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首页> 外文期刊>Geosphere >Spatially variable syn- and post-Alleghanian exhumation of the central Appalachian Mountains from zircon (U-Th)/He thermochronology
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Spatially variable syn- and post-Alleghanian exhumation of the central Appalachian Mountains from zircon (U-Th)/He thermochronology

机译：来自锆石（U-Th）/ He Thermochronology的空间可变的Syn-和Allghanian山脉中央山脉的挖掘

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摘要

To assess spatial and temporal patterns of Phanerozoic orogenic burial and subsequent exhumation in the central Appalachian Mountains, we present mid-temperature zircon (U-Th)/He (ZHe; closure temperature [ T C ] = 140–200 °C) dates for 10 samples along a 225 km, strike-perpendicular transect spanning the Appalachian Plateau, Valley and Ridge, Blue Ridge, and Piedmont physiographic provinces in West Virginia and western Virginia. Ranges of single-grain ZHe dates exhibit an eastward younging trend from 455–358 Ma in the Pennsylvanian Appalachian Plateau to 336–209 Ma in the Valley and Ridge, 298–217 Ma in the Blue Ridge, and 186–121 Ma in the Piedmont. Within the Pennsylvanian Appalachian Plateau, detrital ZHe dates are older than corresponding depositional ages, thus limiting postdepositional burial temperatures to less than 160 °C. These ZHe dates capture predepositional mid-Paleozoic cooling signatures, indicating provenance from either recycled Taconic or Acadian basin strata or mid-Paleozoic Appalachian terranes. Across the Valley and Ridge and western Blue Ridge provinces, reset Permian detrital ZHe dates feature flat date-effective uranium correlations that suggest rapid Alleghanian cooling initiating prior to 270 Ma. ZHe dates within the Valley and Ridge are more than 100 m.y. older than previously reported regional apatite fission-track dates, reflecting a protracted period of stable post-Alleghanian thermal conditions within the foreland. By contrast, post-Triassic single-grain ZHe dates in the interior Piedmont document rapid postrift cooling, likely resulting from both the relaxation of an elevated geothermal gradient and exhumation from rift-flank uplift. The spatial discontinuity between stable synrift thermal conditions in the Valley and Ridge and rapid cooling in the Piedmont suggests that rift-flank uplift and cooling were concentrated outboard of the foreland within the Piedmont province.
机译：为了评估在中央阿巴拉契亚山脉显生造山埋藏和随后的折返空间和时间模式，我们本中温锆石（U-TH）/赫（哲;封闭温度[TC] = 140-200℃）日期10沿着225公里处，走垂直断面跨越阿巴拉契亚高原，山谷和山脉，蓝岭样品，并在西弗吉尼亚州和西弗吉尼亚山前地貌省份。单粒哲日期范围从表现马455-358在宾夕法尼亚州阿巴拉契亚高原向东变年轻的趋势，以336-209马云在山谷和山脉，298-217马蓝岭和186-121马山前。内宾夕法尼亚阿巴拉契亚高原，碎屑哲日期是比相应的沉积年龄更老，从而限制了沉积后埋藏的温度到小于160℃。这些哲日期捕获predepositional中期古生代冷却签名，指示从任一再循环Taconic的出处或阿卡迪亚盆地地层或中间古生代阿巴拉契亚地体。在整个山谷和山脉和西部的蓝岭省，复位二叠纪碎屑哲日期功能，可快速提示冷却Alleghanian开始之前270马平日期有效铀的相关性。在山谷和山脉内喆日期超过100 M.Y.比先前报道的地区磷灰石裂变径迹日期，反映了稳定后Alleghanian热条件前陆内旷日持久的时期老。与此相反，在内部皮埃蒙特文档快速裂谷后三叠单粒哲日期冷却，有可能从提升地热梯度和折返从裂谷侧面隆起的两个张弛所致。在谷和脊同裂谷期稳定的热条件和快速在山前冷却之间的空间不连续性表明，裂谷侧面隆起和冷却浓缩皮埃蒙特省内前陆的外侧。

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