Bedrock sculpturing of semilithified St. George Formation sandy mudstone exposed on a wave‐cut platform has produced a variety of erosional forms that include surface scratches made by beach debris, ripple‐like ridges that reflect differential erosion of bedrock, potholes, and scallop‐shaped pockets and grooves, which may be straight or sinuous. Straight grooves form by preferential incision of regional joints. Sinuous grooves are not fracture controlled, are oriented parallel to wave run‐up (orthogonal to the coast), and exist as closely spaced subparallel, nonconnecting, internally drained grooves that are best developed on higher platform ramparts and benches. Sinuous grooves have a mean length of 258 cm, mean maximum width of 14 cm, and mean width/length ratio of 0.08. They are not as deeply incised as straight grooves, do not serve as conduits for low‐tide runoff during winter months, and typically terminate by shallowing and narrowing in both seaward and landward directions. Sinuous appearance results from trains of linked comma‐shaped depressions, commonly with the blunt, highly curved end of each being most deeply incised and oriented seaward. Corrasion of bedrock highs and/or cavitation associated with turbulent vortices during tsunami run‐up likely contributed to the genesis and/or enlargement of the sinuous grooves. Auguring and coring in a back barrier bog and diatom analysis reveals a landward‐thinning, ∼17 cm‐thick, laterally continuous, clean, tsunami‐emplaced sand layer with a sharp basal contact up to 125 m inland of the modern high‐tide line. While seasonal cycles of beach aggradation and degradation combined with sediment transport and bedrock erosion accompanying low‐tide runoff and high‐tide wave motion undoubtedly accounts for form modification of sinuous grooves, it is unlikely to account for their origin.

中文翻译：

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加利福尼亚州新月市地区圆石滩波浪切割平台的海啸（？）雕塑

半岩化圣乔治组砂质泥岩在波浪切割平台上的基岩雕刻产生了多种侵蚀形式，包括海滩碎片造成的表面划痕、反映基岩差异侵蚀的波纹状山脊、坑洼和扇贝形口袋和凹槽，可能是直的或弯曲的。通过优先切割区域关节形成直槽。蜿蜒的凹槽不受裂缝控制，平行于波浪爬高（与海岸正交），并且以紧密间隔的、非连接的、内部排水的凹槽形式存在，最好在较高的平台壁垒和长凳上开发。蜿蜒凹槽的平均长度为 258 厘米，平均最大宽度为 14 厘米，平均宽度/长度比为 0.08。它们不像直槽那么深，在冬季月份不作为低潮径流的管道，并且通常以向海和向陆方向变浅和变窄而终止。蜿蜒的外观是由一连串相连的逗号形凹陷造成的，通常每个凹陷的钝、高度弯曲的末端切得最深，面向大海。海啸上升期间与湍流涡旋相关的基岩高点的腐蚀和/或空化可能导致了蜿蜒凹槽的形成和/或扩大。在后障沼泽和硅藻分析中的测量和取芯揭示了一个向陆地变薄、约 17 cm 厚、横向连续、清洁、海啸席位的沙层，与现代高潮线内陆高达 125 m 的尖锐基底接触.