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Large volumes of carbonate breccia occur in the late syn-rift and early post-rift deposits of the Billefjorden Trough, Central Spitsbergen. Breccias are developed throughout the Moscovian Minkinfjellet Formation and in basal parts of the Kazimovian Wordiekammen Formation. Breccias can be divided into two categories: (i) thick, cross-cutting breccia-bodies up to 200 m thick that are associated with breccia pipes and large V-structures, and (ii) horizontal stratabound breccia beds interbedded with undeformed carbonate and siliciclastic rocks. The thick breccias occur in the central part of the basin, whereas the stratabound breccia beds have a much wider areal extent towards the basin margins. The breccias were formed by gravitational collapse into cavities formed by dissolution of gypsum and anhydrite beds in the Minkinfjellet Formation. Several dissolution fronts have been discovered, demonstrating the genetic relationship between dissolution of gypsum and brecciation. Textures and structures typical of collapse breccias such as inverse grading, a sharp flat base, breccia pipes (collapse dolines) and V-structures (cave roof collapse) are also observed. The breccias are cemented by calcite cements of pre-compaction, shallow burial origin. Primary fluid inclusions in the calcite are dominantly single phase containing fresh water (final melting points are ca 0 degrees C), suggesting that breccia diagenesis occurred in meteoric waters. Cathodoluminescence (CL) zoning of the cements shows a consistent pattern of three cement stages, but the abundance of each stage varies stratigraphically and laterally. delta (super 18) O values of breccia cements are more negative relative to marine limestones and meteoric cements developed in unbrecciated Minkinfjellet limestones. There is a clear relationship between delta (super 18) O values and the abundance of the different cement generations detected by CL. Paragenetically, later cements have lower delta (super 18) O values recording increased temperatures during their precipitation. Carbon isotope values of the cements are primarily rock-buffered although a weak trend towards more negative values with increasing burial depth is observed. The timing of gypsum dissolution and brecciation was most likely related to major intervals of exposure of the carbonate platform during Gzhelian and/or Asselian/Sakmarian times. These intervals of exposure occurred shortly after deposition of the brecciated units and before deep burial of the sediments.
This evolution consists, first in the elaboration of the underground net systems, then in a long polyphased process of filling – emptying the karstic voids, according to the up and down base level changes that occurred almost continuously during the first half of the Tertiary era. The filling sediments are mostly vadose clay deposits, the various ages of which being established from the study of their fossil vertebrate contents (for latest accounts see Pélissié & Sigé 2006). Then, since latest Oligocene times, the Quercy platform was covered with prograding lacustrine sediments of the Aquitaine Basin. Finally, the whole structure was strongly worn down by the so- called Plio-Pleistocene erosional phase: the previously deep underground system became closer to the surface, and was exposed both to erosion and widening, but also Plio-Pleistocene fillings occurred as shown by the fossils they include (Crochet et al. 2006). Among the latter are rare Late Pliocene and Plio-Pleistocene tooth specimens.
For the last decades, a grading system originally installed by the British Cave Research Association (BCRA) helped to assess the precision of cave maps and related data. Although the BCRA grades were spread
over the globe and often used internationally, they were never officially recognized by the International Union of Speleology (UIS). The fact that BCRA revised the grades several times, but that these upgrades
did not necessarily make it to the international users, did not help to avoid confusion. Therefore, several national federations such as the Australian Speleological Federation (ASF) made up their own grading
system, largely based on the BCRA input, but with notable changes. In order to clarify the situation, the UISIC’s working group «Survey and mapping» reviewed the present grading systems in order to get an
official UIS grading system under way. The paper presents these UIS mapping grades. At the 15th International Congress of Speleology in Kerrville (USA), the working group discussed the BCRA and ASF mapping grades, their use, limitations, and possible upgrades for international use within the UIS. The vast majority of the people present agreed that the use of a grading system in speleological mapping was needed in order to inform the map user of the expected accuracy of the map. After a lively discussion, it was seen that the current ASF standards quite closely match the expectations of the group and that they could be upgraded for UIS use. The following tables present the grades, the accuracy of details, additional information, and an explanation which helps to understand the meaning of the tables. The present version was voted by the UIS national delegates in summer 2010 and is therefore officially in use now. The present note uses some brand names for easier understanding of the type of device. In no means,
this is meant to be a support for these devices; it merely uses that name to describe the functioning principle.Technical Note.
