Cave Fill Research Articles

Identification and Evolution of Different Genetic Types of Deep Karst Caves Controlled by Faults—A Case Study in Huanjiang Sag, Guangxi Province, South China

In recent years, it has become more and more common to drill deep karst caves as a part of deep shale gas resource exploration and engineering construction in South China. However, the amount of research on the genesis and development mechanism of deep karst caves is relatively low. Based on drilling core karst morphology analysis and two-dimensional (2D) seismic and wide-field geophysical exploration methods, it is revealed that the deep karst in the Huanjiang area is mainly composed of net cracks, holes expanding along cracks and dolomite honeycomb pores, and that large karst caves are also developed, which are related to NW-trending faults. The deep karst is developed in the hanging wall of the fault, with a width of 500 m and a height of 1500 m, and a linear distribution along NW faults in the region. Based on Th-U dating, inclusion testing and rare earth elements from cave fillings, it is revealed that the development of deep karst space is related to two deep karst genetic types: The first is the hypogene hydrothermal karst, which developed in the Yanshanian period and is related to regional magmatism. The second is the groundwater deep circulation karst, mainly developed after the Himalayan period, which is related to the deep circulation of meteoric water. The genesis of deep karst space is the result of multi-stage karst superposition and is mainly controlled by faults. It is difficult to determine the specific time points of these two types of deep karst transformation, but according to regional tectonic evolution, we speculate that the Yunnan-Guizhou Plateau has been uplifted since the Himalayan period (>3.54 Ma), and the Carboniferous carbonate rocks and early faults in the Huanjiang area have been exposed, leading to the change and evolution of deep karst. Through comprehensive analysis, a fault-controlled hypogene hydrothermal karst pattern and a meteoric water deep karst pattern are established. The genetic pattern of deep karst provides theoretical support for predicting this kind of karst in southern China and for avoiding drilling deep karst caves as a part of resource exploitation.

Hierarchical Modeling of Carbonate Fault-Controlled Paleokarst Systems: A Case Study of the Ordovician Reservoir in the Tahe Oilfield, Tarim Basin

As a special type of fracture-cavity carbonate reservoir, fault/fracture-controlled paleokarsts are affected by large strike-slip faults with various storage spaces, irregular geometry, and stochastic spatial distribution, which brings new challenges to their 3D quantitative characterization and geological modeling. Based on multi-scale research data, a hierarchical scheme of a fault-controlled paleokarst is established for the Tahe oilfield, and then a hierarchical modeling method for the paleokarst is proposed based on the principles of hierarchical constraint and genetic control. The results show that the fault-controlled paleokarst hierarchy is divided into four levels according to genesis and scale. These are the strike-slip fault impact zone, the fault-controlled external paleokarst envelope, the fault-controlled internal paleokarst architecture, and the internal karst cave fillings. The strike-slip fault impact zone model is established using deterministic data of the main fault, secondary fault, envelope range, and key geological horizons obtained from seismic interpretation. Based on the seismic FL (Fault Likelihood) attribute, the external envelope model of the fault-controlled paleokarst is established using the deterministic method through automatic attribute segmentation and drilling calibration. With the constraint of the external envelope, the internal architectural elements are classified and modeled. A large-scale karst cave model and mesoscale discrete fracture distribution model are established using the deterministic method based on the seismic texture property and seismic ant property truncation. Taking well data as conditional data and seismic-geological probability cubes as constraint data, the sequential indication simulation and object-based marked point process simulation methods are used to obtain the model of the dissolution pores distribution and the model of the discrete small-scale fractures distribution, respectively. Finally, a typical fault-controlled paleokarst reservoir in the TP area of the Tahe oilfield is taken as an example to test the above modeling method; the 3D integrated model developed in this study can reflect the spatial hierarchy of the fault-controlled paleokarst carbonate reservoir.

