Across the Mojave Desert of southeastern California, outcrops of the Cambrian middle member of the Wood Canyon Formation preserve the deposits of pre-vegetation braided-fluvial and braid-delta environments. One 78-meter-thick section in the southern Marble Mountains, documented here through detailed stratigraphic logging, facies analysis, architectural panels based on “Structure-from-Motion” models, and a suite of paleocurrent and accretion-surface measurements, provides insight into the development of a river-dominated, wave- and tide-influenced braid delta at the distal end of a continent-scale braidplain. In contrast to other pre-Devonian braid-delta strata, in which mudrock is largely absent, the greater part of the middle member system contains over 5% mudstone. Four facies associations, FA4–7, constitute the middle member section and represent (in order of stratigraphic height) a braidplain-to-delta transition (FA4), proximal braid delta (FA5), distal braid delta (FA6), and upper braid-delta front (FA7). The 20 meters of braidplain-to-delta transition strata are largely similar to those of fluvial middle member sections, containing approximately 2% mudstone, unimodal north-northwest paleoflow, and vertical, downstream, and downstream-lateral accretion elements representing compound barforms and channel fills. Above, each braid-delta facies association (FA5–7) preserves high-sinuosity paleocurrent indicators, 6–12% mudstone, and symmetrical, wave-formed sand waves. Decimeter-thick fluid-mud deposits found chiefly in FA6 and less commonly in FA7 indicate the presence of a turbidity-maximum zone that records brackish-water conditions in the distal braid delta. Trace fossils concentrated in FA7 suggest that metazoans were confined to the upper braid-delta front and could not tolerate the variable salinity of the braid delta. Increased marine influence with stratigraphic height requires gradual transgression during deposition of the middle member of the Wood Canyon Formation, possibly as part of a lowstand systems tract.

中文翻译：

---

河流主导，波浪和潮汐影响的植被前辫状河三角洲的建筑：美国加利福尼亚南部大理石山的伍德峡谷地层的寒武纪中层成员

在加利福尼亚东南部的莫哈韦沙漠中，伍德峡谷地层的寒武纪中层成员的露头保存了植被前的辫状河流和辫状三角洲环境的沉积物。通过详细的地层测井，相分析，基于“运动构造”模型的建筑板块以及一套古流和积积表面测量值，在大理石山南部的一个78米厚的断面进行了记录。在大陆范围的辫状平原的末端开发了一个以河为主，受波浪和潮汐影响的辫状三角洲。与其他之前泥盆纪辫状-三角洲地层基本不存在泥岩相比，中层体系的大部分包含了5％以上的泥岩。四个相协会，FA4-7，构成中间部分，并（按地层高度顺序）代表辫状平原到三角洲的过渡带（FA4），近端辫状三角洲（FA5），远端辫状三角洲（FA6）和上部辫状三角洲前缘（FA7）。辫状平原到三角洲的20米过渡层与河流中段的过渡层大体相似，包含约2％的泥岩，单峰的西北西北古流以及代表复合条形和河道的垂直，下游和下游侧增生元素填充。在上方，每个辫状-三角洲相（FA5-7）都保留了高弯度的古流指示剂，6-12％的泥岩以及对称的波浪状砂波。主要在FA6中发现的，只有几米厚的流体泥浆沉积物，而在FA7中很少见，这表明存在最大浊度区，该最大浊度区记录了远端辫状河三角洲的微咸水状况。痕量化石集中在FA7中，表明后生动物被限制在上辫状三角洲的前部，不能容忍辫状三角洲的盐度变化。随着地层高度的增加，海洋影响要求在伍德峡谷地层中段沉积过程中逐渐侵入，这可能是低位系统道的一部分。