The design and construction of engineering structures in karst regions must deal with such challenges as difficulty in excavating and grading the ground over pinnacled rockheads, instability of ground surface, and unpredictable groundwater flow conditions. Detailed subsurface investigation using boring exploration, geophysical techniques, tracer testing, and groundwater monitoring helps optimize foundation designs and minimize uncertainties inherent in their construction. Based on the maturity of karst landscapes, depth and dimension of karst features, and vulnerability of groundwater contamination, methods that have been established to control surface water and groundwater and minimize sinkhole development include relocating structures to a safer site, filling voids/fractures with concrete, soil reinforcement, constructing deep foundations, and remediating sinkholes.
Bacterial diversity in sediments at UNESCO World Heritage listed Naracoorte Caves was surveyed as part of an investigation carried out in a larger study on assessing microbial communities in caves. Cave selection was based on tourist accessibility; Stick Tomato and Alexandra Cave (> 15000 annual visits) and Strawhaven Cave was used as control (no tourist access). Microbial analysis showed that Bacillus was the most commonly detected microbial genus by culture dependent and independent survey of tourist accessible and inaccessible areas of show (tourist accessible) and control caves. Other detected sediment bacterial groups were assigned to the Firmicutes, Actinobacteria and Proteobacteria. The survey also showed differences in bacterial diversity in caves with human access compared to the control cave with the control cave having unique microbial sequences (Acinetobacter, Agromyces, Micrococcus and Streptomyces). The show caves had higher bacterial counts, different 16S rDNA based DGGE cluster patterns and principal component groupings compared to Strawhaven. Different factors such as human access, cave use and configurations could have been responsible for the differences observed in the bacterial community cluster patterns (tourist accessible and inaccessible areas) of these caves. Cave sediments can therefore act as reservoirs of microorganisms. This might have some implications on cave conservation activities especially if these sediments harbor rock art degrading microorganisms in caves with rock art.
In the monsoon tropics of northern Australia, Bullita Cave is the largest (120 km) of a group of extensive, horizontal, joint-controlled, dense network maze caves which are epikarst systems lying at shallow depth beneath a welldeveloped karrenfield. The Judbarra / Gregory Karst and its caves are restricted to the outcrop belt of a thin bed of sub-horizontal, thinly interbedded dolostone and calcitic limestone – the Supplejack Dolostone Member of the Proterozoic Skull Creek Formation. Karst is further restricted to those parts of the Supplejack that have escaped a secondary dolomitisation event. The karrenfield and underlying cave system are intimately related and have developed in step as the Supplejack surface was exposed by slope retreat. Both show a lateral zonation of development grading from youth to old age. Small cave passages originate under the recently exposed surface, and the older passages at the trailing edge become unroofed or destroyed by ceiling breakdown as the, by then deeply-incised, karrenfield breaks up into isolated ruiniform blocks and pinnacles and eventually a low structural pavement. Vertical development of the cave has been generally restricted to the epikarst zone by a 3 m bed of impermeable and incompetent shale beneath the Supplejack which first perched the watertable, forming incipient phreatic passages above it, and later was eroded by vadose flow to form an extensive horizontal system of passages 10-20 m below the karren surface. Some lower cave levels in underlying dolostone occur adjacent to recently incised surface gorges. Speleogenesis is also influenced by the rapid, diffuse, vertical inflow of storm water through the karrenfield, and by ponding of the still-aggressive water within the cave during the wet season – dammed up by "levees" of sediment and rubble that accumulate beneath the degraded trailing edge of the karrenfield. The soil, and much biological activity, is not at the bare karren surface, but down on the cave floors, which aids epikarstic solution at depth rather than on the surface. While earlier hypogenic, or at least confined, speleogenic activity is possible in the region, there is no evidence of this having contributed to the known maze cave systems. The age of the cave system appears to be no older than Pleistocene. Details of the speleogenetic process, its age, the distinctive nature of the cave systems and comparisons with other areas in the world are discussed.
