Bryozoan–stromatolite associations (bryostromatolites) formed conspicuous reef structures throughout the Sheinwoodian (Wenlock) to Ludfordian (Ludlow) stratigraphy on Gotland but have not been described so far. They are mainly composed of encrusting bryozoans forming a complex intergrowth with porostromate and spongiostromate microbes and are different from the abundant stromatoporoid–coral–algal reefs with respect to their composition. In the bryostromatolite different growth stages can be identified. The observed succession can be taken as evidence for cyclic environmental changes during reef formation. Stenohaline reef-dwelling organisms, such as echinoderms, sponges, corals and trilobites, indicate fully marine salinities. Ten localities exposing bryostromatolites were discovered. Individual bryostromatolites are small with few decimetres up to one metre in size, and occur solely in shallow marine areas. Common features of these reefs on Gotland are cauliflower-like growth, a high bryozoan diversity, a high abundance of phosphatic fossils and components such as bryozoan pearls and inarticulate phosphatic brachiopods, enhanced bioerosion, Palaeomicrocodium crusts, vadose silt and gypsum pseudomorphs. The high abundance of Palaeomicrocodium, as well as the alternation with other crust-forming contributors, suggest that it could have been formed directly at the palaeo-sea surface, probably in times of minor but high-frequency sea-level fluctuations. Vadose silt and pseudomorphs after gypsum in reef cavities indicate subaerial exposure shortly after reef growth. The high amount of phosphatic components indicates a high nutrient input, probably by dust. All bryostromatolites were formed in times of strongly elevated δ¹³C values. The unusual combination of sedimentological and palaeoecological features, as well as their occurrence exclusively during strong positive δ¹³C excursions, are evidence that the bryostromatolite development responded to climatic/oceanographic changes, which may have played an important role in reef control.

中文翻译：

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来自哥特兰岛志留系的富含苔藓虫的叠层石（苔藓叠层石）及其与全球碳循环的气候相关扰动的关系

苔藓虫-叠层石组合（苔藓叠层石）在哥特兰岛的整个 Sheinwoodian (Wenlock) 到 Ludfordian (Ludlow) 地层中形成了显眼的珊瑚礁结构，但迄今为止尚未被描述。它们主要由结壳的苔藓虫组成，与多孔基质和海绵基质微生物形成复杂的共生关系，并且在组成方面与丰富的层孔-珊瑚-藻礁不同。在苔藓叠层石中可以确定不同的生长阶段。观察到的演替可以作为生物礁形成过程中周期性环境变化的证据。栖息于狭盐性珊瑚礁的生物，如棘皮动物、海绵、珊瑚和三叶虫，表明完全是海洋盐度。发现了 10 个暴露苔藓叠层石的地点。单个苔藓叠层石很小，只有几分米，最大可达一米，仅出现​​在浅海区域。哥特兰岛上这些珊瑚礁的共同特征是花椰菜状生长、苔藓动物多样性高、磷酸盐化石和成分丰富，如苔藓动物珍珠和无关节的磷酸盐腕足动物、增强的生物侵蚀、古微球壳、包气淤泥和石膏假形体。古微藻的丰度高，以及与其他地壳形成贡献者的交替，表明它可能直接在古海表面形成，可能是在海平面轻微但高频波动的时期。珊瑚礁洞穴中石膏后的渗流淤泥和假晶质表明珊瑚礁生长后不久就暴露在地下。大量的磷酸盐成分表明高营养输入，可能是由于灰尘。所有苔藓叠层石都是在δ ¹³ C 值强烈升高的时期形成的。沉积学和古生态学特征的不寻常组合，以及它们仅出现在强正δ ¹³期间C 偏移是苔藓叠层石发育对气候/海洋变化做出反应的证据，这可能在珊瑚礁控制中发挥了重要作用。