Erosion of a high‐altitude,low‐relief area on the Korean Peninsula: implications for its development processes and evolution          下载免费PDF全文

Jongmin Byun  Arjun M. Heimsath  Yeong Bae Seong  Soo Yong Lee 《地球表面变化过程与地形》2015,40(13):1730-1745

The processes involved in the development of high‐altitude, low‐relief areas (HLAs) are still poorly understood. Although cosmogenic nuclides have provided insights into the evolution of HLAs interpreted as paleo‐surfaces, most studies focus on estimating how slowly they erode and thereby their relative stability. To understand actual development processes of HLAs, we applied several techniques of cosmogenic nuclides in the Daegwanryeong Plateau, a well‐known HLA in the Korean Peninsula. Our denudation data from strath terraces, riverine sediments, soils, and tors provide the following conclusions: (1) bedrock incision rate in the plateau (~127 m Myr^?1) is controlled by the incision rate of the western part of the Korean Peninsula, and is similar to the catchment‐wide denudation rate of the plateau (~93 m Myr^?1); (2) the soil production function we observed shows weak depth dependency that may result from highly weathered bedrock coupled with frequent frost action driven by alpine climate; (3) a discrepancy between the soil production and catchment‐wide denudation rates implies morphological disequilibrium in the plateau; (4) the tors once regarded as fossil landforms of the Tertiary do not reflect Tertiary processes; and (5) when compared with those of global paleo‐surfaces (<20 m Myr^?1), our rapid denudation rates suggest that the plateau cannot have maintained its probable initial paleo landscape, and thus is not a paleo‐surface. Our data contribute to understanding the surface processes of actively eroding upland landscapes as well as call into question conventional interpretations of supposed paleo‐surfaces around the world. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Some observations from radiometric ‘8 bit’ data of sediment thin sections based on alternative petrographic image analysis method   总被引：1，自引：0，他引：1  

Sudip Dey  Suvendu Ghosh  Chandrani Debbarma  Prasamita Sarkar  Mhu Aris Marfai  Sabyasachi Maiti 《Journal of Earth System Science》2009,118(2):163-173

This paper deals with the experiment of sediment microstructure analysis especially microfabric mapping by digital imaging. For that purpose the greyscale images (Red band from RGB combination) of the thin sections have been prepared from the selected 12 samples. The basis of this mapping is the reflectance capacity of different sediments which is influenced by the physical parameters like grain size and colour. The reflectances of different sediments are represented in digital format by different DN values from 0–255 within the radiometric ranges of ‘8 bit’ data. Density slicing has been chosen as the method of microstructure mapping in this research. This study shows that lower DN values normally present dark coloured coarser sand and clay while higher DN values present light coloured finer sediment samples. In the selected samples for this study the maximum DN value has been found from micaceous materials. Another remarkable thing observed from the microfabric mapping is that the presence of coarser sediments forms complex microfabric pattern than the finer sediments in the study area. Though this method have some demerits, still its simple technique can be very useful for accurate microstructure analysis.  相似文献   

2008 Best Paper Award     

Jong Hyuk Park  Jianhua Ma  Laurence T. Yang  Anind K. Dey 《Mathematical Geosciences》2009,41(8):955-956

Announcement

2008 Best Paper Award  相似文献   

On the Nature of the Compact Star in 4U 1728-34     

Li XD  Ray S  Dey J  Dey M  Bombaci I 《The Astrophysical journal》1999,527(1):L51-L54

The discovery of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binaries (LMXBs) with the Rossi X-Ray Timing Explorer has stimulated extensive studies of these sources. Recently, Osherovich & Titarchuk suggested a new model for kHz QPOs and the related correlations between kHz QPOs and low-frequency features in LMXBs. Here we use their results to study the mass-radius relation for the atoll source 4U 1728-34. We find that, if this model is correct, 4U 1728-34 is possibly a strange star rather than a neutron star.  相似文献   

Predicting Overbreak from Blast Vibration Monitoring in a Lake Tap Tunnel - A Success Story     