Cave sediments are commonly fine grained and lack macroscopic sedimentary structures. Only a detailed analysis of the micromorphological characteristics permits an accurate determination of the sedimentary dynamics of such cave deposits. Microscopic sorting, grading, clast orientation, lamination, intercalation, deformation structures, and porosity are some of the features used to identify microfacies such as lacustrine, slack water, debris flow, slumping, sheet wash, hyperconcentrated flows, and solifluction. In combination with micromorphological data derived from post-depositional diagenetic trend sand anthropogenic evidence, it is possible to reconstruct the evolution of a cave, and the climatic history and landscape volution of the area.
Small vertically oriented traction carpets are reported from the collapsed sandy fills of 100 m deep Devonian limestone sinkholes underlying the Lower Cretaceous Athabasca oil sands deposit in north-eastern Alberta, Western Canada. Dissolution of 100 m of underlying halite salt beds caused cataclysmic collapse of the sinkhole floors and water saturated sinkhole sand fills to descend very rapidly. Turbulent currents flushed upper sinkhole fills of friable sandstone blocks and disaggregated sand and quartz pebble for tens of metres. Laminar deposits with inverse grading accumulated as many as six to eight curvilinear entrained pebble streaks, 10 to 30 cm long, vertically impinged against the sides of descending collapse blocks. These deposits were initiated as vertically oriented early stage traction carpets that interlocked fine sand grains and inversely graded overlying pebbles entrained below the dilute overlying turbulent flows. Vortexes that flushed these sinkhole fills and induced these depositional processes may have lasted only seconds before the very rapid descents abruptly halted. Some of the fabrics were suspended vertically in-place and preserved from unlocking and obliteration. These small fabrics provide insight into the instability and ephemeral character of the transition from strong gravity-driven grain falls to very early stages of traction carpet formation. These short-lived deposits of very thin sand layers resulted from sufficient incipient frictional freezing that grain interlocking overcame, however briefly, the strong gravity drives of the vertical falls that would have otherwise dispersed grains and obliterated any organized fabric patterns. Tenuous frictionally locked grains were also suspended at the centres of hyperbolic grain fall flows that briefly developed between turbulent flow eddies, some of which were fortuitously preserved. Some of these suspended grain locking zones passed downward onto the relatively more stable surfaces of the rapidly descending block surfaces. The morphogenesis of these early stage traction carpets differ from more fully developed deposits elsewhere because of their short-lived transport, dynamic instability and vertical orientation.
In the monsoon tropics of northern Australia, Bullita Cave is the largest (123 km) of a group of extensive, horizontal, joint-controlled, dense network maze caves which are epikarst systems lying at shallow depth beneath a well-developed karrenfield. The Judbarra / Gregory Karst and its caves are restricted to the outcrop belt of the thin, sub-horizontal, Proterozoic Supplejack Dolostone. Karst is further restricted to those parts of the Supplejack that have escaped a secondary dolomitisation event. The karrenfield and underlying cave system are intimately related and have developed in step as the Supplejack surface was exposed by slope retreat. Both show a lateral zonation of development grading from youth to old age. Small cave passages originate under the recently exposed surface, and the older passages at the trailing edge become unroofed or destroyed as the, by then deeply-incised, karrenfield breaks up into isolated ruiniform blocks and pinnacles. Vertical development of the cave has been generally restricted to the epikarst zone by a 3m bed of impermeable and incompetent shale beneath the Supplejack which first perched the water-table, forming incipient phreatic passages above it, and later was eroded by vadose flow to form an extensive horizontal system of passages 10-20m below the karren surface. Some lower cave levels in underlying dolostone occur adjacent to recently incised surface gorges. Speleogenesis is also influenced by the rapid, diffuse, vertical inflow of storm water through the karrenfield, and by ponding of the still-aggressive water within the cave during the wet season – dammed up by “levees” of sediment that accumulate beneath the degraded trailing edge of the karrenfield. The soil, and much biological activity, is not at the bare karren surface, but down on the cave floors, which aids epikarstic solution at depth rather than on the surface.
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