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首页> 外文期刊>Cretaceous Research >Mapping the rise and demise of Urgonian platforms (Late Hauterivian - Early Aptian) in southeastern France and the Swiss Jura
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Mapping the rise and demise of Urgonian platforms (Late Hauterivian - Early Aptian) in southeastern France and the Swiss Jura

机译：绘制法国东南部和瑞士汝拉州Urgonian平台（晚期上特夫阶-阿普特晚期）的兴起和消亡的地图

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摘要

Lower Cretaceous carbonate deposits historically called " Urgonian limestones" are widely exposed around the margins of the Vocontian basin in southeastern France and in the adjacent Swiss Jura. This paper presents the history of their rise, growth and sudden demise. Eleven maps were constructed for deposits ranging in age from the Late Hauterivian pro parte to the Early Aptian (Bedoulian) pro parte. Based on sequential interpretations, they illustrate the present geographical distribution of the inner platform facies (Urgonian limestones stricto sensu, with rudists), the outer platform facies (essentially bioclastic deposits) and the basinal facies (slope, hemipelagic, pelagic deposits). These maps depict only the final terms of each successive sequence (the late highstand intervals). Chronostratigraphy is constrained by ammonites found mainly in basinal deposits, by echinoids, by rudists and to a lesser extent by dinoflagellates and calcareous nannoplancton. Inner platform, outer platform and slope (talus) deposits are dated by rich assemblages of orbitolinids and dasycladalean algae. Currently 39 species of orbitolinids have been recognized and their ranges collated with those of the ammonites in the area.In the Jura and in Provence the oldest Urgonian deposits are dated early Late Hauterivian, thus showing the synchroneity of the onset of platform carbonates development on both the southern and northern margins of the basin. Thereafter, growth of the platforms led a clearly regressive shallowing-upward trend, resulting from a stepwise progradation toward the center of the Vocontian area, coordinated with cyclical exposures in the inner platform areas. The maximum reduction of the platform deposits occurred early in Late Barremian times, coeval with a noticeable turnover in the orbitolinids assemblages.Thereafter, carbonate platform deposition shifted toward the margins of the Vocontian basin. In Early Aptian time, a well-dated discontinuity of regional extent marks the sudden, almost synchronous disappearance of the Urgonian deposits.
机译：历史上被称为“ Urgonian石灰岩”的下白垩统碳酸盐矿床在法国东南部和邻近的瑞士汝拉州Vocontian盆地的周围广泛暴露。本文介绍了它们的崛起，增长和突然灭亡的历史。绘制了11张地图，显示了从上奥特里夫时代晚期到阿普提安早期时代（白俄罗斯）的沉积物。基于序贯解释，他们说明了内部平台相（乌尔冈石灰岩，具有鲁德斯的严格意义），外部平台相（主要是生物碎屑沉积物）和盆地相（坡度，半潜质，浮游沉积）的当前地理分布。这些图仅描绘了每个连续序列的最后一项（后期高潮间隔）。年代地层学受到主要在盆地沉积物中发现的mon石，类chin虫、,虫和小鞭毛虫和钙质纳米浮游生物的限制。内层平台，外层平台和斜坡（距骨）沉积物由丰富的眶类动物和达西克拉达兰藻类组成。目前，已经识别出39种眶类动物，其范围与该地区的铵盐核对。在汝拉州和普罗旺斯，最古老的Urgonian沉积物是晚期Hauterivian年代，因此表明这两个平台上碳酸盐岩发育的同步性。盆地的南部和北部边缘。此后，平台的生长导致明显的回归的浅浅上升趋势，这是由于向Vocontian地区的中心逐步逐步发展，并与内部平台区域的周期性暴露相协调。平台沉积物的最大减少发生在巴里米亚晚期晚期，同时伴随着轨道类动物群的显着周转。此后，碳酸盐台地沉积物向Vocontian盆地边缘转移。在Aptian早期，区域范围的不连续性标志着Urgonian矿床突然，几乎同步消失。

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