{"title":"Lorette洞穴(Rochefort,比利时)地层学:“gours suspendus”剖面的研究","authors":"Y. Quinif, M. Legros","doi":"10.20341/gb.2021.005","DOIUrl":null,"url":null,"abstract":"The Lorette Cave contains a wide variety of deposits within various stratigraphical contexts. This cave is a part of the complex underground meander cut-off of the Wamme and Lomme rivers, between some swallow-holes along their two talwegs near On, Jemelle and Rochefort, and the general resurgence at Eprave. The Lorette Cave is embedded within the Givetian limestone formations of the Calestienne. This cave displays the first part with a labyrinthic structure. Some parts of the cave galleries are affected by recent tectonic activity, which dislocates some galleries and provokes collapses. The second part of the cave comprises the West Gallery, which contains the most complete sedimentary series. The “gours suspendus” (hanging gours) section is located at the western end of the gallery.\nThe cave contains numerous and rich detrital deposits. The oldest sedimentary unit is a diamictite found in several galleries (e.g. Galerie Fontaine-Bagdad, Salle du Cataclysme). It is composed of large decametric-sized quartz and sandstone pebbles coming from the erosion of the Lower Devonian formations of the Ardenne. This deposit is older than the U/Th dating limit, i.e. 350 ka. The West Gallery exposes an area of collapsed blocks and ends in a vast room. This gallery is filled with a thick fluvial series of upper Pleistocene age and capped by speleothems of Tardiglacial to Holocene age. The large terminal chamber is clogged by flooded pits. A tributary gallery shows a sedimentary series in a subsiding pit, the “Fosse aux Lions” (Lions’ Pit). These deposits are interstratified diamictite interbedded between two fluvial units, the upper part of which displays oblique stratifications. The dating of a summit stalagmite places this set at 120 ka.\nThe present paper analyses a section made in the southern flank of the terminal room, close to the junction with the West Gallery: the “gours suspendus” section. A large part of this section consists of a complex fluvial deposit disconformably resting on top of a compact lower clay formation. This fluvial deposit is stratified, comprising mostly diamictites interstratified with thin levels of gravel and clay. It is capped by an upper clay unit and sealed by a flowstone. Thin strata of finer-grained size sediments (coarse sand), as well as clay lenses, occur within the lower clay.\nThe diamictites indicate a torrential origin of the sediment. At the base, just above the lower clay, some sandy channelling strata testify that one or several fluvial deposition episodes occurred. Then, torrential and probably very short-living events are separated by decantation phases. The pebbles and smaller particles are made of quartz, sandstone and muscovite that most probably originated in the Lower Devonian formations.\nThe “gours suspendus” section provides a new illustration of the succession of sedimentation and erosion phases in Belgian caves. It is now well demonstrated that speleothems grow mainly during temperate to hot and humid climatic phases and detrital infills are deposited in caves during cold/glacial phases. The physical erosion of sediments with ravine formations should be placed in the climatic history of the region. A gullying by a coarse detrital formation like that of the new section is due to a powerful heavy loaded current. The deposits within caves were therefore available, which can only occur during a cold phase due to the absence of continuous vegetation cover. The sand and clay levels interstratified between levels of pebbles indicate nevertheless distinguished flow regimes. However, this torrential lava in the new section seems different from the old diamictite. The deposition of the sedimentary units in the West Gallery seemingly happened during a glacial–interglacial transition. This sedimentological study sets a future perspective for dating flowstones and stalagmites at the top of or embedded within the deposit levels in order to propose a more robust chronological frame for the evolution dynamics of the cave infilling of the Lorette Cave in relation to the climatic history of the region.","PeriodicalId":12812,"journal":{"name":"Geologica Belgica","volume":"31 1","pages":""},"PeriodicalIF":1.2000,"publicationDate":"2021-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Stratigraphy of the Lorette Cave (Rochefort, Belgium): Study of the “gours suspendus” section\",\"authors\":\"Y. Quinif, M. Legros\",\"doi\":\"10.20341/gb.2021.005\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The Lorette Cave contains a wide variety of deposits within various stratigraphical contexts. This cave is a part of the complex underground meander cut-off of the Wamme and Lomme rivers, between some swallow-holes along their two talwegs near On, Jemelle and Rochefort, and the general resurgence at Eprave. The Lorette Cave is embedded within the Givetian limestone formations of the Calestienne. This cave displays the first part with a labyrinthic structure. Some parts of the cave galleries are affected by recent tectonic activity, which dislocates some galleries and provokes collapses. The second part of the cave comprises the West Gallery, which contains the most complete sedimentary series. The “gours suspendus” (hanging gours) section is located at the western end of the gallery.