Geological mapping reveals the role of Early Jurassic rift architecture in the dispersal of calciturbidites: new insights from the Central and Northern Apennines

A geological mapping project was performed in three sectors of the Umbria-Marche Apennines (Central Italy): the Narni-Amelia, Sabini, and Sibillini (Mt Pennino) Mountain Ridges. One of the outcomes of this project is the improvement of our database of the occurrence of levels or stratigraphic intervals with resedimented shallow-water carbonate material in the Jurassic part of the succession. The Umbria-Marche region was characterised by an exceedingly complex pattern of intrabasinal highs (pelagic carbonate platforms) and intervening basins in the Jurassic. Due to this, a map pairing the occurrences of such resedimented beds with an updated palaeogeography becomes the natural descriptor of how the rift-related submarine topography (an extreme instance of it) could influence the dispersal of materials sourced by coeval active carbonate factories. Resedimented shallow-water carbonates were discovered and mapped for the first time in the study areas, embedded in uppermost Lower to Upper Jurassic cherty pelagites.While calciturbidites of this age are not unexpected in the Sabina and Narni-Amelia sectors, lying in the neighborhood of the productive Lazio-Abruzzo Carbonate Platform, their occurrence in settings far removed from any obvious shallow-water source is puzzling, since intrabasinal highs in the Umbria-Marche Apennines had all drowned by the early Pliensbachian. The Lazio-Abruzzo Carbonate Platform is the most likely source-area for ooidal/peloidal/bioclastic calciturbidites of both the Narni-Amelia and the Sabina sectors (~50 km away from the present-day margins of the carbonate platform), while occurrences in the northern part of the Sibillini Mts (~100 km away from those margins) might require alternative sources. Geological mapping shows that the marginal palaeoescarpments of pelagic carbonate platforms formed obstacles to the gravity flows as sediment load was discharged at their toes. While turbidity flows were locally vigorous enough to climb the escarpments, leaving overbank deposits on the pelagic carbonate platform-tops, a “shelter” effect is evidenced by the resediment-free nature of those basins lying downflow, which had to be shielded by pelagic carbonate platforms.
Attached in this data are the raw field photographs of the analysed outcrops, clear of the line-drawing layer.

在意大利中部乌尔比诺-马尔凯阿彭宁山脉的三个区域——纳尔尼-阿梅利亚、萨比尼和西比尔尼（彭尼诺山脊）进行了地质制图项目。该项目的一项成果是提升了我们对白垩纪地层中沉积浅水碳酸盐物质出现层位或地层间隔的数据库。马尔凯-乌尔比诺地区在侏罗纪时期呈现出极其复杂的盆地内隆起（远洋碳酸盐平台）与相邻盆地的分布格局。因此，将此类再沉积层的出现与更新的古地理学相结合的地图，自然成为描述裂谷相关海底地形（一种极端情况）如何影响同期活跃碳酸盐工厂所产生物质扩散的天然描述符。研究区域内首次发现并制图了再沉积的浅水碳酸盐，它们嵌入在上侏罗统最上部的硅质远洋沉积物中。尽管这一时期在萨比尼和纳尔尼-阿梅利亚地区（位于生产性拉齐奥-阿布鲁佐碳酸盐平台附近）的钙质浊流并不意外，但它们出现在远离任何明显浅水来源的环境中则令人费解，因为乌尔比诺-马尔凯阿彭宁山脉的盆地内隆起在早皮灵萨克阶时已全部淹没。拉齐奥-阿布鲁佐碳酸盐平台可能是纳尔尼-阿梅利亚和萨比尼地区卵石/圆球/生物碎屑钙质浊流的可能来源区（距离碳酸盐平台现今边缘约50公里），而西比尔尼山脉北部（距离那些边缘约100公里）的出现可能需要其他来源。地质制图表明，远洋碳酸盐平台的边缘古地形对重力流构成了障碍，因为沉积负荷在它们脚下的释放。尽管浊流在局部地区足够强大，可以爬上陡坡，并在远洋碳酸盐平台顶部留下溢出沉积物，但那些下游盆地无再沉积的特性表明了一种“庇护”效应，这些盆地必须由远洋碳酸盐平台所保护。附在本数据集中的是分析露头现场的原始野外照片，照片清晰，无线条绘制层。