Downhill from Austin and Ely to Las Vegas: U-Pb detrital zircon suites from the Eocene–Oligocene Titus Canyon Formation and associated strata, Death Valley, California
Downhill from Austin and Ely to Las Vegas: U-Pb detrital zircon suites from the Eocene–Oligocene Titus Canyon Formation and associated strata, Death Valley, California
复制标题
从奥斯汀和伊利到拉斯维加斯的下坡：加利福尼亚州死亡谷始新世-渐新世提图斯峡谷组及相关地层的 U-Pb 碎屑锆石套件
DOI：
--
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Jens
中科院分区：
文献类型：
--
作者：
E. Miller;M. E. Raftrey;Jens
在一项旨在调查美国西部在盆岭断裂之前的地形和古地理变化的普查调查中，初步研究利用了来自始新世-渐新世提图斯峡谷组、其上覆单元和死亡谷附近的相关物的16个样品的碎屑锆石套的U-Pb年龄。提图斯峡谷组不整合地覆盖在加州和内华达州葬礼山和葡萄藤山的新元古代至泥盆纪地层上。样品采集自（1）提图斯峡谷的典型区域，（2）君主峡谷的源头，以及（3）在中部葬礼山脉边界峡谷断层的飞来峰中暴露的未命名新生代地层。在位置1和2的Titus峡谷组底部的红层和砾岩中，含有先前报道的38-37 Ma的化石，主要产出Sierran岩基时代的碎屑锆石（由三叠纪、侏罗纪和白垩纪的峰确定）。上覆的河道化河流砂岩、砾岩和少量湖相页岩、泥灰岩和石灰岩记录了源区在38-36 Ma左右或稍晚的突然变化，从更局部的谢尔兰弧源沉积物到北部的区域外源。含红色放射虫燧石、深色放射虫燧石和石英岩的碎屑表明其来源于北方内华达州的戈尔康达和罗伯茨山脉外来体。夹有砾岩的砂岩中含有越来越多的新生代锆石，这些锆石来源于内华达州奥斯汀和伊利纬度处向南迁移的破火山口形成喷发，最大沉积年龄（MDAs）在提图斯峡谷组顶部，范围为36至24 Ma。碳酸盐碎屑和富含灰层在上覆砾岩的Panuga组（其中包含一个以前的15.7 Ma灰流凝灰岩）中变得更加普遍。较高的，灰为主的Wahguyhe组的基础产生了MDA的14.4马。根据新的数据，中央葬礼山部分暴露了不同的单元序列，与位置1和2的Titus峡谷、Panuga和Wahguyhe组相关。灰流凝灰岩以上（未暴露）基地提供了MDA的34马，最年轻的样品产生了MDA的12.7马。年龄相关剖面之间的显着差异，以及基于地图的河道化证据，表明提图斯峡谷组和上覆单元可能代表河流、洪泛区和湖泊沉积，因为沉积物大多绕过该地区，向南移动到古近纪海岸线在莫哈韦沙漠。提图斯峡谷组中记录的源区和沉积相的深刻变化发生在熔结凝灰岩爆发岩浆活动期间，以及大陆分水岭从白垩纪弧轴向东移动到中部的新分水岭期间。内华达州响应热隆升和向地壳添加岩浆。这一隆起引发了向南流动的河流系统，为提图斯峡谷组和更高的单元提供了沉积物。
In a reconnaissance investigation aimed at interrogating the changing topography and paleogeography of the western United States prior to Basin and Range faulting, a preliminary study made use of U-Pb ages of detrital zircon suites from 16 samples from the Eocene–Oligocene Titus Canyon Formation, its overlying units, and correlatives near Death Valley. The Titus Canyon Formation unconformably overlies Neoproterozoic to Devonian strata in the Funeral and Grapevine Mountains of California and Nevada. Samples were collected from (1) the type area in Titus Canyon, (2) the headwaters of Monarch Canyon, and (3) unnamed Cenozoic strata exposed in a klippe of the Boundary Canyon fault in the central Funeral Mountains. Red beds and conglomerates at the base of the Titus Canyon Formation at locations 1 and 2, which contain previously reported 38–37 Ma fossils, yielded mostly Sierran batholith–age detrital zircons (defined by Triassic, Jurassic, and Cretaceous peaks). Overlying channelized fluvial sandstones, conglomerates, and minor lacustrine shale, marl, and limestone record an abrupt change in source region around 38–36 Ma or slightly later, from more local, Sierran arc–derived sediment to extraregional sources to the north. Clasts of red radiolarian-bearing chert, dark radiolarian chert, and quartzite indicate sources in the region of the Golconda and Roberts Mountains allochthons of northern Nevada. Sandstones intercalated with conglomerate contain increasing proportions of Cenozoic zircon sourced from south-migrating, caldera-forming eruptions at the latitude of Austin and Ely in Nevada with maximum depositional ages (MDAs) ranging from 36 to 24 Ma at the top of the Titus Canyon Formation. Carbonate clasts and ash-rich horizons become more prevalent in the overlying conglomeratic Panuga Formation (which contains a previously dated 15.7 Ma ash-flow tuff). The base of the higher, ash-dominated Wahguyhe Formation yielded a MDA of 14.4 Ma. The central Funeral Mountains section exposes a different sequence of units that, based on new data, are correlative to the Titus Canyon, Panuga, and Wahguyhe Formations at locations 1 and 2. An ash-flow tuff above its (unexposed) base provided a MDA of 34 Ma, and the youngest sample yielded a MDA of 12.7 Ma. The striking differences between age-correlative sections, together with map-based evidence for channelization, indicate that the Titus Canyon Formation and overlying units likely represent fluvial channel, floodplain, and lacustrine deposits as sediments mostly bypassed the region, moving south toward the Paleogene shoreline in the Mojave Desert. The profound changes in source regions and sedimentary facies documented in the Titus Canyon Formation took place during ignimbrite flareup magmatism and a proposed eastward shift of the continental divide from the axis of the Cretaceous arc to a new divide in central Nevada in response to thermal uplift and addition of magma to the crust. This uplift initiated south-flowing fluvial systems that supplied sediments to the Titus Canyon Formation and higher units.