Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m2 with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw in a Cartesian coordinate system. This method allows an efficient measurement and analysis of the orientation of thousands of specimens and is a major advantage compared to the traditional 2D approach, which measures only the azimuth (yaw) angles. The resulting data can variously be utilized for taphonomic analyses and the reconstruction of prevailing hydrodynamic regimes and depositional environments. For the first time, the influence of possible post-sedimentary vertical displacements can be quantified with high accuracy. Here, the effect of nearby fault lines-present in the reef-was tested on strongly tilted oyster shells, but it was found out that the fault lines did not have a statistically significant effect on the large tilt angles. Aside from the high reproducibility, a further advantage of the method is its non-destructive nature, which is especially suitable for geoparks and protected sites such as the studied shell bed.

中文翻译：

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从密集的中新世贝壳床上自动确定化石牡蛎贝壳的3D方向。

壳床代表了有关导致沉积条件的各种物理过程的有用信息来源。我们提出了一种自动方法来计算沉积层理平面上大量细长和板状物体（僵化的牡蛎壳）的3D方向，旨在支持对可能的沉积模式、,陷或局部断层影响的解释。这项研究的重点是在密堆积的中新世贝壳层中暴露的1900多个化石牡蛎贝壳。通过地面激光扫描在459平方米的区域上以1毫米的分辨率获取3D数据。双壳贝壳被手动定义为数字表面模型的3D点云，并存储在ArcGIS数据库中。每个壳体实际上都嵌入了一个单独的壳体坐标系（ISCS），并且相对于整个构造倾斜的壳体床的坐标系确定了它的方向。方向由笛卡尔坐标系中的旋转角滚动，俯仰和偏航描述。与仅测量方位角（偏航角）的传统2D方法相比，该方法可以有效地测量和分析成千上万个样品的方向，并且是一个主要优势。所得数据可以不同地用于垂体分析和重建主要的水动力区和沉积环境。首次可以高精度地量化可能的沉积后垂直位移的影响。这里，在强烈倾斜的牡蛎壳上测试了礁石附近存在的断层线的影响，但发现断层线对大倾斜角没有统计学上的显着影响。除了具有高重现性之外，该方法的另一个优点是它的无损性质，特别适合于地质公园和受保护的地点，例如研究的贝壳床。