Evaluating Claims of Early Human Occupation at Chiquihuite Cave, Mexico

ABSTRACT Archaeologists working in Mexico recently claimed evidence for pre-Last Glacial Maximum human occupation in the Americas, based on lithic items excavated from Chiquihuite Cave, Zacatecas. Although they provide extensive array of ancillary studies of the cave's chronostratigraphic and paleoenvironmental record, the data they present do not support their central argument, that these lithic items are anthropogenic and represent a unique lithic industry produced by early human occupants. They give limited consideration to the most plausible alternative explanation: that the assemblage is a product of natural processes of disintegration, roof fall, and mass movement of the cave fill, and thus the lithic materials are best explained as geofacts. We assess the evidence by considering the alternative hypotheses (1) that the observed phenomena are artifacts or (2) that they result from natural processes. We conclude that hypothesis 2 is more strongly supported and that Chiquihuite Cave does not represent evidence for the earliest Americans.

Speleogenesis and depositional history of paleokarst phreatic caves/cavities; Podgrad, SW Slovenia

The studied paleokarst corresponds to an uplifted peripheral foreland bulge when Upper Cretaceous diagenetically immature eogenetic carbonates were subaerially exposed, karstified and subsequently overlain by upper Paleocene/lower Eocene palustrine limestone.Among the subsurface paleokarstic features, both vadose and phreatic forms occur. The phreatic caves/cavities include features characteristic of the mixing zone speleogenesis at the interface between freshwater (brackish water) lenses and the underlying seawater. They were found in various positions with respect to the paleokarstic surface, the deepest being about 75 m below the surface. Three indistinct horizons of cavities/caves and intermediate vugs were recognized. Subsequently, all cavities were completely filled with detrital sediments and speleothems in the phreatic and vadose zones. In general, the phreatic cavities of the lower two horizons are geopetally filled with mudstone derived from incomplete dissolution of the host rock and overlain by coarse-grained, blocky calcite. Shallower below the paleokarst surface, a large phreatic cave of the third horizon is filled with flowstone overlain by reddish micritic carbonate sediment with intercalated calcite rafts. In the upper part of the cave, sediments derived from the paleokarst surface are gradually becoming more abundant. Vadose channels, which may also intersect the cave sediments, are mainly filled with "pedogenic" material derived from the paleokarst surface. Immediately prior to marine transgression over the paleokarst surface, some cavities were filled with marine-derived microturbidites. In general, the diversity of cave fills and the amount of surface material decrease with distance from the paleokarst surface. Below the paleokarst surface, the δ13C and δ18O values of a host rock and cavity deposits show good correlation with trends significant for meteoric diagenesis. It is shown that deposits associated with phreatic caves can be of great importance for the study of the speleogenetic, geomorphological and hydrogeological evolution of certain paleokarst regions.

Cherts, spiculites, and collapse breccias – Porosity generation in upper Permian reservoir rocks, Gohta discovery, Loppa High, south-western Barents Sea

Spiculitic cherts are uncommon reservoir rocks and their porosity evolution is poorly understood compared to sandstones and carbonates. In the Gohta oil and gas discovery on the Loppa High in the south-western Barents Sea, the reservoir is in brecciated, silicified, and dolomitized Permian spiculites below the Permian/Triassic unconformity. It represents the infill of several collapsed cave systems with spiculite clasts in a micritic matrix, separated by intact cave roofs of shale and spiculite facies. The cave collapse was related to dissolution of less resistant (?limestone and ?spiculitic) beds, due to percolation of freshwater during latest Permian – earliest Triassic emersion. During later transformation of opal-A to opal-CT, associated growth of silica concretions left the margins of spiculite clasts depleted in SiO2 and thus highly porous. Subsequent transformation of opal-CT to quartz resulted in precipitation of texture-preserving quartz and chalcedony cements. The latter show a systematic decrease of δ18O from the first to last precipitated phase, implying crystallization under increasing temperatures during renewed Middle–Late Triassic burial. Later diagenesis includes in situ brecciation and fracturing, dolomitization affecting mainly the micritic matrix of cave-collapse facies, chemical compaction, and calcite cementation. The best reservoir properties are in cave-collapse facies (commonly 10–25% and 0.03–19 mD) where the pore system is dominated by (1) uncemented interspicule pores and central parts of spicule molds within clast margins, and (2) intercrystalline pores between dolomite crystals in the breccia matrix. The primary depositional facies have much lower porosity and permeability (rarely exceeding 10% and 1 mD, respectively). This study shows that porosity in the cave fill most likely formed by local redistribution of silica to form concretions and dissolution of the carbonate matrix to source the growth of dolomite crystals, while prolonged subaerial exposure only played an indirect role by isolating spiculite clasts and preventing their complete silicification during burial.

