Geologic Map of the Vail West quadrangle, Eagle County, Colorado

This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range.
Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit.
Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the Rio Grande rift system in Colorado.
In the southwestern part of the map area, a diapiric(?) exposure of the Eagle Valley Evaporite exists and chaotic faults and folds suggest extensive dissolution and collapse of overlying bedrock, indicating the presence of a geologic hazard. Quaternary landslides are common and indicate that landslide hazards are widespread in the area, particularly where old slide deposits are disturbed by construction. The late Pliocene(?) landslide that consists largely of a smectitic upper Morrison Formation matrix and boulders of Dakota Sandstone is readily reactivated. Debris flows are likely to invade low-standing areas within the towns of Vail and West Vail where tributaries of Gore Creek issue from the mountains on the north side of the valley.

本数据集为美国地质调查局（USGS）科罗拉多西部I-70走廊合作地质填图项目的组成部分，涵盖韦尔西7.5分幅（Vail West 7.5' quadrangle）1:24000比例尺新型地质图，对戈尔山脉（Gore Range）西南翼区域的地层、构造与地质灾害开展了全新解译。

区内基岩地层包括中新世凝灰质沉积岩、中生界与上古生界沉积岩，以及未划分的早元古代（？）变质沉积岩与火成岩。凝灰质岩石赋存于断层倾斜地块中。仅残存少量达科他砂岩（Dakota Sandstone）、莫里森组（Morrison Formation）、恩特拉达砂岩（Entrada Sandstone）与钦利组（Chinle Formation）的露头残块，覆盖于二叠-宾夕法尼亚纪马隆组（Maroon Formation）与宾夕法尼亚纪明顿组（Minturn Formation）的红层之上；上述红层形成于戈尔断裂带以东的古前岭（Ancestral Front Range）侵蚀作用。在图幅西南部区域，近端相的明顿组逐渐过渡为远端相的鹰谷组（Eagle Valley Formation）与鹰谷蒸发岩盆地相。原被定义为明顿组顶部的雅克山灰岩段（Jacque Mountain Limestone Member），无法追索至西南方向的相变界面处。广泛分布的表层沉积包括皮因代尔冰碛与布尔湖冰碛（Pinedale and Bull Lake Tills）、冰缘沉积、土流堆积、普遍发育的混杂堆积（diamicton deposits）、第四纪滑坡堆积体，以及一处规模宏大的疑似上新世晚期滑坡堆积体。韦尔镇区域地表经人工改造程度极高，因此专门设置了改造地表单元以表征该类地表类型。

拉拉米德造山运动（Laramide movement）使戈尔断裂带的活动再次复苏，在古生界与中生界地层中形成了一系列与断裂带走向平行的北西向开阔背斜与向斜。可见发育有倾向东北的第三纪正断层，该类断层与戈尔山脉及东北部蓝河谷（Blue River valley）内的同类断层产状一致，推测其与科罗拉多州里奥格兰德裂谷（Rio Grande rift system）北段形成过程中的伸展变形作用密切相关。

在图幅西南部区域，存在一处底辟（？）成因的鹰谷蒸发岩露头，杂乱分布的断层与褶皱表明上覆基岩发生了广泛的溶蚀与塌陷，这指示了一处地质灾害隐患。第四纪滑坡分布广泛，表明该区域滑坡灾害普遍存在，尤其是旧滑坡堆积体因工程活动遭到扰动的区域。这套疑似上新世晚期的滑坡体主要由上莫里森组的蒙脱石基质与达科他砂岩砾石组成，极易发生复活。碎屑流极易涌入韦尔与西韦尔镇内的低洼区域，此处戈尔溪（Gore Creek）的支流从山谷北侧的山地中流出。