopic properties include: discontinuous laminae and beds; lenses of sand, silt aggregates and open‐work gravel; deformed and elongate clasts of clay; widely dispersed pebbles and cobbles, those that are prolate usually with their long axes subparallel to parallel to the bedding. Evidence for deformation is absent except for localized bending of beds over or under rock clasts. Microscopic properties are a unique element of this work and include: discontinuous lineations; silt to granule size laminae; prolate coarse sand and rock fragments commonly with their long axis subparallel to bedding; subangular to subrounded irregular shaped clay clasts often appearing as bands; sorted and unsorted silt to granule size horizons, sometimes disrupted by pore‐water pathways. Limited deformation occurs around rock clasts and thicker parts of lamina. This study shows that in situ melting of debris‐rich basal ice can produce a laminated and bedded diamicton that inherits and thereby preserves stratified basal ice properties. Production and preservation of supraglacial melt‐out till require in situ melting of a stagnant, debris‐rich basal ice source with a low relief surface that becomes buried by a thick, stable, insulating cover of ice‐marginal sediment. Also required are a slow melt rate and adequate drainage to minimize pore‐water pressures in the till and overlying sediment cover to maintain stability and uninterrupted deposition. Many modern and ancient hummocky moraines down glacier of subglacial overdeepenings probably meet these process criteria and their common occurrence suggests that both modern and pre‐modern supraglacial melt‐out tills may be more common than previously thought. 相似文献