Journal of Asian Earth Sciences: X最新文献

We investigate the Palaeocene succession of the Hazara Basin (Northern Pakistan) to better understand the impact of climate change on marine carbonate-producing organisms. These shallow-water carbonates, deposited during the Late Palaeocene, before the onset of the Palaeocene-Eocene Thermal Maximum, were studied using a quantitative approach to highlight changes in the skeletal assemblage. We recognise a decrease in the abundance of colonial corals and green calcareous algae and an increase in larger benthic foraminifera and red calcareous algae from the early Thanetian to the late Thanetian. Increasing temperatures may represent a plausible cause for the decline of the more sensitive colonial corals in favor of the more tolerant larger benthic foraminifera. A similar pattern is observed in most successions deposited along the margins of the Neotethys Ocean, suggesting a connection with the Late Palaeocene environmental changes that heralded the PETM hyperthermal event. Our stratigraphic analysis of the Hazara Basin strata suggests that the biotic turnovers occurred during the Palaeocene – Eocene transition started already before the onset of the Palaeocene Eocene Thermal Maximum as recorded by the geochemical proxies.

A ground model of a shallow landslide in rainfall-induced slope failure of Thungsong, Nakhon Si Thammarat, southern Thailand is developed through an integrated geophysical approach, utilising electrical resistivity tomography and P-wave seismic refraction tomography (SRT) methods. Those two methods were applied to assess landslide structure and study deformation mechanisms along four profiles. Beside the four profiles there is another profile, which was acquired near an borehole and used for the calibration with geological data. Our results show subsurface structures in terms of the ground model used to determine stratigraphic layers, zones of saturation or groundwater table, and significant differences between the landslide slip material and the underlying bedrock. The clay-rich zones (resistivity less than 500 Ωm) in the colluvium on the relatively steep slope, show enhanced potential for landslides. This silty clay plays an important role for landslide activation in this site. Moreover, a combination of steep slopes, shallow basement rocks overlain by clay-rich colluvium, and seasonally high rain fall leads to landslides in the region. The ground model produced by geophysical imaging for this region achieves a comprehensive understanding of the structure and lithology of a complex landslide system and overcomes the limitations of remote-sensing data or isolated intrusive sampling techniques alone.

The detection and prioritization of optimal favorable areas for the ground follow-up stage are among the most challenging issues in the early stages of any mineral exploration program. A common approach to identify the favorable mineralized zones is to create and integrate independent evidential predictor layers using knowledge or data driven approaches. The method proposed in current study is not only capable of detecting favorable zones, but also provides reliable ranking of the best favorable areas to focus in the next exploration stage. For this purpose, a two-step sequential Fuzzy-Fuzzy TOPSIS approach, which deploys the merits of both Multi-Criteria Decision Making (MCDM) and Fuzzy logic inference methodologies simultaneously, is proposed. In the first step, the favorable porphyry copper mineralizations in the east of the well-known Sarcheshmeh porphyry copper mine, are detected through combining evidential layers including geological, remote sensing data, geophysical and geochemical data using fuzzy logic integration approach. As a result of the first step, a number of twenty prospects with the highest porphyry copper favorability membership were selected and inputted into the TOPSIS and fuzzy-TOPSIS algorithms. Subsequently, the chosen prospects were prioritized and ranked according to their scores acquired by each technique of the aforementioned approaches separately. The performance of each approach was evaluated thorough comparison with the known ground porphyry copper mineralizations. The results indicated the capability of the proposed approach not only in detecting favorable porphyry copper mineralization prospects consistent with the previously detected porphyry Cu mineralization but also rank them based on their priorities.

We present a study on gravity data from the Observatory Superconducting Gravimeter (OSG-051) located at MPGO Ghuttu in the Garhwal Himalaya, India. Ambient noise observed at this site is compared with other worldwide SGs and computed seismic noise magnitude for the OSG-051. Instrumental noise has been observed at frequencies ranging from ∼0.0239 to ∼0.03207 Hz in the form of parasitic mode for the lower and upper sensors of SG, whose quality factor has been estimated in different modes of oscillations. The signal is enhanced at noise reduction below 2.0 mHz using local barometric pressure data and modelled tidal effect of the site. Other seismic noise factors are discussed through data analysis of OSG-051. OSG-051 and trillium 240 Broad Band Seismometer data are analysed and compared in the seismic normal mode frequency band. Several observations have been made regarding noise sources that affect the gravity data in the seismic normal mode’s frequency band. Residual gravity data after removal of atmospheric pressure, tidal, and co-seismic effects, respond very well to long-period seismometers than any conventional seismometer. This characteristic and low noise level of the MPGO Ghuttu site makes it a suitable station for long-period seismometer studies.

This study describes geomorphic expressions and constructs the schematic evolution of the Northern Sumatran Fault based on the development of transverse drainage basins and streams. This fault is a 400-km NW-SE right-lateral strike-slip fault with three segments, namely the Aceh and Seulimeum Faults in the northern section and the Tripa Fault in the southern section. The two faults at the northern section are sub-parallel and they link at the southeast termination of the latter fault. The examination on the geomorphic expressions comprised the fault configuration, stream deflections, and the delineation of landforms based on their genesis and geometry. This study applied drainage basin relief ratio (Rh), drainage basin volume-to-area ratio (R_va), and transverse stream profile analysis (normalized stream profile, qualitative interpretation of the profile shapes, stream concavity index (SCI), stream gradient, and knickpoint distribution) for investigating the development of transverse drainage basins and streams. For constructing the schematic evolution, this study evaluates drainage maturity level from the applied methods to interpret relative timing of basin formation. This study suggests that the Aceh and Tripa Faults constituted the initial configuration and they propagated to the southeast and northwest, respectively, before merging. The Seulimeum Fault, which formed subsequently, propagated to the northwest after merging with the Aceh Fault at its southeast termination. This study also infers that fault section with lower drainage maturity coincides with greater numbers of earthquakes.

