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Global Geology
2024 Vol.27 Issue.3
Published 2024-08-25
121
Preliminary results of lithological and palynological study of Svobodny, ancient man’s parking relic in Amur region, Russia
Kovalenko S. V. 1,Kezina T. V. 2*,Kryuchko E. I. 1 and Mironov M. A. 1
A single-layer monument Svobodny, ancient man＇s parking lot-1, discovered in 2021 as part of archaeological work to study the zone of economic development of the Amur region was investigated lithologically and palynologically. Based on the results of geomorphological analysis of the territory, the study of artifacts, palynological data, as well as analogy with previously identiffed and sufffciently studied relics in the region, the existence of the Osinoozersk late Neolithic culture in this territory is assumed. The time of its expansion in the Amur region is determined within the framework of the second half of the IV millennium BC to the ffrst half of the II millennium BC. The preliminary results of palynological analysis suggest the existence of a temperate climate here, was close to the modern one, which does not contradict the reconstructed paleoclimate and environments of the region during the Holocene period.
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2024 Vol. 27 (3): 121-131 [
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132
Changes of grain size from peat proffle in eastern mountainous area over past 2000 years, Jilin Province, Northeast China
ZHANG Xinrong,WANG Jiayu,PING Shuaifei and LI Yaran
Plenty of high-resolution paleoclimate investigations of the last thousand years were carried out to potentially predict future climate changes. Mountainous ombrotrophic peatland is one of the best recorders for high-resolution paleoclimate studies in the forest area. Grain size analysis was carried out on ombrotrophic peat proffle in the eastern mountainous region of Jilin Province, Northeast China. The peat proffle lasts the past 2 000 a by four radiocarbon (AMS14 C) ages. The results showed that the inorganic minerals in the peat proffle are mainly silt, with some contribution from clay and a minor amount of sand, which are mainly due to wind dust and suspended transportation. Two paleoclimate stages are found in this peat proffle by phytolith analysis, peat cellulose isotope research and historical documents: ca. 45–1550 AD, relatively cold period; ca. 1550 AD–present, relatively warm period. This ffnding is important for the initial study of paleoclimatic changes over the last 2 000 a in the mountainous area of eastern mountainous area, Jilin Province, Northeast China.
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2024 Vol. 27 (3): 132-144 [
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Migration images guided high-resolution velocity modeling based on fully convolutional neural network
DU Meng,MAO Weijian,YANG Maoxin and ZHAO Jianzhi
Current data-driven deep learning (DL) methods typically reconstruct subsurface velocity models directly from pre-stack seismic records. However, these purely data-driven methods are often less robust and produce results that are less physically interpretative. Here, the authors propose a new method that uses migration images as input, combined with convolutional neural networks to construct high-resolution velocity models. Compared to directly using pre-stack seismic records as input, the nonlinearity between migration images and velocity models is signiffcantly reduced. Additionally, the advantage of using migration images lies in its ability to more comprehensively capture the reffective properties of the subsurface medium, including amplitude and phase information, thereby to provide richer physical information in guiding the reconstruction of the velocity model. This approach not only improves the accuracy and resolution of the reconstructed velocity models, but also enhances the physical interpretability and robustness. Numerical experiments on synthetic data show that the proposed method has superior reconstruction performance and strong generalization capability when dealing with complex geological structures, and shows great potential in providing efffcient solutions for the task of reconstructing high-wavenumber components.
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2024 Vol. 27 (3): 145-153 [
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UAV-based transient electromagnetic 3D forward modeling and inversion and analysis of exploration capability
WEI Laonao, LIU Yunhe* and ZHANG Bo
Unmanned aerial vehicle transient electromagnetic (UAV-TEM) is a novel airborne exploration method that offers advantages such as low cost, simple operation, high exploration efffciency and suitability for near-surface exploration in complex terrain areas. To improve the accuracy of data interpretation in this method, the authors conducted a systematic three-dimensional (3D) forward modeling and inversion of the UAV-TEM. This study utilized the finite element method based on unstructured tetrahedral elements and employed the second-order backward Euler method for time discretization. This allowed for accurate 3D modeling and accounted for the effects of complex terrain. Based on these, the influence characteristics of ffight altitudes and the sizes, burial depths, and resistivities of anomalies are compared and analyzed to explore the UAV-TEM systems’ exploration capability. Lastly, four typical geoelectrical models of landslides are designed, and the inversion method based on the Gauss-Newton optimization method is used to image the landslide models and analyze the imaging effect of the UAV-TEM method on landslide geohazards. Numerical results showed that UAV-TEM could have better exploration resolution and ffne imaging of nearsurface structures, providing important technical support for monitoring, early warning, and preventing landslides and other geological hazards.
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2024 Vol. 27 (3): 154-166 [
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Horizontal-to-vertical spectral ratio inversion method based on multimodal forest optimization algorithm
CHEN Xuanning, HAN Fuxing, GAO Zhenghui *,SUN Zhangqing and HAN Jiangtao
The exploration of urban underground spaces is of great signiffcance to urban planning, geological disaster prevention, resource exploration and environmental monitoring. However, due to the existing of severe interferences, conventional seismic methods cannot adapt to the complex urban environment well. Since adopting the single-node data acquisition method and taking the seismic ambient noise as the signal, the microtremor horizontal-to-vertical spectral ratio (HVSR) method can effectively avoid the strong interference problems caused by the complex urban environment, which could obtain information such as S-wave velocity and thickness of underground formations by fitting the microtremor HVSR curve. Nevertheless, HVSR curve inversion is a multi-parameter curve fftting process. And conventional inversion methods can easily converge to the local minimum, which will directly affect the reliability of the inversion results. Thus, the authors propose a HVSR inversion method based on the multimodal forest optimization algorithm, which uses the efffcient clustering technique and locates the global optimum quickly. Tests on synthetic data show that the inversion results of the proposed method are consistent with the forward model. Both the adaption and stability to the abnormal layer velocity model are demonstrated. The results of the real ffeld data are also veriffed by the drilling information.
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2024 Vol. 27 (3): 167-176 [
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