\\nThe cave contains numerous and rich detrital deposits. The oldest sedimentary unit is a diamictite found in several galleries (e.g. Galerie Fontaine-Bagdad, Salle du Cataclysme). It is composed of large decametric-sized quartz and sandstone pebbles coming from the erosion of the Lower Devonian formations of the Ardenne. This deposit is older than the U/Th dating limit, i.e. 350 ka. The West Gallery exposes an area of collapsed blocks and ends in a vast room. This gallery is filled with a thick fluvial series of upper Pleistocene age and capped by speleothems of Tardiglacial to Holocene age. The large terminal chamber is clogged by flooded pits. A tributary gallery shows a sedimentary series in a subsiding pit, the “Fosse aux Lions” (Lions’ Pit). These deposits are interstratified diamictite interbedded between two fluvial units, the upper part of which displays oblique stratifications. The dating of a summit stalagmite places this set at 120 ka.\\nThe present paper analyses a section made in the southern flank of the terminal room, close to the junction with the West Gallery: the “gours suspendus” section. A large part of this section consists of a complex fluvial deposit disconformably resting on top of a compact lower clay formation. This fluvial deposit is stratified, comprising mostly diamictites interstratified with thin levels of gravel and clay. It is capped by an upper clay unit and sealed by a flowstone. Thin strata of finer-grained size sediments (coarse sand), as well as clay lenses, occur within the lower clay.\\nThe diamictites indicate a torrential origin of the sediment. At the base, just above the lower clay, some sandy channelling strata testify that one or several fluvial deposition episodes occurred. Then, torrential and probably very short-living events are separated by decantation phases. The pebbles and smaller particles are made of quartz, sandstone and muscovite that most probably originated in the Lower Devonian formations.\\nThe “gours suspendus” section provides a new illustration of the succession of sedimentation and erosion phases in Belgian caves. It is now well demonstrated that speleothems grow mainly during temperate to hot and humid climatic phases and detrital infills are deposited in caves during cold/glacial phases. The physical erosion of sediments with ravine formations should be placed in the climatic history of the region. A gullying by a coarse detrital formation like that of the new section is due to a powerful heavy loaded current. The deposits within caves were therefore available, which can only occur during a cold phase due to the absence of continuous vegetation cover. The sand and clay levels interstratified between levels of pebbles indicate nevertheless distinguished flow regimes. However, this torrential lava in the new section seems different from the old diamictite. The deposition of the sedimentary units in the West Gallery seemingly happened during a glacial–interglacial transition. This sedimentological study sets a future perspective for dating flowstones and stalagmites at the top of or embedded within the deposit levels in order to propose a more robust chronological frame for the evolution dynamics of the cave infilling of the Lorette Cave in relation to the climatic history of the region.\",\"PeriodicalId\":12812,\"journal\":{\"name\":\"Geologica Belgica\",\"volume\":\"31 1\",\"pages\":\"\"},\"PeriodicalIF\":1.2000,\"publicationDate\":\"2021-12-28\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geologica Belgica\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.20341/gb.2021.005\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geologica Belgica","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.20341/gb.2021.005","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
摘要
洛雷特洞穴在不同的地层背景下包含了各种各样的沉积物。这个洞穴是瓦姆河和洛姆河交界的复杂地下曲流的一部分,位于靠近昂河、耶梅勒河和罗什福尔河的两条支流上的一些燕子洞和埃普拉夫河的普遍回潮之间。洛雷特洞穴嵌在卡莱斯蒂安的吉田石灰岩地层中。这个洞穴展示了迷宫结构的第一部分。洞廊的某些部分受到近期构造活动的影响,使一些洞廊错位并引发崩塌。洞穴的第二部分包括西画廊,其中包含最完整的沉积系列。“挂酒”(gours suspendus)部分位于画廊的西端。洞穴中含有大量丰富的碎屑沉积物。最古老的沉积单元是在几个画廊(如Galerie fontaine - baghdad, Salle du Cataclysme)中发现的二晶岩。它由巨大的十公尺大小的石英和砂岩鹅卵石组成,这些鹅卵石来自阿登山脉下泥盆世地层的侵蚀。该矿床年龄超过U/Th定年极限,即350 ka。西画廊展示了一个倒塌的街区,并在一个巨大的房间结束。这个画廊充满了上更新世时代的厚厚的河流系列,并被缓步期至全新世的洞穴覆盖。大的终端室被淹没的水坑堵塞了。一个支流画廊展示了一个下沉坑中的沉积系列,“狮子坑”(狮子坑)。该矿床为层间杂晶岩,位于两个河流单元之间,河流单元上部呈斜层状。峰顶石笋的年代测定表明,这一组石笋的年代为120ka。本文分析了终点站南侧靠近西画廊连接处的部分:“gours suspension”部分。该剖面的大部分由不整合的复杂河流沉积组成,位于致密的下粘土地层之上。该河流沉积是层状的,主要由层间薄层砾石和粘土组成。它由上部粘土单元覆盖,并由流石密封。细粒度沉积物(粗砂)的薄层,以及粘土透镜,出现在较低的粘土中。二晶岩表明沉积物的起源是剧烈的。在底部,就在较低的粘土之上,一些砂质河道地层证明发生过一次或几次河流沉积。然后,猛烈的事件和可能非常短暂的事件被滗析阶段分开。鹅卵石和更小的颗粒是由石英、砂岩和白云母组成的,它们很可能起源于下泥盆世地层。“gours悬浮”部分为比利时洞穴的沉积和侵蚀阶段的演替提供了新的例证。现在已经充分证明,洞穴石主要生长在温带至湿热气候阶段,而碎屑填充物在寒冷/冰期沉积在洞穴中。具有沟壑形成的沉积物的物理侵蚀应放在该地区的气候历史中。像新剖面那样由粗糙碎屑形成的沟壑是由于强大的重载电流造成的。因此,洞穴内的沉积物是可用的,这只能发生在寒冷的阶段,因为没有连续的植被覆盖。在卵石层之间的沙和粘土层表明了不同的流动状态。然而,在新的部分,这种急流熔岩似乎不同于旧的二晶岩。西画廊沉积单元的沉积似乎发生在冰期-间冰期过渡时期。这项沉积学研究为确定沉积层顶部或嵌入层中的流石和石笋的年代设定了一个未来的视角,以便为Lorette洞穴填充的演化动力学与该地区气候历史的关系提出一个更可靠的时间框架。
