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The Eastern North America Rift Basins are a series of sediment-filled ''aborted rifts'' created by large-scale continental extension. Their positions closely mirror the eastern coast of North America. ==Geology== Approximately 220 million years ago, during the late Triassic Period, the supercontinent Pangaea began to break apart. The focus of the rifting began somewhere between where present-day eastern North America and north-western Africa were joined. As in all rifting environments, grabens formed. Many of these grabens were created, but for some of them extension stopped before full rifting occurred. Where only partial rifting occurred, basins formed, analogous to the present-day Basin and Range Province in western United States. By definition, a basin is any area that collects sediments. These "aborted rifts" (rifts that are tectonically inactive and no longer collecting sediments) extend from North Carolina to Newfoundland. Along certain basins, rifting was not partial. Where full rifting occurred, the Atlantic Ocean was created. It is important to note that along these rifts, magmatic activity never stopped, as shown by the ongoing eruption of lava along the Mid-Atlantic Ridge. The basins are characterized by west-to northwest-dipping strata in the southern rifts (North Carolina to New York) while the northern ones (Connecticut to Nova Scotia) tend to dip northward. Many of the grabens have prominent signs of igneous activity, with diabase intrusions and basalt flows being quite common. Of these, only the Palisades Sill in the Newark Basin shows a layer with an enrichment in one mineral typically not found throughout the rest of the intrusion (in this case, the mineral is olivine). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eastern North America Rift Basins」の詳細全文を読む スポンサード リンク
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