Stratigraphic distribution patterns of particulate organic matter (POM) have been widely used for facies recognition and paleoenvironmental interpretation as well as to decipher proximal to distal trends within fine-grained sediments. The Lower Cretaceous mudstone-dominated succession in the eastern Lower Saxony Basin (LSB) offers an excellent opportunity to critically evaluate such palynofacies parameters, commonly used to identify transgressive-regressive (T-R) cycles in marine sediments. For the seemingly monotonous succession, a robust sequence stratigraphic framework has been previously established by integrating high-resolution elemental intensity data from X-Ray Fluorescence (XRF) core scanning and biostratigraphy from four drill cores. In this study, the composition and distribution of the POM has been assessed by analysis of 220 strew mounts using transmitted-light microscopy. Overall, the POM composition indicates deposition in a mud-dominated proximal to distal shelf setting. The ratio of opaque versus translucent phytoclasts (OP/TR ratio) shows a distinct long-term increase from the Berriasian onwards with maximum values during the early Hauterivian, followed by a subsequent decrease in OP/TR ratio. This trend broadly reflects the overall T-R evolution of the succession interpreted from Si/Al changes. This also applies to the size and sorting of opaque phytoclasts, with the greatest amplitude changes in opaque particle size parameters being observed in the more proximal deposits of the studied succession. On the other hand, the ratio of terrestrial versus marine palynomorphs (T/M ratio), often applied as indicator of proximal to distal trends and distances from the coastline, shows no correlation with the T-R cycles. Systematic long- and short-term trends visible in T/M ratio correspond to variations in the XRF-derived Ca/Ti stratigraphic trend, which is interpreted to reflect variations in carbonate content. This may indicate that the T/M ratio in the LSB is largely controlled by variations in marine palynomorph flux, probably related to productivity changes of the organic-walled microplankton.

中文翻译：

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古岩相作为早白垩世海洋泥岩中对海平面敏感的代理 – 一项关键评估


颗粒有机物 （POM） 的地层分布模式已广泛用于相识别和古环境解释，以及破译细粒沉积物中近端到远端的趋势。下萨克森盆地东部 （LSB） 以下白垩纪泥岩为主的演替为批判性评估此类古岩相参数提供了绝佳的机会，这些参数通常用于识别海洋沉积物中的海侵-回归 （T-R） 循环。对于看似单调的演替，先前已经通过整合来自 X 射线荧光 （XRF） 岩芯扫描的高分辨率元素强度数据和来自四个钻芯的生物地层学建立了一个强大的层序地层学框架。在这项研究中，通过使用透射光显微镜对 220 个散落的支架进行分析，评估了 POM 的组成和分布。总体而言，POM 成分表明沉积在以泥为主的近端至远端大陆架环境中。不透明与半透明植物碎屑的比率 （OP/TR 比率） 显示从 Berriasian 开始明显的长期增加，在 Hauterivian 早期达到最大值，随后 OP/TR 比率下降。这一趋势大致反映了从 Si/Al 变化解释的演替的整体 T-R 演变。这也适用于不透明植物碎屑的大小和排序，在所研究的演替的更近端的沉积物中观察到不透明粒径参数的最大振幅变化。另一方面，陆地与海洋 palynomorphs 的比率 （T/M ratio） 通常用作近端到远端趋势和与海岸线距离的指标，与 T-R 周期没有相关性。 以 T/M 比值可见的系统性长期和短期趋势对应于 XRF 衍生的 Ca/Ti 地层趋势的变化，该趋势被解释为反映了碳酸盐含量的变化。这可能表明 LSB 中的 T/M 比在很大程度上受海洋 palynomorph 通量变化的控制，这可能与有机壁微浮游生物的生产力变化有关。