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首页> 外文期刊>Facies >The Karsteniceras level: Dysoxic ammonoid beds within the Early Cretaceous (Barremian, Northern Calcareous Alps, Austria)
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The Karsteniceras level: Dysoxic ammonoid beds within the Early Cretaceous (Barremian, Northern Calcareous Alps, Austria)

机译：Karsteniceras水平：早白垩世（巴雷米亚，北钙质阿尔卑斯山，奥地利）内的缺氧性铵盐层

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An Early Cretaceous mass-occurrence of ammonites in the Ternberg Nappe of the Northern Calcareous Alps (Upper Austria) is described for the first time. The mass-occurrence (section KB1-B=Klausrieglerbach 1, section B) dominated by Karsteniceras ternbergense Lukeneder is of Early Barremian age (Moutoniceras moutonianum Zone). The Karsteniceras mass-occurrence comprises eight different genera, each apparently represented by a single species, of which four are identified to species level. About 300 specimens of K. ternbergense between 5 and 37 mm in diameter were investigated. Two groups showing thick main ribs but different maximum size are distinguishable. The latter parameters are suggested to reflect sexual dimorphism within K. ternbergense, a condition that is most probably applicable to the whole leptoceratoid group. The geochemical results indicate that the Karsteniceras mass-occurrence within the described Lower Cretaceous succession was deposited under intermittent oxygen-depleted conditions associated with stable, salinity-stratified water masses. The rhythmicity of laminated black-marly lime-stone layers and light-grey bioturbated, organic-poor lime-stones suggests that the oxic and dysoxic conditions underwent highly dynamic changes. The deposition of the limestones in this interval occurred in an unstable environment and was controlled by short- and long-term fluctuations in oxygen levels. Karsteniceras inhabited areas of stagnant water with low dissolved oxygen; it showed peak abundance during times of oxygen depletion, which partially hindered other invertebrates from settling in such environments. The autochthonous Karsteniceras mass-occurrence can be assigned to the deposition-type of ‘Konservat Lagerstätte’, which is indicated by the preservation of phosphatic siphuncle structures and proved by the in situ preservation of aptychi within Karsteniceras ternbergense. Based on lithological and geochemical analysis combined with in vestigations of trace fossils, microfossils and macrofossils, an invasion of an opportunistic (r-strategist) Karsteniceras biocoenosis during nonfavorable conditions over the sea bed during the Lower Barremian is proposed for the KB1-B section.
机译：首次描述了北部钙质阿尔卑斯山（上奥地利州）的特恩贝格纳普早期白垩纪大量存在的am石。由Karsteniceras ternbergense Lukeneder主导的大量发生（部分KB1-B = Klausrieglerbach 1，部分B）发生在巴雷米亚早期（Moutoniceras moutonianum Zone）。 Karsteniceras大量出现包括八个不同的属，每个属明显地由一个物种代表，其中四个在物种水平上被鉴定。研究了大约300个直径在5到37毫米之间的白僵菌标本。两组显示出较粗的主肋骨，但最大尺寸不同。建议使用后一种参数来反映出花粉虱的性二态性，这种情况最有可能适用于整个瘦小体组。地球化学结果表明，所描述的下白垩纪演替过程中的岩溶质沉积是在间歇性耗氧条件下沉积的，该条件与稳定的盐度分层水团有关。层积的黑灰色石灰岩层和浅灰色的生物扰动的有机贫酸石灰岩层的节奏性表明，在有氧和低氧条件下经历了高度动态变化。在这段时间间隔内，石灰石的沉积发生在不稳定的环境中，并受氧气水平的短期和长期波动的控制。 Karsteniceras居住在积水且溶解氧低的地区；在缺氧期间，它显示出峰值丰度，部分阻碍了其他无脊椎动物在这种环境中的沉降。可以将自生的Karsteniceras大量发生归因于“ KonservatLagerstätte”的沉积类型，这可以通过磷酸性笔触结构的保存来说明，并可以通过在karsteniceras ternbergense中原位保存aptychi来证明。基于岩性和地球化学分析，并结合痕迹化石，微化石和大型化石的遗迹，提出了针对KB1-B剖面下巴里米亚海床不利条件下的机会性（r策略家）Karsteniceras生物群落的入侵。

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