Stratigraphy of the Lorette Cave (Rochefort, Belgium): Study of the “gours suspendus” section
The Lorette Cave contains a wide variety of deposits within various stratigraphical contexts. This cave is a part of the complex underground meander cut-off of the Wamme and Lomme rivers, between some swallow-holes along their two talwegs near On, Jemelle and Rochefort, and the general resurgence at Eprave. The Lorette Cave is embedded within the Givetian limestone formations of the Calestienne. This cave displays the first part with a labyrinthic structure. Some parts of the cave galleries are affected by recent tectonic activity, which dislocates some galleries and provokes collapses. The second part of the cave comprises the West Gallery, which contains the most complete sedimentary series. The “gours suspendus” (hanging gours) section is located at the western end of the gallery.
The cave contains numerous and rich detrital deposits. The oldest sedimentary unit is a diamictite found in several galleries (e.g. Galerie Fontaine-Bagdad, Salle du Cataclysme). It is composed of large decametric-sized quartz and sandstone pebbles coming from the erosion of the Lower Devonian formations of the Ardenne. This deposit is older than the U/Th dating limit, i.e. 350 ka. The West Gallery exposes an area of collapsed blocks and ends in a vast room. This gallery is filled with a thick fluvial series of upper Pleistocene age and capped by speleothems of Tardiglacial to Holocene age. The large terminal chamber is clogged by flooded pits. A tributary gallery shows a sedimentary series in a subsiding pit, the “Fosse aux Lions” (Lions’ Pit). These deposits are interstratified diamictite interbedded between two fluvial units, the upper part of which displays oblique stratifications. The dating of a summit stalagmite places this set at 120 ka.
The present paper analyses a section made in the southern flank of the terminal room, close to the junction with the West Gallery: the “gours suspendus” section. A large part of this section consists of a complex fluvial deposit disconformably resting on top of a compact lower clay formation. This fluvial deposit is stratified, comprising mostly diamictites interstratified with thin levels of gravel and clay. It is capped by an upper clay unit and sealed by a flowstone. Thin strata of finer-grained size sediments (coarse sand), as well as clay lenses, occur within the lower clay.
The diamictites indicate a torrential origin of the sediment. At the base, just above the lower clay, some sandy channelling strata testify that one or several fluvial deposition episodes occurred. Then, torrential and probably very short-living events are separated by decantation phases. The pebbles and smaller particles are made of quartz, sandstone and muscovite that most probably originated in the Lower Devonian formations.
The “gours suspendus” section provides a new illustration of the succession of sedimentation and erosion phases in Belgian caves. It is now well demonstrated that speleothems grow mainly during temperate to hot and humid climatic phases and detrital infills are deposited in caves during cold/glacial phases. The physical erosion of sediments with ravine formations should be placed in the climatic history of the region. A gullying by a coarse detrital formation like that of the new section is due to a powerful heavy loaded current. The deposits within caves were therefore available, which can only occur during a cold phase due to the absence of continuous vegetation cover. The sand and clay levels interstratified between levels of pebbles indicate nevertheless distinguished flow regimes. However, this torrential lava in the new section seems different from the old diamictite. The deposition of the sedimentary units in the West Gallery seemingly happened during a glacial–interglacial transition. This sedimentological study sets a future perspective for dating flowstones and stalagmites at the top of or embedded within the deposit levels in order to propose a more robust chronological frame for the evolution dynamics of the cave infilling of the Lorette Cave in relation to the climatic history of the region.
期刊介绍:
Geologica Belgica is a Belgian journal that welcomes papers concerning all aspects of the earth sciences, with a particular emphasis on the regional geology of Belgium, North West Europe and central Africa. Papers not dedicated to the geology of Belgium, North West Europe and central Africa are only accepted when one of the authors is linked to a Belgian University or Institution. Thematic issues are highly appreciated. In this case, guest editors take in charge the selection of the manuscripts and the subject of the papers can be enlarged. The journal is in open access.
Submitted manuscripts should be concise, presenting material not previously published. The journal also encourages the publication of papers from Belgian junior authors. Short letters are accepted. Papers written in English are preferred. Each mansucript will be reviewed by at least two reviewers.