This paper presents recently obtained palynological results regarding to the evolution of vegetation of the Khanka Depression in the Holocene. Radiocarbon-dated pollen records evidence that the evolution of vegetation in this area was more complicated than one has previously thought. As a result of a rapid increase in heat supply in the Early Holocene, the plants of the Manchurian flora, primarily Ulmus davidiana, Ulmus laciniata, Quercus mongolica, and Pinus koraiensis, began to expand to the Khanka Depression. However, Sphagnum mires with Betula grandulosa, Betula pubescens, and sparse forests of Larix, still remained in plains and valleys. Picea jezoensis, Pinus pumila, Betula grandulosa, Betula alnobetula, Betula pubescens, Pinus pumila and Larix were widespread in the mountains. During the Middle Holocene these cold-tolerant plants of the north-boreal flora, completely disappeared. Broad-leaved and fir-pine forests have become widespread. The vegetation of the Khanka Depression compared with modern one was characterized by great diversity of broad-leaved plants. At the beginning of the Late Holocene cooling has caused the expansion of Betula grandulosa, Betula alnobetula, Abies nephrolepis, Picea jezoensis, Betula pubescens, Betula costata, and Alnus hirsuta. The areas of forb meadows expanded on the plains. Larch sparse forests, thickets with domination of Betula grandulosa and Sphagnum mires reappeared. However, some thermophilic plants, such as Pinus koraiensis, Abies nephrolepis, Quercus mongolica, Juglans mandshurica, Ulmus davidiana, and Ulmus laciniata have survived. Since 1 300 cal BP, vegetation of the Khanka Depression began to degrade due to fires, plowing of the land, and deforestation.

The producing fields often observe early decline due to many misapprehended factors concerning structural interpretation, facies identification, and proper estimation of geological properties. The accuracy of the estimation of these characteristics is critical for enhanced recovery. An integrated approach based on well identified potential lithofacies distribution in relation to seismic trace responses and accurate fluid estimation is vital. In the present study, gas-bearing sands are appraised for their reservoir characteristics within a complex anticline structure. The faulted anticline's hanging wall provided suitable locations for optimum gas entrapment; however, its connection with the footwall through lateral ramps allows the aquifer's early encroachment into the reservoir. For enhanced recovery, the combination of well-derived petrophysical parameters with seismic extracted responses provided insight into the producing facies with quantitative fluids identification using fluid replacement modeling (FRM) and their amplitude variation with offset (AVO) responses. The reliable AVO responses of substituted fluids comprising 85% gas with 15% brine are observed for identified potential sands, classifying sands as class-II. Similarly, the intercept (A), gradient (B), and product (A*B) of angle dependent seismic traces were mapped within the Pab Formation and showed amplitude anomalies for porous channelized gas-bearing sands. Finally, crossplotting intercept-gradient volumes differentiated the gas-bearing sands and precisely demarcated the identified gas sands throughout the field, with confirmation at producing well locations. Hence, the integrated assessment of the outcomes resulting from structural interpretation, petrophysical evaluation, and seismic trace valuation can be readily employed for distinguishing the producing sand facies in complex structures and demarcating risk-efficient zones.

The evaluation of the geothermal potential of the granitic rocks is important in long-term sustainable renewable energy projects due to increasing energy demand. The Eastern Pontides Orogenic Belt in NE Turkey contains a variety of granitic plutons changing in age, size, and composition. In this paper, we discussed the temporal and spatial distribution of radiogenic heat production by using the contents of heat-producing elements (U, Th, K) of the granitic plutons. The average U, Th, and K concentrations for the granitic plutons are 2.97 ± 0.95 ppm, 13.48 ± 3.48 ppm and 2.69 ± 0.47 wt% for Paleozoic plutons, 1.83 ± 0.98 ppm, 8.58 ± 5.10 ppm and 1.77 ± 0.80 wt% for Jurassic plutons, 5.24 ± 1.64 ppm, 26.02 ± 6.43 ppm and 3.17 ± 0.49 wt% for Cretaceous plutons, and 3.82 ± 0.90 ppm, 15.79 ± 4.27 ppm and 2.88 ± 0.40 wt% for Eocene plutons, respectively. Radiogenic heat production rates are 1.43–2.73 µW/m³ for Paleozoic plutons, 0.74–1.70 µW/m³ for Jurassic plutons, 0.66–6.28 µW/m³ for Cretaceous plutons and 1.15–5.22 µW/m³ for Eocene plutons. The studied plutons were classified as low- to moderate heat-producing granitoids. However, some Cretaceous and Eocene granitic plutons with radiogenic heat production values of 5.22–6.28 µW/m³ are considered as high heat-producing granitoids. The thermal indications in the region can be related to radiogenic heat generation and the neotectonic activity of the region. Considering the large volume of the Cretaceous- and Eocene- aged granitic plutons in the Eastern Pontides Orogenic Belt, the moderate to high radiogenic heat production of the granitic plutons in some areas has a significant geothermal impact and can be considered as the potential of enhanced geothermal systems for the future energy demand of the region.