山东半岛南部近岸海域新近系以来地震层序及沉积特征

    SEISMIC SEQUENCE AND SEDIMENTARY CHARACTERISTICS OF THE NEOGENE IN THE OFFSHORE AREA OF SOUTH SHANDONG PENINSULA

    • 摘要: 利用近年来在山东半岛南部近海采集的浅地层剖面、单道地震等资料,进行精细处理与解释,结合前人的研究成果,系统地揭示了研究区内自新近系以来沉积层序。结果表明:研究区主要处在千里岩隆起背景上,第四系和新近系直接覆盖于印支期变质岩系上,由于新近系底界面为向东南缓倾的构造形态,故新近纪以来的海侵层不断向西北超覆,各期地层在厚度图上均表现为北西薄、南东厚的楔形体;全新统地层全区均有分布,最大厚度为15.5 m,整体呈现出楔形体的形态,是最近一次海侵形成的海相地层;上更新统地层的分布受下部构造形态影响较大,在乳山以东海域缺失,整体上在研究区东南部较厚,近岸处减薄,平均厚度约60 m;中更新世沉积仍受到区域构造背景的控制,越靠近南黄海盆地北部凹陷其沉积越厚,反之越薄,直至尖灭消失;下更新世的沉积格局类似于中更新统,也受控于区域构造背景,其分布范围较中更新统更小更局限;上新世时期,黄海海域继续稳定沉降,构造稳定,期间沉积了一层厚度均匀、平坦的地层,厚度大体呈向西北减薄的楔形,等值线变化相对比较平缓;中新统地层作为裂后坳陷沉积的首套地层,其厚度分布特征与新近系底界面埋深基本一致。

       

      Abstract: This study aims to revealing the sedimentary sequence since Neogene in the coastal waters off the southern Shandong Peninsula, China. Detailed processing and interpretation are performed for shallow stratigraphic sections and recently acquired single-channel seismic data for the study area. Results show that the study area is mainly located on the Qianliyan Uplift, with the Quaternary and Neogene strata directly overlying the Indosinian metamorphic rock series. Since the bottom boundary of the Neogene strata is gently dipping to the southeast (SE), and transgressive beds since Neogene have a continuous overlapping pattern towards northwest (NW) direction, the strata of different ages all show a wedge shape pattern thinner in NW and thicker in SE in isopach maps. Holocene strata are widely distributed throughout the study area with a maximum thickness up to 22.5m. They also show a wedge shape in general, representing the marine strata formed by latest transgression. The distribution of Upper Pleistocene strata is strongly affected by underground structures. They pinch out in the waters to the east of Rushan. This set of strata as a whole is relatively thick in the southeast of the study area and gets thinner offshore, with a mean thickness of approximately 60 m. The Middle Pleistocene deposits are still under the control of regional tectonic settings, which become increasingly thicker towards the sag in the northern South Yellow Sea Basin and become thinner until pinching out. The depositional pattern of the Lower Pleistocene strata is similar to the Middle Pleistocene under the control of regional tectonics. However, the former is smaller and more localized in distribution. During Pliocene, the Yellow Sea area continued to subside steadily and remained stable tectonically; a layer of flat strata was deposited in rather uniform thickness in a NW-thinning wedge shape, with relatively moderate changes in thickness. The Miocene strata, as the first deposits of post-rift depression deposits, present a similar thickness distribution pattern with the depth of the Neogene bottom boundary.

       

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