V. M. S. R. Murthy  Kaushik Dey 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(3):149-166

Tunnels are required to be constructed for meeting different human needs such as power generation, transportation, underground storage, sewage etc. The predominant method of excavation, world over, is drilling and blasting owing to its capability to meet changing geo-technical conditions. Irrespective of the purpose for which the tunnels are driven, all are plagued by overbreak problems. Tunnels driven for water conveyance in hydroelectric power projects, in particular, need to be excavated with minimum overbreak to minimise cost of permanent concrete lining. Thus, predicting overbreak assumes significant importance to design site-specific blasts for minimizing rock damage. This paper presents a brief review of existing PPV (Peak Particle Velocity) based blast-induced rock damage estimation criteria and attempts to outline the ground vibration threshold levels for overbreak/rock damage in a tunnel driven through compact basalt. Rock damage manifested as overbreak is measured and correlated with the possible threshold levels of PPV. Also, the PPV levels for crack initiation and widening are proposed. The case pertains to a lake tap horizontal tunnel of Koyna Hydro-electric Power Project, India which is a water feeder tunnel for a fully underground hydroelectric power project. The tunnel was driven under a shallow rock cover of average depth ranging from 20 to 25m beneath a fully charged water body. The parting rock is mainly compact basalt. Blasting was carried out in two rounds in a controlled manner, i.e., by limiting the maximum charge per delay based on ground vibration monitoring. Ground vibration generated with free face (in second round) has been modeled and a new ground vibration propagation equation is proposed for tunnel blasting including the effect of an extra free face. The threshold limits of PPV for different degrees of overbreak/rock damage are proposed from extrapolated vibration predictor equation. The actual overbreak in the tunnel, measured using a Planimeter, varied from 2.45 per cent to 17.75 per cent of the finished tunnel area. The predicted overbreak from extrapolated PPV measurements is compared against the measured overbreak to validate the proposed blast-induced rock damage (BIRD) assessment model. The PPV level for overbreak was found to exceed 2050 mm/s in compact basalt. A linear relationship between the overbreak and maximum charge per delay is also established to design a tunnel blast in similar formations.  相似文献   

The Occurrence of Agricultural Chemicals in Illinois' Rural Private Wells: Results from the Pilot Study     

E. Mehnert  S.C. Schock  M.L. Earnhardt  M.E. Caughey  S.F.J. Chou  W.S. Dey  G.B. Dreher  C. Ray 《Ground Water Monitoring & Remediation》1995,15(1):142-149

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Geochemical characteristics of mafic and ultramafic rocks from the Naga Hills Ophiolite,India:Implications for petrogenesis     

Ajoy Dey  M.Faruque Hussain  Mrigendra N.Barman 《地学前缘(英文版)》2018,9(2):517-529

The Naga Hills Ophiolite(NHO) represents one of the fragments of Tethyan oceanic crust in the Himalayan Orogenic system which is exposed in the Phek and Kiphire districts of Nagaland, India. The NHO is composed of partially serpentinized dunite, peridotite, gabbro, basalt, minor plagiogranite,diorite dyke and marine sediments. The basalts are mainly composed of fine grained plagioclase feldspar, clinopyroxene and orthopyroxene and show quenching and variolitic textures. The gabbros are characterized by medium to coarse grained plagioclase, orthopyroxene and clinopyroxene with ophitic to sub-ophitic textures. The ultramafic cumulates are represented by olivine, Cpx and Opx.Geochemically, the basalts and gabbros are sub-alkaline to alkaline and show tholeiitic features.The basalts are characterized by 44.1-45.6 wt.% of SiO_2 with 28-38 of Mg#, and the gabbros by38.7-43.7 wt.% of SiO_2, and 26-79 of Mg#. The ultramafic rocks are characterized by 37.4-52.2 wt.% of SiO_2, and 80-88 of Mg#. In multi-element diagrams(spidergrams) both basalts and gabbros show fractionated trends with strong negative anomalies of Zr. Nb. Sr and a gentle negative anomaly of P.However, the rare earth element(REE) plots of the basalts and gabbros show two distinct patterns. The first pattern, represented by light REE(LREE) depletion, suggests N-MORB features and can be interpreted as a signature of Paleo-Tethyan oceanic crust. The second pattern, represented by LREE enrichment with negligible negative Eu anomaly, conforms to E-MORB, and may be related to an arc tectonic setting. In V vs. Ti/1000, Cr vs. Y and AFM diagrams, the basalts and gabbros plot within Island Arc Tholeiite(IAT) and MORB fields suggesting both ridge and arc related settings. The ultramafic rocks exhibit two distinct patterns both in spidergrams and in REE plots. In the spidergram, one group displays highly enriched pattern, whereas the other group shows near flat pattern compared to primordial mantle. In the REE plot, one group displays steeper slopes [(La/Yb)N = 4.340-4.341], whereas the other displays moderate to flat slopes [(La/Yb)N = 0.97-1.67] and negative Eu-anomalies. Our study suggests that the ultramafic rocks represent two possible mantle sources(fertile and refractory).  相似文献   

