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首页> 外文期刊>Pure and Applied Geophysics >Geophysical Constraints on the Location and Nature of the North Saharan Flexure in Southern Tunisia
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Geophysical Constraints on the Location and Nature of the North Saharan Flexure in Southern Tunisia

机译：突尼斯南部北撒哈拉弯曲的位置和性质的地球物理约束

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摘要

Gravity data, integrated with seismic refraction/reflection data, well data and geological investigations, were used to determine the location of the paleogeographic boundary between the Precambrian Saharan domain and the younger Tunisian Atlas domain. This boundary (North Saharan Flexure or NSF) has not been as clearly defined as it has been to the west in Algeria and Morocco. The gravity data analysis, which included the construction of complete Bouguer and residual gravity anomaly maps, revealed that the Atlasic domain is characterized by relative negative gravity anomalies and numerous linear gravity trends implying a thick and deformed sediment cover. The Saharan domain is characterized by relatively positive gravity anomalies with few gravity trends implying a thin and relatively undeformed sediment cover. An edge-enhancement analysis of the residual gravity anomalies revealed that the NSF is characterized by a series of discontinuous east- and northwest-trending linear anomalies south of 34°N that are not related to the well-known faults within the Gafsa and Accident de Medenine regions. Based on the continuity of the amplitudes of seismic reflection data and the trends of the residual gravity anomalies, the NSF is not an abrupt discontinuity but a series of step faults dipping toward the Atlasic domain. To obtain a more quantitative representation of the southern edge of Tunisian Atlas, a regional gravity model constrained by two wells and seismic reflection/refraction data was constructed along a north-south trending profile which confirms the presence of thicker sediments north of the NSF. Our analysis shows that the NSF has controlled the depositional environment of the sedimentary rocks within the region since at least Triassic time and has acted as a barrier to Atlasic deformation south of the NSF. The NSF is considered an important tectonic feature that has controlled the paleogeographic evolution of the southern margin of the Tethys Ocean, and it continues to be active today based on seismicity hazard studies.
机译：重力数据与地震折射/反射数据，井数据和地质调查相结合，用于确定前寒武纪撒哈拉域和年轻的突尼斯阿特拉斯域之间的古地理边界位置。该边界（北撒哈拉挠曲或NSF）的定义不像在阿尔及利亚和摩洛哥的西部那样明确。重力数据分析（包括完整的布格和残余重力异常图的构建）显示，Atlasic域的特征是相对负重力异常和众多线性重力趋势，这意味着沉积物覆盖层厚而变形。撒哈拉域的特征是相对正的重力异常，几乎没有重力趋势，这意味着沉积物薄且相对未变形。对残余重力异常的边缘增强分析表明，NSF的特征是在北纬34°以南的一系列不连续的东西向线性异常，与加夫萨和事故事故中心的已知断层无关。麦德宁地区。基于地震反射数据振幅的连续性和残余重力异常的趋势，NSF不是突然的间断，而是一系列向Atlasic域倾斜的阶跃断层。为了获得突尼斯地图集南部边缘的更定量表示，沿着两口井的约束建立了区域重力模型，并沿着北-南趋势剖面构造了地震反射/折射数据，这证实了NSF北部存在较厚的沉积物。我们的分析表明，NSF至少从三叠纪开始就控制了该地区内沉积岩的沉积环境，并成为NSF南部Atlasic变形的屏障。 NSF被认为是控制特提斯海洋南缘古地理演化的重要构造特征，并且根据地震危险性研究，今天它仍然活跃。

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