An uncommonly continuous Lower Jurassic (uppermost Sinemurian and Pliensbachian) section (Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, UK) comprises hemipelagic calcareous mudstone, wackestone/siltstone and subordinate packstone/sandstone. Some beds show bigradational grading, and their sedimentary structures are typical of contourite drift facies. On the basis of the long-term persistence and stability of the currents that formed these deposits, sedimentation was likely controlled by thermohaline-driven geostrophic contour currents circulating between the Boreal ocean and Peri-Tethys through the narrow and relatively deep Cardigan Bay Basin (Cardigan Bay Strait). Trace fossils are strongly dominated by Phycosiphon incertum, which was produced by opportunistic colonizers. Thalassinoides, Schaubcylindrichnus and Teichichnus are common, accompanied by less common Zoophycos, Planolites, Palaeophycus, Trichichnus and dwelling structures such as cf. Polykladichnus, Siphonichnus and Skolithos. The ichnofabrics are usually simple, which results from generally high rates of deposition, unstable, water-saturated soft-ground substrate, and the domination of well-adapted Phycosiphon, but there are also cyclic appearances of more complex ichnofabrics with dwelling structures, reflecting more stable bottom conditions. A new detailed analysis of the core has allowed cycles to be distinguished based on combination of ichnological and sedimentological features, pointing to distinct cyclicity of oceanographic mechanisms influenced by orbital forcing and driving the inferred fluctuations in benthic life conditions, controlled mainly by variation in contour current intensity and oxygenation of bottom water reflected by trace fossils. The ichnological cycles show four-order hierarchy, which can be attributed to the orbital cycles: precession and obliquity (4th order), short eccentricity (3rd order), and long eccentricity (2nd order). The longest (~ 2.5 Myr) 1st order cyclicity is attributable to the longer ‟grand orbital cycles” (period related to the Earth–Mars secular resonance), with long-term impacts on palaeoclimatic and oceanic circulation dynamics, and is recorded in large-scale changes in ichnodiversity, correlating with long-term changes of clay minerals and carbonate content. Possibly, there is also ~ 9 Myr cyclicity, expressed in observed modulation of frequency of precession cycles by eccentricity. Harmonic analysis of the cyclicity gives high confidence of orbital signals and allows refined estimation of duration of the Pliensbachian (~8.4 Myr) and the jamesoni (~2.8 Myr), ibex (~ 2.0 Myr), davoei (~ 0.47 Myr), margaritatus (~ 2.33 Myr) and spinatum zones (~ 0.8 Myr) with an overall stable sedimentation rate of 4.5–5.1 cm/kyr. Obtained durations show improved fit between 2nd–4th and 1st order cycle and removes the problem of an anomalously long duration and resulting much lower sedimentation rate for the spinatum Zone, previously obtained by other methods. A higher diversity of trace fossils is noticed in intervals enriched in smectite; most likely, this clay mineral occluded pore spaces and limited the competition from the opportunist Phycosiphon makers, allowing development of other, more specialized forms. The continuous, expanded ichnological record of deep-water hemipelagic/contour drift sediments is sensitive to climatic and oceanographic changes controlled by orbital cycles. The Cardigan Bay Strait played an important role in the Early Jurassic (at least Pliensbachian) oceanic circulation, providing a major link between the northern and southern part of the Laurasian Seaway (and in general between the Boreal and Peri-Tethys domains), funneling currents flowing from the north to the south.

一个罕见的连续下侏罗统（最上层 Sinemurian 和 Pliensbachian）部分（Llanbedr（Mochras Farm）Borehole，Cardigan Bay Basin，UK）包括半远洋钙质泥岩、泥灰岩/粉砂岩和次要的泥灰岩/砂岩。部分床层呈双级配，沉积构造具有典型的等高岩漂移相。基于形成这些沉积物的洋流的长期持续性和稳定性，沉积作用可能受温盐驱动的地转等高流控制，该洋流在北方洋和特提斯半岛之间循环通过狭窄且相对较深的卡迪根湾盆地（Cardigan Bay Basin湾海峡）。痕量化石强烈地被Phycosiphon incertum支配，它是由机会主义的殖民者产生的。海藻，Schaubcylindrichnus和Teichichnus是常见的，并伴有较少见Zoophycos，Planolites，Palaeophycus，Trichichnus和住宅结构，例如参见 Polykladichnus，Siphonichnus和Skolithos。地层织物通常很简单，这是由于通常的高沉积率、不稳定的、水饱和的软地面基材以及适应性强的 Phycosiphon占主导地位，但也有更复杂的带有住宅结构的异形织物的循环出现，反映了更稳定的底部条件。对岩心的新详细分析使得可以根据地质学和沉积学特征的组合来区分循环，指出受轨道强迫影响的海洋学机制的明显周期性，并驱动主要受等高流变化控制的底栖生物条件的推断波动微量化石反映的底层水的强度和氧化。周期显示四阶层次，这可以归因于轨道周期：进动和倾角（4阶），短偏心率（3阶）和长偏心率（2阶）。最长的 (~ 2. 5 Myr) 一阶循环归因于更长的“大轨道周期”（与地球-火星长期共振相关的周期），对古气候和海洋环流动力学有长期影响，并记录在鱼类多样性的大规模变化中，与粘土矿物和碳酸盐含量的长期变化相关。可能还有 ~ 9 Myr 的周期性，用偏心率对进动周期频率的观察调制表示。周期的谐波分析给出了轨道信号的高置信度，并允许精确估计 Pliensbachian (~8.4 Myr) 的持续时间和 与粘土矿物和碳酸盐含量的长期变化相关。可能还有 ~ 9 Myr 的周期性，用偏心率对进动周期频率的观察调制表示。周期的谐波分析给出了轨道信号的高置信度，并允许精确估计 Pliensbachian (~8.4 Myr) 的持续时间和 与粘土矿物和碳酸盐含量的长期变化相关。可能还有 ~ 9 Myr 的周期性，用偏心率对进动周期频率的观察调制表示。周期的谐波分析给出了轨道信号的高置信度，并允许精确估计 Pliensbachian (~8.4 Myr) 的持续时间和jamesoni ( ~ 2.8 Myr)、ibex (~ 2.0 Myr)、davoe i (~ 0.47 Myr)、margaritatus (~ 2.33 Myr) 和Spinatum区 (~ 0.8 Myr) 的总体稳定沉降率为 4.5–5.1 cm/kyr。获得的持续时间显示出 2 至 4 阶和 1 阶循环之间的拟合得到改善，并消除了异常长的持续时间以及导致之前通过其他方法获得的棘状区沉降率低得多的问题。在富含蒙脱石的区间中发现了更高多样性的痕量化石；最有可能的是，这种粘土矿物封闭了孔隙空间并限制了机会主义者Phycosiphon的竞争制造商，允许开发其他更专业的形式。深水半远洋/等高漂流沉积物的连续、扩展的地质记录对受轨道周期控制的气候和海洋变化很敏感。卡迪根湾海峡在早侏罗世（至少普连斯巴阶）海洋环流中发挥了重要作用，提供了劳亚斯海道北部和南部之间（以及北方和特提斯附近地区之间的主要联系）的主要联系，汇集了洋流从北流向南。