Heloderma (Helodermatidae; Squamata) from the Apache Local Fauna, Pleistocene, Southwestern Oklahoma

Paleontological occurrences of helodermatid lizards (Helodermatidae) are relatively uncommon and scattered in the North American fossil record. A recently discovered concentration of vertebrate fossils was exposed in a karstic fissure filling in an active rock quarry in southwestern Oklahoma. Underwater screening of the ancient cave fill yielded numerous isolated and fragmentary skeletal elements of a diversity of small, and a few large, vertebrates including unexpected remains of Heloderma sp. as well as extinct large mammals (horse, peccary, Dwarf Pronghorn), indicating Pleistocene age. Radiometric dating of the locality is not possible because of the leaching, but fossils of the Prairie Vole, Microtus ochrogaster, from the locality help to constrain the age of the deposit between 1.21 Ma and 0.01 Ma. The fossils are the first of Heloderma in the Pleistocene of Oklahoma and the southern Great Plains. Based on taphonomic evidence and the relative abundance of rodent teeth, we infer that the fossils accumulated at least partly as the remains of vertebrates fed upon by Ringtails (Bassariscus; Procyonidae) and other small carnivorous mammals. The Pleistocene occurrence of Heloderma in the southern Great Plains of North American has potential implications for the paleobiogeography of the genus and begs further investigation of fossil herpetofaunas in North America.

Origin of fine-grained clastic sediments in caves of the Hoher Göll massif (the Northern Calcareous Alps, Austria)

The Hoher Göll Massif is situated 20 km south of Salzburg and belongs to the Northern Calcareous Alps (Austria). It is a ridge ca. 11 km long and 3 km wide with the highest summit Hoher Göll (2522 m a.s.l.), encircled by deeply incised valleys with bottoms ca. 2,000 m below it. Cave clastic deposits were studied in the Hochschartehöhlensystem, Dämchenhöhle and Hintere caves. The caves belong to the Giant Cave Level, with the exception of part of the Hochschartehöhlensystem, that is Der Sprechender Steine Cave, the highest parts of which belong to the Ruin Cave Level. The sources of the cave sediments have been identified from the composition of the heavy fractions. Preliminary studies of the Hoher Göll caves reveal that the cave fills were derived from the Oligocene to earliest Miocene Augenstein Formation, the deposits of the Palaeo-Inn River and the siliciclastic basal strata of the Northern Calcareous Alps. The clastic material deposited as the Augenstein Formation was transported from southern parts of the Eastern Alps and by the Palaeo-Inn river from their western part. According to heavy minerals, the sources of the clastic material were on the Palaeozoic terrains, the post-Palaeozoic sequence, and the Middle Austroalpine Unit. Later, during or after the mountain uplift, weathered materials from the Augenstein and Palaeo-Inn deposits were eroded and transported from the surface into caves by allogenic streams. Some of the sediments were likely to have been transported later to the Giant Cave Level from the southern part of the Northern Calcareous Alps.

Late Pleistocene Palaeoenvironmental Variations from Marine Isotope Stages 5 and 4: Small Mammals at Artazu VIII Site (Arrasate, Northern Iberian Peninsula)

