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四万十超群位于九州、四国和本州两条成对变质岩带的东南,中间隔着秩父、三宝山带及佛像构造线,是一条轻度变质的沉积岩带。该变质沉积岩带始于西南诸岛,穿过九州、四国、纪伊半岛、赤石和关东山脉,延伸直达房总半岛,面积与加利福尼亚弗兰西斯科组及大峡谷层系合起来的面积相当。白垩纪的下群在太平洋一侧与早第三纪—早中新世的上群邻接。以砂岩和泥岩为主的四万十沉积因周期性俯冲作用而变形成为开放型和等斜型的褶皱以及冲断席,前者向着东南闭合,后者则局部含玄武质枕状熔岩和放射虫燧石。九州和四国的砂岩随其地层位置的不同而表现出显著的组分变化。根据长石的含量,可以区剐白垩纪和第三纪的砂岩。砂岩岩石学和古水流资料表明,四万十超群的沉积可能来自西北面的前寒武纪片麻岩,而在早白垩纪时,四万十地体位于南部朝鲜以东时,构成其沉积源的或许是朝鲜半岛较老的中生代花岗岩。西南日本内带花岗岩的顶部侵蚀作用可能也促成了白垩纪及其后的沉积作用。较年青的四万十沉积中富含石英、分选良好的砂,可能是从较老四万十建造中循环返回的。巨厚的四万十沉积层系是在白垩纪,接着(在更南面)在早第三纪和早中新世堆积在加积杂岩体、海沟坡折、海沟内坡和海沟背景上的弧前盆地内各种环境中的。早第三纪弧前盆地内(弧)侧较浅水域中沉积下来的是向上变粗加厚的三角洲层系。更向海的较深水域内堆积起了海底水道和冲积扇复杂体、坡底滑动沉积和夹有燧石的红色页岩。海沟坡折处为夹有玄武岩和泥混滑岩的混杂岩,而加积基底上的海沟内壁栖留盆地则为向上变粗的复理层、混滑泥岩相和央变玄武岩的混杂岩所充填。库拉板块断续周期性的向北俯冲控制着当时的沉积作用和变形作用。造成狭长弧内盆地的引张和断陷阶段与挤压阶段交替发生。今天,在东南日本岸外的海底阶地、海沟坡折、海沟内坡(包括栖留盆地)及南海海槽的充填层中已发现了类似的沉积环境。
Shimanto Supercity is located in the southeast of Kyushu, Shikoku and Honshu as two pairs of metamorphic rock belts, separated by the Chichibu, Sambo and Buddhism tectonic lines, and is a slightly altered sedimentary rock belt. The metamorphic sedimentary rock belt started in the Southwest Islands and crossed Kyushu, Shikoku, Kii Peninsula, Akaishi and Kanto Mountains and extended directly to Fongzheng Peninsula. The area of the metamorphic sedimentary rock belt is similar to the area of the Francisco France Formation and the Grand Canyon in California . The Lower Cretaceous subgroup on the Pacific side adjoins the upper Tertiary-Early Miocene herd. Sandstone and mudstone-dominated 40,000 sediments were deformed into open and isostrophic folds and thrusts due to periodic subduction, with the former closing toward the southeast and the latter locally containing basaltic pillow lava and radioactive chert flint. The sandstones of Kyushu and Shikoku show significant compositional changes depending on their location. Depending on the feldspar content, Cretaceous and Tertiary sandstones can be zoned. Sandstone petrology and palaeo-flow data indicate that the deposition of 40,000 ultrasonography may have originated from Precambrian gneiss in the northwest, whereas in the early Cretaceous, the 40,000th is located in the east of southern Korea, which may constitute the sedimentary source The older Mesozoic granites in the Korean Peninsula. Top-eroded granite in the southwestern Japan may also contribute to Cretaceous and subsequent sedimentation. The younger 40,000 deposits are enriched with quartz and well-sorted sand, possibly returning cyclically from the older 40,000. The massive 40,000 sedimentary system was deposited in the Cretaceous and then (in the south) earlier in the Tertiary and Early Miocene in the accretionary complex, trenches, trenches and trenches Basin in a variety of environments. Early Triassic Pre-arcuate basin (arc) side of the shallow waters deposited in the upper down thicker thickened delta system. Seafloor waterways and alluvial fan complexes, sloping sloping deposits and flint-bearing red shales accumulate in more deep waters to the sea. The trough slope is a melange with basaltic and muddy slips, while the inner wall of the trenches on accretionary basement is filled with upwards thickening flysch, mixed slip mudstone facies and central deformation basalt melange . The periodic northward subduction of the Kula plate controls the sedimentation and deformation at that time. As a result, the extensional and fault-depression stages of the long-arc-arc basin alternate with the extrusion stage. Today, a similar depositional environment has been found in the fill of submarine terraces, trench slips, trench inner slopes (including the Habitat) and the South China Sea trough off the southeast Japan.