The Baiyun Sag is the deepest sag in the Pearl River Mouth Basin in northern continental margin of South China Sea,with the maximum sediment thickness over 12.5 km above the basement including >6.5 km sediments abo...The Baiyun Sag is the deepest sag in the Pearl River Mouth Basin in northern continental margin of South China Sea,with the maximum sediment thickness over 12.5 km above the basement including >6.5 km sediments above the 30 Ma breakup unconformity.According to the theoretical models for the rifted basins,the post-rift subsidence is driven solely by the thermal contraction and can be calculated as the function of the lithospheric stretching factor.A method combining the forward modeling and reverse backstripping was designed to estimate lithospheric stretching factor.Using the 2D forward modeling based on the flexural cantilever model,we simulated the multi-rifting process of the Baiyun Sag with constrain of the backstripped profiles.By doing this the lithospheric stretching factor was obtained,and then the theoretical post-rift subsidence was calculated.The calculated theoretical subsidence was much smaller than the observed subsidence given by backstripping.Along the 1530 line in the Baiyun Sag,the anomalous post-rift subsidence is over 2 km in the sag center,and varies slightly to the north and south edges of the sag.This suggests that the anomalous post-rift subsidence continues beyond the sag both in the continental shelf to the north and in the continental slope to the south.The sensitivity tests in the forward modeling process indicate that only the use of low-angle faults (≤13°) can we simulate the shape of the backstripped profile.展开更多
南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉...南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉张模型计算的理论裂后沉降值进行对比,发现白云主凹中心的裂后异常沉降量最大超过2.6km,白云南凹最大异常沉降量接近2km,高于白云凹陷北部边缘的异常沉降。凹陷东部的裂后沉降作用强于凹陷西部。对沉降曲线的研究发现,白云凹陷在中中新世(16.5～10.5Ma)期间有一段沉降明显加速的过程,白云南凹尤为明显,可能与南海扩张停止事件有关。白云凹陷发育了巨厚的沉积,并且呈韧性伸展状态,本文认为下地壳流可能是导致白云凹陷裂后异常沉降最主要的因素。展开更多
We investigate sedimentological and tectonic processes at the central High Atlas, in order to understand their functioning and to build a geodynamic model that placed the area in its current geological frame.The analy...We investigate sedimentological and tectonic processes at the central High Atlas, in order to understand their functioning and to build a geodynamic model that placed the area in its current geological frame.The analysis used here is based on the numerical enhancement of a Landsat image where the main goal is to map surface sedimentary deposits throughout the central High Atlas in order to delimit the large geological structures. The sediment distribution throughout central High Atlas indicates that this one is a large tectonic subsiding basin, where the ongoing tectonic events and the geodynamical evolution remain to be explained by other prospecting techniques.3-D structure velocities obtained by local seismic tomography and enhancement techniques of gravimetric anomalies are used to explore and define deep structure beneath the central High Atlas. The goal is to establish the evolution of the deep structure related to the geodynamical processes. Modest crustal thickness variation beneath the central High Atlas(~20-~40 km) define by local tomography and gravimetric anomalies, confirms that, a major part of the lower crust is detached into the lithosphere by delamination. Gravimetric anomaly, local seismic tomography and vertical cross sections throughout the central High Atlas, suggest that the lower crust detached is related to the broken slab of remain northward subduction beneath High and Middle Atlas. Meanwhile, extrusions of heated Asthenosphere materials induce the rifting stage concomitant to tectonic subsidence of the basin.展开更多
文摘The Baiyun Sag is the deepest sag in the Pearl River Mouth Basin in northern continental margin of South China Sea,with the maximum sediment thickness over 12.5 km above the basement including >6.5 km sediments above the 30 Ma breakup unconformity.According to the theoretical models for the rifted basins,the post-rift subsidence is driven solely by the thermal contraction and can be calculated as the function of the lithospheric stretching factor.A method combining the forward modeling and reverse backstripping was designed to estimate lithospheric stretching factor.Using the 2D forward modeling based on the flexural cantilever model,we simulated the multi-rifting process of the Baiyun Sag with constrain of the backstripped profiles.By doing this the lithospheric stretching factor was obtained,and then the theoretical post-rift subsidence was calculated.The calculated theoretical subsidence was much smaller than the observed subsidence given by backstripping.Along the 1530 line in the Baiyun Sag,the anomalous post-rift subsidence is over 2 km in the sag center,and varies slightly to the north and south edges of the sag.This suggests that the anomalous post-rift subsidence continues beyond the sag both in the continental shelf to the north and in the continental slope to the south.The sensitivity tests in the forward modeling process indicate that only the use of low-angle faults (≤13°) can we simulate the shape of the backstripped profile.
文摘南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉张模型计算的理论裂后沉降值进行对比,发现白云主凹中心的裂后异常沉降量最大超过2.6km,白云南凹最大异常沉降量接近2km,高于白云凹陷北部边缘的异常沉降。凹陷东部的裂后沉降作用强于凹陷西部。对沉降曲线的研究发现,白云凹陷在中中新世(16.5～10.5Ma)期间有一段沉降明显加速的过程,白云南凹尤为明显,可能与南海扩张停止事件有关。白云凹陷发育了巨厚的沉积,并且呈韧性伸展状态,本文认为下地壳流可能是导致白云凹陷裂后异常沉降最主要的因素。
基金supported by the Institut Scientifique, Rabat, Morocco
文摘We investigate sedimentological and tectonic processes at the central High Atlas, in order to understand their functioning and to build a geodynamic model that placed the area in its current geological frame.The analysis used here is based on the numerical enhancement of a Landsat image where the main goal is to map surface sedimentary deposits throughout the central High Atlas in order to delimit the large geological structures. The sediment distribution throughout central High Atlas indicates that this one is a large tectonic subsiding basin, where the ongoing tectonic events and the geodynamical evolution remain to be explained by other prospecting techniques.3-D structure velocities obtained by local seismic tomography and enhancement techniques of gravimetric anomalies are used to explore and define deep structure beneath the central High Atlas. The goal is to establish the evolution of the deep structure related to the geodynamical processes. Modest crustal thickness variation beneath the central High Atlas(~20-~40 km) define by local tomography and gravimetric anomalies, confirms that, a major part of the lower crust is detached into the lithosphere by delamination. Gravimetric anomaly, local seismic tomography and vertical cross sections throughout the central High Atlas, suggest that the lower crust detached is related to the broken slab of remain northward subduction beneath High and Middle Atlas. Meanwhile, extrusions of heated Asthenosphere materials induce the rifting stage concomitant to tectonic subsidence of the basin.
