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全新世大暖期海侵边界的位置确定对研究区域古沉积环境演化和应对未来不确定的海平面上升对海岸带地区造成的影响提供了重要基础性前提.古海侵边界的确切位置可以通过追踪具有连续地层区域的海相地层尖灭点实现.本文选取莱州湾东岸具有钻孔数据和典型古海岸线地貌标志的区域为试验场,提出了一种探地雷达(GPR)追踪大暖期海侵边界的方法.结果显示,选取探测深度7—8m、图像分辨率0.3m的100MHz超强地面耦合(RTA)非屏蔽天线能够较好地识别海侵体系界面,结合已有钻孔Y61和现场探挖的浅钻,能够获得海侵沉积层由海向陆逐渐向上延伸、直至尖灭的层位位置变化信息的剖面图像.依据已确立的方法,在莱州湾南岸已有钻孔ZK305附近也取得了较好的效果.海侵形成的粉砂、细砂和泥的薄互层以楔形侵入至古今陆相沉积层间,在雷达图像上会形成明显的反射特征.方便快捷的探地雷达技术结合部分钻孔资料可用于海相层、古海岸线位置的精确测定,为古海岸线位置不确定的区域提供纵向直观、层序地层方面的判定依据.
The location determination of the Holocene Megathermal transboundary boundary provides important preconditions for the evolution of the paleo-sedimentary environment in the study area and the impact of the uncertain sea level rise on the coastal zone in the future. The exact position of the ancient transgression boundary can be tracked With continuous stratigraphic strata in the marine strata.This paper chooses the borehole data of the east coast of Laizhou Bay and the typical paleogeographic landform as the experimental field and proposes a GPR tracing of the warm-season sea The results show that the 100 MHz super strong ground coupling (RTA) unshielded antenna with the detection depth of 7-8 m and the image resolution of 0.3 m can well identify the interface of the transgressive system. Combining the existing borehole Y61 and the site Exploration of shallow drilling can obtain a cross-sectional image of the transgressive sedimentary layer gradually extending upwards from sea to land until the pinnacle of the change of horizon position information has been established. According to the established method, a hole near ZK305 has been drilled in the south bank of Laizhou Bay The results show that the thin interbeds of silt, fine sand and mud formed by transgression intrude into the paleo-modern terrestrial sedimentary layers with wedges, and the obvious reflection features will be formed on the radar images. The quick and easy GPR technology combined with some borehole data can be used to accurately determine the position of the marine strata and the ancient coastline, and provide the longitudinal visualization and the judgment of sequence stratigraphy for the region where the location of the ancient coastline is uncertain.