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Regional Geologic Setting for the Boston Area

机译：波士顿地区的区域地质环境

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The understanding of the geologic development of southern New England has changed greatly over the past fifty years. Earlier, it was thought that the geology of the area developed primarily due to some great Devonian Acadian Orogeny followed by a lesser Permian Alleghanian Orogeny. Features ascribed to these events are found to have occurred much earlier and the revealed plate collision records additional complex events. The ancient edge of North America (Laurentia), formed in the Middle Proterozoic, and its younger offshore basin, collided with and was underthrust in the Late Proterozoic by the volcanic terrain of ancient northwest Africa (Gondwana). This collision changed most of this northwest edge of Gondwana into batholithic granite and squeezed out much of the intervening sea (see Figure 1-2). The subsequent rapid rise of this batholith and the formation of the Boston Basin were followed by a rising sea from the east that spread onto the land in the Cambrian. Further underthrusting at the end of the Ordovician closed any remaining gap between Gondwana and Laurentia and caused volcanism. Most of the resulting fused landmass (Pangea) then rose to form land or shallow coastal waters in the Early Silurian. The terrestrial setting continued the rest of the Paleozoic with extensional faulting and volcanism over most of the region. In the Mesozoic, the land began to fracture and slip into the developing Atlantic Ocean to the east.
机译：在过去的五十年中，对新英格兰南部地质发展的认识发生了巨大变化。早些时候，人们认为该地区的地质学发展主要是由于一些泥盆纪的阿卡迪亚造山运动，然后是较少的二叠纪的阿勒加尼造山运动。发现归因于这些事件的特征发生得早得多，并且所揭示的板块碰撞记录了其他复杂事件。北美的古边缘（劳伦西亚）形成于中元古代，其较年轻的近海盆地与元古代晚期相撞，并被古代西北非洲（冈瓦纳）的火山地带冲断。这次碰撞使冈瓦纳西北边缘的大部分地区变成了岩性花岗岩，并从大部分中间海中挤出（见图1-2）。随后，该岩基迅速崛起，并形成了波士顿盆地，随后是从东方升起的海浪扩散到寒武纪土地上。奥陶纪末期进一步的逆冲推挤缩小了冈瓦纳和劳伦蒂亚之间任何剩余的缝隙，并造成了火山作用。然后，大多数合成的陆块（Pangea）在志留纪早期形成了陆地或浅海。陆地环境延续了古生代的其余部分，并在该地区大部分地区发生了伸展断裂和火山作用。在中生代，这片土地开始破裂并滑入东部不断发展的大西洋。

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