A Paleogeographic and Depositional Model for the Neogene Fluvial Succession,Pishin Belt,Northwest Pakistan: Effect of Post Collisional Tectonics on Sedimentation in a Peripheral Foreland Setting     

Aimal K. KASI  Akhtar M. KASSI  Muhammad UMAR  Henrik FRIIS  Mohibullah MOHIBULLAH  Razzaq A. MANAN 《《地质学报》英文版》2018,92(2):499-518

Detailed facies analysis of the Neogene successions of the Pishin Belt (Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of the northwestern continental margin of the Indian Plate and the Afghan Block. During the Early Miocene, subaerial sedimentation started after the final closure of the Katawaz Remnant Ocean. Based on detailed field data, twelve facies were recognized in Neogene successions exposed in the Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee and floodplain facies associations. Facies associations and variations provided ample evidence to recognize a number of fluvial architectural components in the succession e.g., low‐sinuosity sandy braided river, mixed‐load meandering, high‐sinuosity meandering channels, single‐story sandstone and/or conglomerate channels, lateral accretion surfaces (point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to the oblique collision of the Indian Plate with the Afghan Block of the Eurasian Plate along the Chaman‐Nushki Fault. Post Miocene deformation of these formations successively caused them to contribute as an additional source terrain for the younger formations.  相似文献   

Sodalite—a mineralogical chameleon     

Henrik Friis 《Geology Today》2011,27(5):194-198

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Adaptive lives. Navigating the global food crisis in a changing climate     

Jonas Østergaard Nielsen  Henrik Vigh 《Global Environmental Change》2012,22(3):659-669

Human adaptation to climate change is gaining increasing academic as well as political attention. Understanding how and what people around the world adapt to is, however, difficult. Climate change is often, if not always, only one of a multiplicity of exposures perforating local communities. In Biidi 2, a small Sahelian village in northern Burkina Faso, climate variability have had a great influence on inhabitants’ lives since the major droughts of the early 1970s and 1980s. Tracing the intertwinement of drought, diminishing agricultural production and the need to buy food, this article explores how villagers attempt to attract development projects and negotiate with political parties in order to negate the impact of the global food crisis on their livelihoods. In doing so the article attempts to show how adaptation to climate variability is related to multiple, intersecting processes, and in this specific case is a matter of navigating changing socioeconomic factors. Using recent theory from social anthropology, adaptation is explored as a matter of social navigation. It is suggested that this theoretical approach might help nuance and elucidate how, and to what, local people around the world adapt.  相似文献   

Trends in chronic marine oil pollution in Danish waters assessed using 22 years of beached bird surveys     

Larsen JL  Durinck J  Skov H 《Marine pollution bulletin》2007,54(9):1333-1340

Beached bird surveys provide an important tool for monitoring the level of oil pollution at sea, which is the most significant observable cause of death for a large number of waterbird species and pose a serious threat to wintering seabird populations. Linear regression analyses of oil rates from the Danish 22 year dataset show a decline in the oil pollution level in offshore areas of the eastern North Sea and Skagerrak and in near-shore parts of the Kattegat; but a worsening in the offshore areas of the Kattegat. These results raise concern for species such as common scoter, velvet scoter, eider and razorbill, for which the Kattegat serves as a globally important wintering area. It is recommended that surveillance for oil spills is intensified in inner Danish waters, and that action is taken to make responses towards offenders faster, and penalties for oil seepage higher.  相似文献   

Surface velocity fields of active rock glaciers and ice-debris complexes in the Central Andes of Argentina     

Jan Henrik Blöthe  Christian Halla  Ellen Schwalbe  Estefania Bottegal  Dario Trombotto Liaudat  Lothar Schrott 《地球表面变化过程与地形》2021,46(2):504-522

Rock glaciers and transitional ice-debris complexes predominate the Central Andean landform assemblage, yet regional studies on their state of activity and their kinematics remain sparse. Here we utilize the national glacier inventory of Argentina to quantify surface velocity fields of 244 rock glaciers and 51 ice-debris complexes, located in the Cordón del Plata range, Argentina. Applying a feature-tracking approach to repeated RapidEye satellite imagery acquired between 2010 and 2017/18, we find mean displacement rates between 0.37 and 2.61 m year⁻¹ for 149 landforms, while for the remaining 146 features, surface movement remains below our level of detection. We compare our satellite-derived velocity fields with ground-truth data from two local field sites and find closely matching results in magnitude and spatial distribution. With average displacement of one-third of the active rock glaciers and ice-debris complexes exceeding 1 m year⁻¹, the region hosts an exceptional number of fast-flowing periglacial landforms, compared to other mountain belts. Using a random forest model, we test the predictive power of 25 morphometric and topoclimatic candidate predictors for modelling the state of activity of rock glaciers and ice-debris complexes on two different scales. For entire landforms and individual landform segments, constructed along displacement centrelines, we can predict the state of activity with overall accuracies of 70.08% (mean AUROC = 0.785) and 74.86% (mean AUROC = 0.753), respectively. While topoclimatic parameters such as solar radiation and elevation are most important for entire landforms, geometric parameters become more important at the scale of landform segments. Despite tentative correlations between local slope and surface kinematics, our results point to factors integrating slope and distance to the source to govern local deformation. We conclude that feature tracking in optical imagery is feasible for regional studies in remote regions and provides valuable insight into the current state of the Andean cryosphere. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