Sites corresponding to Marine Isotope Stage MIS 5c and MIS 4 like Artazu VIII, with a continental record but no hominin imprints or carnivore activities, are very scarce in the Iberian Peninsula. The Artazu VIII cave fill (Arrasate, northern Spain) was discovered in 2013 and is presented here for the first time, including detailed stratigraphic and sedimentological descriptions of the differentiated 12 levels, as well as an ordered chronology of most levels, covering at least 36.000 years. In addition, the small mammal assemblage yielded a total of 8,129 identifiable skeletal remains corresponding to 14 taxa. The conditions inferred from the ecological preferences of the small mammal associations have been correlated with four different stages and substages from MIS 5c to MIS 4 in which the woodland mass expanded and retreated, depending on the relative temperature and humidity in each period. Finally, considering the species variability and estimated palaeoenvironment, a comparison with the NGRIP δ18O curve and other sites with the same chronology has been performed, showing that Artazu VIII is one of the few deposits attributable to the Marine Isotopic Stages previously mentioned and the only one that correlates to the Greenland Interstadial 18 from the Iberian Peninsula.

Post-Neolithic occupation in Tunel Wielki Cave (southern Poland)

Post-Neolithic cave occupation in Poland remains insufficiently recognised. The purpose of this paper is to present the results of the analysis of pottery and metal objects discovered in Tunel Wielki Cave (Ojców area, SE Poland). The artefacts were collected during three fieldwork campaigns in 1967–68 and 2018. The results show that the cave was occupied at least several times. The most ephemeral settlement traces can be dated to the Early Bronze Age and these may be related to the Trzciniec culture. The site was more intensively used in the Late Bronze Age and Early Iron Age by communities representing the Lusatian culture. Roman Period artefacts are very scarce. Traces of most intensive use of the cave come from the Middle Ages. One can determine artefacts conditionally dated from the 11th to the 12th century, as well as younger objects, dated to the 13th − early 14th c. Single pieces of pottery can be attributed to the Modern period. The obtained results point to multiple short-term visits. The cave fill does not bear traces of permanent occupation during the Post-Neolithic period.

Link of laminated crusts associated with pisolites to sea-level change: A case study from the Ladinian (Middle Triassic) Longtou Formation, Guizhou, China

The nature (depositional or diagenetic) of laminated crusts associated with pisolites is still in debate, which hampers the interpretation of sea-level change on carbonate platforms. The Ladinian Yangtze platform margin, formed by the Longtou Formation, contains abundant laminated crusts associated with pisolites, providing an opportunity to decode their formation in response to sea-level variations. There, individual laminae are formed of isopachous radiaxial fibrous calcite (RFC) crystals. The RFC displays strong undulose extinction and orange-red or dull red cathodoluminescence. The pisolites (vadoids) coexisting with the laminated crusts are characterized with inverse graded bedding, stalactitic cements, and red luminescence or non-luminescence. The laminated crusts and associated pisolites have δ18O values ranging from −10.56‰ to −3.83‰ and from −7.12‰ to −6.33‰, respectively, which are more negative than that of the Ladinian normal seawater. They also share similar rare earth element and yttrium (REE + Y) distribution patterns, with enriched heavy rare earth element (HREE), enriched Y element, true negative Ce anomalies, and Y/Ho ratios between 34 and 51. Detailed petrographic and geochemical analyses indicate that the laminated crusts and associated vadoids formed in caves in response to alternating meteoric water and seawater, with the fluctuating water table resulting in their mixed deposition. The preservation of laminated crusts and vadoids in the Longtou Formation implies that they formed during a period of overall sea-level transgression, which was punctuated by sea-level regression and allowed formation of cave fillings. Our results suggest that laminated crusts present in ancient carbonate successions may indicate the positions of subaerial exposure related to sea-level regressions.

Geochemistry of the fracture-cave calcite of the Ordovician Yingshan Formation and its paleokarst environment in the Tazhong area, Tarim Basin, China

