The Teton Fault

Fault scarps on late Quaternary geomorphic surfaces present along the base of the Teton Range in Jackson Hole, Wyoming, attest to geologically recent movement of the Teton normal fault. This map depicts late Quaternary Teton fault scarps interpreted from field observations (2015–2018) and surface topography from two light detection and ranging (lidar) datasets (collected by Grand Teton National Park and Teton County Conservation District in 2014) which provide continuous lidar coverage for the entire map area. Although the map emphasizes fault scarps associated with the Teton fault, it also includes the Phillips Valley fault scarps, scarps in Jackson Hole that may have been caused by faulting or strong ground shaking from Teton fault earthquakes, and fault scarps west of Flagg Ranch associated with the Polecat Creek faults. The map shows the location of five paleoseismic (fault-trench) investigations conducted near Granite Canyon (Byrd, 1995), Leigh Lake (Zellman and others, 2017), Steamboat Mountain (Zellman and others, 2018), Jackson Hole Mountain Resort (the Buffalo Bowl site; DuRoss and others, 2018), and Antelope Flats (Thackray and others, 2019). Paleoseismic data from these sites help constrain the timing and displacement of Teton fault earthquakes. We also show where Larsen and others (2016) imaged the Teton fault with a seismic profile in Jenny Lake and the approximate locations of other possible paleoseismic features described by Pierce and others (1998) that are currently concealed by the high-water extent of Jackson Lake.We used lidar-derived digital elevation models (1-m cell size) to interpret and map fault scarps of likely late Quaternary age and discernible at a scale of 1:10,000 or finer. We depict these fault scarps using red lines where they have a clearly recognizable geomorphic expression, orange lines where the geomorphic expression is subtle, and purple lines where an indistinct surface expression results from surface modification from stream erosion and/or deposition. We do not show inferred traces connecting mapped fault scarps, such as those in areas where fault scarps may be concealed beneath lakes and landslides or removed by erosion. Likewise, although the lidar coverage extends west to the Wyoming-Idaho border, we did not attempt to interpret and map the extent of Quaternary faulting within Proterozoic and Paleozoic bedrock and Quaternary sediments west of the Teton and Phillips Valley faults or within the western portion of the John D. Rockefeller Memorial Parkway (west of Steamboat Mountain) where surface topography is complicated by extensive landsliding. We reviewed previous mapping of the Teton fault by Gilbert and others (1983), Love and others (1992), Ostenaa and others (1993), and Smith and others (1993), and the Phillips Valley fault by Schroder (1972), Love and others (1992), and Machette and others (2001), but we generally mapped the fault scarps in greater detail using the lidar datasets. Fault scarps depicted in eastern and southeastern Jackson Hole were modified from Gilbert and others (1983) and Wittke (2017). We examined, but ultimately excluded additional faults previously mapped throughout Jackson Hole (e.g., the east Gros Ventre fault; Love and others, 1992) as for most scarps, we could not rule out a glacial or fluvial origin.Our geomorphic mapping indicates a complex pattern of late Quaternary Teton fault scarps that continue north and south of the previously mapped extent of the fault. At the ground surface, the fault is characterized by a nearly continuous alignment of fault scarps that vertically offset