An Analysis of the Formation of Interconnecting Loops     

Jie Chen  Henrik Lundstedt  Yuanyong Deng  Peter Wintoft  Yin Zhang 《Solar physics》2011,273(1):51-68

Fifty interconnecting loops (ILs) that are induced by new-born active regions are investigated. The formation period of four ILs including two same-hemisphere interconnecting loops (HILs) and two transequatorial loops (TLs) are analyzed. The magnetic flux related with these loops is studied. Considering the active region pairs related with the IL as a magnetic system, the total magnetic flux has a tendency of increasing for this system, the signs of net magnetic flux tend to be opposite for the active region pairs. There is no difference between HILs and TLs in this aspect.  相似文献   

MRI channel flows and their parasites     

Henrik N. Latter  Pierre Lesaffre  Steven A. Balbus 《Monthly notices of the Royal Astronomical Society》2009,394(2):715-729

Local simulations of the magnetorotational instability (MRI) in accretion discs can exhibit recurrent coherent structures called channel flows. The formation and destruction of these structures may play a role in the development and saturation of MRI-induced turbulence, and consequently help us understand the time-dependent accretion behaviour of certain astrophysical objects. Previous investigations have revealed that channel solutions are attacked by various parasitic modes, foremost of which is an analogue of the Kelvin–Helmholtz instability. We revisit these instabilities and show how they relate to the classical instabilities of plasma physics, the kink and pinch modes. However, we argue that in most cases channels emerge from developed turbulence and are eventually destroyed by turbulent mixing, not by the parasites. The exceptions are clean isolated channels, which appear in systems near criticality or which emerge from low amplitude initial conditions. These structures can achieve large amplitudes and are only then destroyed, giving rise to eruptive behaviour.  相似文献   

Late Aptian long‐lived glacio‐eustatic lowstand recorded on the Arabian Plate     

Florian Maurer  Frans S.P. van Buchem  Gregor P. Eberli  Bernard J. Pierson  Madeleine J. Raven  Poul‐Henrik Larsen  Moujahed I. Al‐Husseini  Benoit Vincent 《地学学报》2013,25(2):87-94

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The Palaeoproterozoic Kangerluluk gold–copper mineralization (southeast Greenland): Pb and Nd isotopic constraints on its timing and genesis     

Henrik Stendal  Robert Frei  Mike A. Hamilton  Wulf U. Mueller 《Mineralium Deposita》2001,36(2):177-188

The Ketilidian Mobile Belt (KMB) in South Greenland is dominated by the Palaeoproterozoic Julianehåb Batholith (1,850–1,770?Ma) and is bordered by supracrustal sequences. The batholith is composed of granite, granodiorite, tonalite, diorite and subordinate gabbro and appinite and formed in a juvenile magmatic arc. The supracrustal rocks consist of psammites, pelites and subordinate, interstratified mafic volcanic rocks. A Rapakivi granite suite (1,755–1,735?Ma) intrudes them. Gold is an important metal in the KMB and occurs in various settings and element associations. Here, emphasis is placed on the Kangerluluk Cu–Au mineralization in the eastern part of the mobile belt. It is hosted within a remnant supracrustal succession dominated by redundant pillowed basalts. Structurally, a syn-volcanic association with gold can be distinguished from one that is clearly related to crosscutting quartz veins. In between, calc-silicate formation in the volcanic rocks occurred contemporaneously with a pervasive sericitization (bleaching) of leucocratic granitoids that are intrusive into the volcanic sequence. Bulk rock and mineral (sulfide) Pb isotope data are comparable in the Pb isotope space. The data define two groups of mineralization where one group is characterized by relatively higher ²⁰⁷Pb/²⁰⁴Pb at given ²⁰⁶Pb/²⁰⁴Pb ratios than the other. Pb stepwise leaching (PbSL) dating experiments performed on garnet and epidote associated with both groups of mineralization confirm the offset in the Pb isotope data. With the geochronological information from PbSL, the results indicate: (1) the initial gold mineralization was genetically related to metalliferous fluids associated with the emplacement of late intrusive stages of the Julianehåb Batholith (1,800–1,770?Ma); and (2) local remobilization of the initial mineralization (1,700–1,750) involved a Pb isotopically evolved fluid, which tentatively can be correlated with the intrusion of the Rapakivi granites in the area. Radiogenic Pb was not only found in altered host rocks but also in various sulfides, suggesting that fluids may have percolated through and/or originated from uranium-bearing graphitic schists which are abundant in the sedimentary package of the KMB. Lead isotopic results suggest that the Rapakivi granites may have supplied heat for renewed circulation of fluids within the supracrustal rock pile.  相似文献   

Modelling an exploited marine fish community with 15 parameters - results from a simple size-based model   总被引：1，自引：0，他引：1  

Pope  John G.; Rice  Jake C.; Daan  Niels; Jennings  Simon; Gislason  Henrik 《ICES Journal of Marine Science》2006,63(6):1029-1044

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