The fracture-cave reservoir of the Yingshan Formation is an important oil and gas producing zone in the Tarim Basin. Karstification occurs at the top surface of the carbonate rocks of the Yingshan Formation on the northern slope of the Tazhong area due to a short exposure, so abundant fracture-cave spaces are formed. On the basis of the data of nearly 49 samples obtained from 21 wells, the carbon and oxygen isotopes of the fracture-cave calcite were analyzed. The carbon and oxygen stable isotopic characteristics recorded during paleokarstification were discussed to provide geochemical evidence for predicting the distribution of the fracture-cave reservoirs, as well as to understand the genetic mechanism of karst fracture-caves and the fluid properties and paleo-hydrological conditions of paleokarstification. The fracture-cave calcite can be divided into three types based on its carbon and oxygen isotope values, which indicate three types of paleokarst environments with different fluid properties. Type I calcite has similar carbon and oxygen isotope values to the bedrock of the Yingshan Formation, with δ13C values of − 2.0 to 1.1‰ and δ18O values of − 5.76 to − 8.16‰. These values indicate that the calcite was precipitated in the eogenetic karst environment of the Yingshan Formation. Type II calcite has a δ13C value of − 2.13 to 1.0‰ and a δ18O value of − 12.41 to − 8.0‰. It has a similar δ13C value, but a significantly negative oxygen isotope value compared with values of the bedrock of the Yingshan Formation, indicating a buried karst environment. Type III calcite has an extremely negative δ18O value (δ18O value < − 14.50‰), indicating hypothermal karst genesis. Its formation is related to magma or deep hydrothermal fluids. No calcite with atmospheric freshwater genesis and significantly negative δ13C and δ18O values was found in the samples, indicating that the formation of fracture-caves is weakly affected by atmospheric freshwater. The main reservoir space of the Yingshan Formation is karst caves. The calcite in the karst cave fillings belongs to type I, indicating an eogenetic karstification environment. Therefore, the formation of the fracture-cave reservoirs of the Yingshan Formation in the Tazhong area is related to eogenetic karstification, which occurred during exposure and mainly contributed to the formation of the reservoir spaces.

Multiscale geological-geophysical characterization of the epigenic origin and deeply buried paleokarst system in Tahe Oilfield, Tarim Basin

Abstract The irregular structures of paleokarst systems are among the major factors resulting in carbonate reservoir heterogeneity, which restricts the further exploration of paleokarst reservoirs. Using multiscale geological-geophysical (G&G) data, including thin-section, core-sample and well-log data, the caves, cave fillings and fractures in individual wells in the northern Tahe Oilfield were characterized. Guided by seismic datasets, the interwell paleokarst structures were interpreted in profile and plane view. The paleokarst system in the study area was divided into four vertical zones, and the relative genetic structures were classified in the upper three zones. The epikarst zone includes paleo-canyons, karst towers, dolines, paleo-soils, and fractures, and the water flows horizontally. The vadose zone includes vadose caves and fractures, and the water flows vertically. The epiphreatic zone includes chambers, main channels, branch channels and fractures, and the water flows primarily horizontally along the water table. For each genetic type, the total hydrocarbon production and monthly production were analyzed. Furthermore, a genetic classification model was built for the paleokarst reservoirs of the study area, which increased our understanding of the structure of the paleokarst system. The results of the structure classification and production analysis can effectively guide hydrocarbon exploration, and this approach can be applied to similar paleokarst reservoirs.

Model identification and control of development of deeply buried paleokarst reservoir in the central Tarim Basin, northwest China

The paleokarst reservoirs of the Ordovician Yingshan formation, rich in oil and gas, are deeply buried in the central Tarim Basin, northwest China. Dozens of imaging well-logs in this region reveal five typical paleokarst features, including solution vugs, solution-enlarged fractures, filled caves, unfilled caves and collapsed caves, as well as two typical paleokarst structures located in different paleotopographic sites, including paleokarst vadose and phreatic zones. For seismic data, the large wave impedance contrast between the paleocave system and the surrounding rocks leads to a strong seismic reflection, which is highlighted as a bead-like 'bright spot' in a seismic section. By quantitatively estimating the seismic resolution limits of deep seismic reflections, a single paleocave cannot be identified from a seismic profile, and the bead-like reflection represents an entire paleocave complex. The spectral decomposition technique was employed to depict the planar shape and semi-quantitatively measure the size of the paleocave complexes. The results indicate that the sizes of the paleokarst caves are all small, and most of the karst caves are nearly completely filled by clay and calcite. The small cave size and the effective support of cave fills for the overlying strata mean that some individual paleocaves in a paleocave complex are preserved at a burial depth of more than 6000 m. Paleotopography and faults strongly impact the distribution of paleokarst reservoirs. Well-developed paleokarst reservoirs are generally located in paleotopographic highlands and on slopes, and for a specific paleotopographic site, the distribution of paleokarst reservoirs is obviously controlled by NW-SE trending faults. The most favorable area for paleokarst development is the Tazhong No. 10 fault zone, a faulted anticline bounded by two NW-SE trending back thrusts.