late Pleistocene glacial, and late Pleistocene to Holocene alluvial-fan and landslide deposits. These scarps indicate that the surface trace of the Teton fault is at least 72 km long, from ~3 km southwest of Wilson to ~6 km north of Jackson Lake, near Steamboat Mountain. Locally, the fault trace is complex and includes fault bends, stepovers, and subparallel zones of synthetic and antithetic faulting. At a regional scale, fault scarps are obscured by a landslide north of Coulter Canyon (Ostenaa and others, 1993) and an apparent landslide north of Teton Village, and submerged beneath Jenny Lake and Jackson Lake. Bends in the fault trace occur at the mouths of Waterfall Canyon and Snowshoe Canyon, Leigh Lake, and between Phelps and Taggart Lakes. We mapped apparent fault stepovers near Phelps Lake and Leigh Lake.Our mapping includes groups of small (less than ~2 m high), generally north-trending scarps on late Quaternary surfaces in central Jackson Hole, between the Potholes and the National Elk Refuge, and north of Jackson Lake near Flagg Ranch. We interpreted a tectonic origin for these scarps as they continue across and vertically displace various Quaternary geomorphic surfaces (~mid-Pleistocene in age and younger; Pierce and others, 2018). Except for the scarps at the Potholes, the scarps in central Jackson Hole mostly face west, opposite (antithetic to) the Teton fault. Scarps mapped west of Flagg Ranch are likely the southern extent of the Polecat Creek faults, a subset of the Snake River Caldera faults (Ostenaa and others, 1993; Machette and others, 2001) which continue to the north beyond the extent of the lidar coverage. These scarps taper southward and become indistinct in the lidar on the north side of the Snake River.怀俄明州杰克逊霍尔地区特顿山脉山麓沿线出露的晚第四纪地貌面之上的断层崖，证明了特顿正断层（normal fault）近期的地质活动。本地图描绘了基于2015–2018年野外观测，以及2014年由大提顿国家公园与提顿县保护区采集的两套激光雷达（light detection and ranging, lidar）数据集解译出的晚第四纪特顿断层崖；该激光雷达数据实现了制图区域的全覆盖。尽管本地图重点展示与特顿断层相关的断层崖，但同时也包含了菲利普斯谷断层崖、杰克逊霍尔内可能由特顿断层地震引发的断层错动或强烈地面震动形成的崖体，以及弗拉格牧场以西与臭鼬溪断层（Polecat Creek faults）相关的断层崖。 地图标注了5处古地震（断层探槽）调查点位，分别位于花岗岩峡谷（Byrd, 1995）、利湖（Zellman等, 2017）、蒸汽山（Zellman等, 2018）、杰克逊霍尔山地度假村（野牛碗场址；DuRoss等, 2018）以及羚羊平原（Thackray等, 2019）。上述场址的古地震数据有助于约束特顿断层地震的发生时间与位移量。我们还标注了Larsen等（2016）在珍妮湖利用地震剖面成像特顿断层的位置，以及Pierce等（1998）描述的其他潜在古地震特征的大致位置——这些特征目前被杰克逊湖的高水位范围所覆盖。 本研究采用激光雷达衍生的数字高程模型（栅格单元尺寸1米）解译并编绘了可在1:10000或更大比例尺下识别的晚第四纪断层崖。我们以红色线条绘制具有清晰可辨地貌表达的断层崖，橙色线条绘制地貌表达较为隐晦的断层崖，紫色线条绘制因河流侵蚀和/或沉积作用导致地表改造而呈现模糊地表表达的断层崖。本研究未绘制连接已编绘断层崖的推断迹线，例如那些可能被湖泊、滑坡覆盖或因侵蚀作用消失的断层崖区域。同样，尽管激光雷达覆盖范围西至怀俄明州-爱达荷州边界，但我们未尝试解译并编绘特顿断层与菲利普斯谷断层以西的元古宙、古生代基岩及第四纪沉积物内的第四纪断层活动范围，也未编绘约翰·D·洛克菲勒纪念公园西路段（蒸汽山以西）的相关区域——该区域地表地形因广泛滑坡作用而变得复杂。 本研究参考了Gilbert等（1983）、Love等（1992）、Ostenaa等（1993）以及Smith等（1993）对特顿断层的前期编绘成果，以及Schroder（1972）、Love等（1992）与Machette等（2001）对菲利普斯谷断层的前期编绘成果，但整体上利用激光雷达数据集对断层崖进行了更细致的编绘。杰克逊霍尔东部与东南部的断层崖编绘参考了Gilbert等（1983）与Wittke（2017）的成果。本研究检视了此前在杰克逊霍尔全域编绘的其他断层（例如东格罗文特断层；Love等, 1992），但最终予以排除，因为对于多数崖体而言，无法排除其冰川或河流成因的可能性。 本地貌编绘结果表明，晚第四纪特顿断层崖的分布格局较为复杂，其延伸范围超出了此前编绘的断层南北边界。在地表，该断层以近乎连续分布的断层崖为特征，这些崖体垂直错断了晚更新世冰川沉积、晚更新世至全新世冲积扇沉积以及滑坡堆积体。这些崖体表明，特顿断层的地表迹线长度至少达72千米，从威尔逊西南约3千米处延伸至蒸汽山附近的杰克逊湖以北约6千米处。局部区域内，断层迹线较为复杂，包含断层弯曲、阶区以及同向和反向断层的亚平行带。 在区域尺度上，断层崖被库尔瑟特峡谷以北的滑坡（Ostenaa等, 1993）以及特顿村以北的疑似滑坡所遮挡，同时淹没于珍妮湖与杰克逊湖之下。断层迹线的弯曲出现在瀑布峡谷与雪鞋峡谷的入口处、利湖区域，以及菲尔普斯湖与塔格特湖之间。本研究在菲尔普斯湖与利湖附近识别出疑似的断层阶区。 本编绘工作包含杰克逊霍尔中部、壶穴与国家麋鹿保护区之间，以及杰克逊湖以北弗拉格牧场附近的晚第四纪地貌面上的小型（高度小于约2米）、整体呈北走向的崖体群。我们认为这些崖体具有构造成因，因为它们横穿并垂直错断了各类第四纪地貌面（年龄约为中更新世及更年轻；Pierce等, 2018）。除壶穴处的崖体外，杰克逊霍尔中部的崖体大多向西倾斜，与特顿断层反向（反向断层）。弗拉格牧场以西编绘的崖体可能是臭鼬溪断层的南部边界——该断层属于斯内克河破火山口断层（Snake River Caldera faults）的一个子集（Ostenaa等, 1993; Machette等, 2001），其向北延伸超出了激光雷达覆盖范围。这些崖体向南逐渐变细，在斯内克河以北的激光雷达数据中变得模糊不清。