A glacial sequence stratigraphic model for temperate, glaciated continental shelves
A glacial sequence stratigraphic model for temperate, glaciated continental shelves
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温带冰川大陆架的冰川层序地层模型
DOI：
10.1144/gsl.sp.2002.203.01.12
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
J. Cooper
中科院分区：
文献类型：
--
作者：
R. Powell;J. Cooper
温带冰期大陆架本质上是复杂的盆地，因为它们不仅具有典型的低纬度硅化作用，产生沉积记录和沉积结构，而且还具有冰川作用叠加的结果。对于这些环境，冰川系统域被定义并与冰川前进和后退特征相关联，然后可以相对于其他外力的变化进行评估。我们定义了由边界不整合面分隔的冰川最大退缩面（GMaST）、退缩面（GRST）、最小退缩面（GMiST）和前进面（GAST）系统域，它们分别是接地线退缩面（GRS）、最大（冰川）退缩面（MRS）和冰川推进面（GAS）。每一个冰川进退序列都被一个区域性显著的不整合面、一个冰川侵蚀面或其等效的整合面所包围。准层序母带在陆架上各不相同，但包括以接地线运动为主的相。相基可能有冰下沉积到1 GES以上，这是gast的主要相；然而，收银机通常不存在。虽然碎屑碎屑通常与接地线沉积系统有关，但由于冰川融水的主导作用，GRST演替主要是由砾石、碎石和分选差的砂组成的分选矿床。这些沉积物通常具有银行或楔形/扇形的几何形状。它们在外大陆架上形成了复盖断裂，并在大陆架上形成了海岸体系的逆行堆积。河岸上覆盖着冰川韵律岩，包括薄碎屑、浊积岩、旋流岩和旋流岩，也许还有扇形到片状几何形状的冰山漂流岩。在它们上面是覆盖着的柏石泥，它们逐渐变成了副冰泥。GMiST发生在冰川退缩到陆地或峡湾时。GMiST在近岸地区以以三角洲和硅质陆架体系为主的海陆体系的进积沉积为代表，在近海地区则以缩合剖面为代表。GAST是GRST相序列的逆序列，但也是最可能在前进过程中被侵蚀的层段。
Abstract Temperate, glaciated continental shelves are by nature complex basins in that they not only have typical low-latitude siliciclastic processes acting to produce a sedimentary record and depositional architecture, but they also have the consequences of glacial action superimposed. For these settings glacial systems tracts are defined and related to glacial advance and retreat signatures, which can then be evaluated relative to changes in other external forces. We define glacial maximum (GMaST), retreat (GRST), minimum (GMiST) and advance (GAST) systems tracts separated by bounding discon-formities, which are respectively, the grounding-line retreat surface (GRS), the maximum (glacial) retreat surface (MRS) and the glacial advance surface (GAS). Each glacial advance and retreat sequence is bounded by a regionally significant unconformity, a glacial erosion surface (GES), or its equivalent conformity. Parasequence motifs vary across the shelf but include facies dominated by the movement of grounding lines. Facies motifs may have subglacial till above a GES and this is the main facies of the GMaST; however, tills are commonly absent. Although diamictic debrites are often associated with groundingline deposystems, the GRST succession is dominated by sorted deposits of gravel, rubble and poorly sorted sands due to the dominance of glacial meltwater. These deposits commonly have the geometry of banks or wedges/fans. They form the offlap-break at the outer continental shelf and also form a retrogradational stacking of bank systems on the shelf. Banks are capped by glacimarine rhythmites including thin debrites, turbidites, cyclopsams and cyclopels and perhaps iceberg-rafted varvites in fan to sheet-like geometries. Above these are draped sheets of bergstone muds that grade into paraglacial muds. The GMiST occurs with glacial retreat onto land or into fjords. The GMiST is represented in nearshore areas by progradational deposits of paralic systems dominated by deltaic and siliciclastic shelf systems, and in offshore areas by condensed sections. The GAST is represented by the inverse of the GRST facies succession, but is also the most likely interval to be eroded during readvance.