Abstract. High resolution clay mineral and stable isotope (C, O) data are reported from the upper Sinemurian (Lower Jurassic) of the Cardigan Bay Basin (Llanbedr [Mochras Farm] borehole, northwest Wales) and the Paris Basin (Montcornet borehole, northern France) to highlight the prevailing environmental and climatic conditions. In both basins, located at similar palaeolatitudes of 30–35° N, the clay mineral assemblages comprise chlorite, illite, illite-smectite mixed-layers (R1 I-S), smectite and kaolinite in various proportions. Because the influence of burial diagenesis and authigenesis is negligible in both boreholes, the clay minerals are interpreted to be derived from the erosion of the Caledonian and Variscan massifs, including their basement and pedogenic cover. In the Cardigan Bay Basin, the variations in the proportions of smectite and kaolinite are inversely related to each other over the entire upper Sinemurian succession. As in the Pliensbachian, the stratigraphical distribution reveals an alternation of kaolinite-rich intervals reflecting strong hydrolysing conditions, and smectite-rich intervals indicating a semi-arid climate. Kaolinite is particularly abundant in the upper part of the obtusum Zone and in the oxynotum Zone, suggesting more intense hydrolysing conditions likely coeval with warm conditions responsible for an acceleration of the hydrological cycle. This interval is also marked by a negative excursion of δ¹³C_carb and δ¹⁸O_carb, which may confirm a warmer palaeoclimate, although these excursions may be exaggerated or overprinted by the carbonate diagenesis. In the north of the Paris Basin, the stratigraphical succession is much thinner compared to the Cardigan Bay Basin site, and the oxynotum Zone is either absent or highly condensed. The clay assemblages are dominantly composed of illite and kaolinite without significant stratigraphical trends, but a smectite-rich interval identified in the obtusum Zone is interpreted as a consequence of the emersion of the London-Brabant Massif following a lowering of sea-level. A long-term decrease of δ¹³C_org from the late oxynotum/early raricostatum zones is also recorded in the two sites and may precede or partly include the negative carbon-isotope excursion of the Sinemurian/Pliensbachian Boundary Event, recognised in most basins worldwide, and interpreted as a late pulse of the Central Atlantic Magmatic Province volcanism.

中文翻译：

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侏罗纪早期（晚西内穆里，Laurasian航道）的中纬度气候模式，将暖湿和半干旱时期的百万年尺度变化

摘要。从Cardigan湾盆地（威尔士西北部的Llanbedr [Mochras Farm]井眼）和巴黎盆地（法国北部的Montcornet井眼）的上Sinemurian（下侏罗纪）上部高分辨率粘土矿物和稳定同位素（C，O）数据中进行了报道。强调当前的环境和气候条件。在这两个盆地中，它们位于类似的北纬30-35°的古纬度上，粘土矿物组合包括绿泥石，伊利石，伊利石-蒙脱石混合层（R1 IS），绿土和高岭石。由于在两个钻孔中埋藏成岩作用和自生作用的影响都可以忽略不计，因此粘土矿物被解释为来自加里东和瓦里斯坎地块的侵蚀，包括它们的基底和成岩作用。在Cardigan湾盆地，在整个上Sinemurian演替过程中，蒙脱石和高岭石的比例变化彼此成反比。与普林斯巴赫（Pliensbachian）一样，地层分布显示出富高岭石层段的交替，反映了强烈的水解条件，而富蒙皂石层段则表明存在半干旱气候。高岭石的上部特别丰富obtusum区，在oxynotum区，这表明更强烈的水解条件与负责水文循环的加速温暖的环境下可能同时代。此时间间隔也由δ的负偏移标记¹³ Ç_{碳水化合物}和δ ¹⁸ ö_{碳水化合物}，其可以确认较暖的古气候，虽然这些偏移可能被夸大或由碳酸盐成岩套印。在巴黎盆地北部，与卡迪根湾盆地遗址和含氧土层相比，地层演替要薄得多。区域不存在或高度集中。黏土组合物主要由伊利石和高岭石组成，没有明显的地层趋势，但是在tus带中发现的富含绿土的区间被解释为伦敦-布拉邦地块出现后海平面下降的结果。δ的长期下降¹³ Ç_组织从晚oxynotum /早raricostatum区也被记录在两个地点和可能先于或部分包括辛涅缪尔/ Pliensbachian边界事件的负碳同位素漂移，在大多数盆地世界公认，并被解释为中大西洋岩浆省火山活动的晚期。