Rainfall-induced landslide in the active frontal fold–thrust belt of Northwestern Himalaya,Jammu: dynamics inferred by geological evidences and Ground Penetrating Radar     

Yudhbir Singh  Ahsan Ul Haq  G. M. Bhat  S. K. Pandita  Arjun Singh  Rameshwar Sangra  Gulzar Hussain  S. S. Kotwal 《Environmental Earth Sciences》2018,77(16):592

Landslides are the most established geological hazards in the frontal fold–thrust belt of Northwestern Himalaya comprising of Siwaliks and Murree strata. The continuous rainfall from 2 to 6 September, 2014 caused a massive landslide at village Sadal in Udhampur district of Jammu and Kashmir state. The landslide occurred in the early morning of September 6, 2014, destroying entire Sadal habitation comprising 45 houses, and killing 41 people and more than 500 domestic animals. Google earth images of pre and post-landslide events along with the field measurements show the kinematics of upper and lower parts of the slide. Horizontal and vertical components of displacement and mode of failure suggest the landslide as of complex nature. The shallow subsurface geophysical imaging through Ground Penetrating Radar (GPR) survey shows the failure plane composed of friable mudstone bed underlain by massive mudstone and overlain by cross-bedded sandstone. The depth of debris material above the failure plane ranges from 6 m at Site S1a-b to 10 m at Site-S2b and 20 m at Site S3a. The velocity analysis of Site-3 shows four thick layers represented from bottom to surface by L1—sandstone (V?=?0.16 m/ns, travel time?=?356.36 ns), L2—mudstone (V?=?0.17 m/ns, travel time?=?288.48 ns), L3—massive mudstone (V?=?0.19 m/ns, travel time 220.68 ns), and L4—cross-laminated sandstone (V?=?0.20 m/ns, travel time?=?77.58 ns) overlaying the failure plane. The study shows the landslide occur along the western limb of a fold identified during the present work. We mapped an old landslide on the same limb which shows 5–6 m-thick subsurface debris material with thick rock fragments involved in the landslide process. The detailed geological and geophysical investigations suggest that both the landslides were triggered by extreme rain fall events.  相似文献   

Bayesian Markov Chain Random Field Cosimulation for Improving Land Cover Classification Accuracy   总被引：2，自引：0，他引：2  

Weidong Li  Chuanrong Zhang  Michael R. Willig  Dipak K. Dey  Guiling Wang  Liangzhi You 《Mathematical Geosciences》2015,47(2):123-148

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Climate and water balance change among public,private, and tribal lands within Greater Wild land Ecosystems across North Central USA     

Adhikari  Arjun  Hansen  Andrew J. 《Climatic change》2019,152(3-4):551-567

Climatic Change - The remaining wildlands in the North Central US include varying proportions of public, private, and tribal lands across water balance ecotones. These wildlands may be highly...  相似文献