We propose a new facies classification scheme of the cyclic lacustrine carbonates of the Bernburg Formation (Lower Triassic, Induan), with a major focus on the microbial biota and grains. Our data are based on a detailed bed-by-bed outcrop study in Central Germany, within a robust (litho)stratigraphic framework. We concentrate on two intervals of the Bernburg Formation: one around the Calvörde/Bernburg Formation boundary (including the HRZ – „Hauptrogensteinzone“), and a second around the ninth cycle near the upper formation boundary. The textural and mineralogical composition of the two endmember components: skeletal stromatolites and oolites, and the macro-, meso-, and microstructural characteristics (supplemented by μ-XRF-data) allow to classify the carbonates into five lithofacies types. They are interpreted with respect to the development of an ideal lacustrine depositional cycle, embedded between a lake level rise and a lake level fall. The microfacies attributes of the microbialites include various lamination types, shrubs, spherulites, and laminated/clotted/fenestral microfabrics. All sedimentologic (macro-, meso, and microscale) and geochemical data of this study indicate nearshore deposition of the carbonates at marginal shoals in a major endorheic lake (playa lake) with high alkalinity and salinity, and strongly fluctuating lake levels, under arid climates. The lacustrine carbonates are associated with maximum lake expansions, and are laterally interfingering with fan deltas, as indicated by abundant clastic grains in the intercalations of the skeletal stromatolites. The Bernburg Formation microbial buildups reflect changes in lake-level, hydrodynamics and grain supply, and therefore offer insights for the paleoenvironmental interpretation of lacustrine microbialites elsewhere.

中文翻译：

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重新审视 Bernburg 组的下三叠统 (Induan) 叠层石和鲕粒——德国中部湖泊碳酸盐岩的微相和古环境

我们提出了一种新的 Bernburg 组（下三叠统，Induan）环湖碳酸盐岩相分类方案，主要关注微生物群和谷物。我们的数据基于在稳健的（岩相）地层框架内在德国中部进行的详细逐层露头研究。我们专注于 Bernburg 地层的两个层段：一个围绕 Calvörde/Bernburg 地层边界（包括 HRZ –“Hauptrogensteinzone”），第二个围绕着靠近上层边界的第九旋回。两个端元组分的结构和矿物组成：骨架叠层石和鲕粒，以及宏观、中观和微观结构特征（由 μ-XRF 数据补充）允许将碳酸盐分为五种岩相类型。它们被解释为理想的湖泊沉积循环的发展，嵌入在湖水位上升和湖位下降之间。微生物岩的微相属性包括各种层压类型、灌木、球晶和层压/凝块/窗孔微织物。本研究的所有沉积学（宏观、中观和微观尺度）和地球化学数据表明，在干旱气候下，一个主要内陆湖（普拉亚湖）的边缘浅滩的碳酸盐近岸沉积，该湖具有高碱度和高盐度，湖水位波动很大. 湖相碳酸盐岩与最大的湖泊扩张有关，并与扇三角洲横向交错，如骨架叠层石的夹层中丰富的碎屑颗粒所表明的那样。