Basalt Intrusions in Palaeokarst Caves in the Central Lessini Mountains (Venetian Prealps, Italy)

The Lessini Mountains carbonate plateau (Venetian Prealps, Italy) is one of the most important karst areas in Italy. Along with alpine-type caves and well-developed karst landscapes, palaeokarst features are also common. In most cases, palaeokarst is represented by caves and fissures filled by limonitic-haematitic palaeosols (ochres) in which fossiliferous arenite layers are sometimes embedded. These features developed and fossilised during a late Eocene-middle Miocene phase of emersion. Between the Palaeocene and the Oligocene, over a time span partially overlapping the development of palaeokarst, basaltic volcanism took place in the Lessini Mountains. Along with ochre fills, cave passages that were intruded by basalt provide further evidence that a well developed karst network existed in the Lessini Mountains area in the middle-late Palaeogene. Moreover, basalt intrusions provide the only available data for the dating of palaeokarst in the central Lessini Mountains, where fossiliferous layers in ochre beds have not been found. We have started a new survey on palaeokarst in the Lessini plateau, with the aim of identifying ancient features on the basis of unusual fills (namely, ochre and basalt) and morphologies. New instances of basalt intrusions in three caves, Spigola di Canova, Covoli di Velo, and Covolo della Croce, have been recognised; evidence of pre-existing karst features filled by basalt in a previously studied cave (Grotta A Veja) has been identified, and an unusual basalt outcrop that might relate to palaeokarst has also been observed. This paper aims to document the new findings and to discuss previous ones. At the same time, we would like to point out some cautionary observations to prevent a “basalt = palaeokarst” misunderstanding. Key words: palaeokarst, basalt intrusion, cave fills, Lessini Mountains.

Structure and Filling Characteristics of Paleokarst Reservoirs in the Northern Tarim Basin, Revealed by Outcrop, Core and Borehole Images

AbstractThe Ordovician paleokarst reservoirs in the Tahe oilfield, with burial depths of over 5300 m, experienced multiple phases of geologic processes and exhibit strong heterogeneity. Core testing can be used to analyse the characteristics of typical points at the centimetre scale, and seismic datasets can reveal the macroscopic outlines of reservoirs at the &gt;10-m scale. However, neither method can identify caves, cave fills and fractures at the meter scale. Guided by outcrop investigations and calibrations based on core sample observations, this paper describes the interpretation of high longitudinal resolution borehole images, the identification of the characteristics of caves, cave fills (sedimentary, breccia and chemical fills) and fractures in single wells, and the identification of structures and fill characteristics at the meter scale in the strongly heterogeneous paleokarst reservoirs. The paleogeomorphology, a major controlling factor in the distribution of paleokarst reservoirs, was also analysed. The results show that one well can penetrate multiple cave layers of various sizes and that the caves are filled with multiple types of fill. The paleogeomorphology can be divided into highlands, slopes and depressions, which controlled the structure and fill characteristics of the paleokarst reservoirs. The results of this study can provide fundamental meter-scale datasets for interpreting detailed geologic features of deeply buried paleocaves, can be used to connect core- and seismic-scale interpretations, and can provide support for the recognition and development of these strongly heterogeneous reservoirs.

Environmental and geochemical significance of carbon and oxygen isotopes of Ordovician carbonate paleokarst in Lunnan, Tarim Basin

In the Lunnan area of the Tarim Basin, the fracture cave system of the Ordovician carbonate paleokarst, with strongly heterogeneous well-developed corrosion pores, caves, fissures, and a large underground water system, is buried at depths of 5068.51–5709.74 m. There has been little research on the carbon and oxygen isotopic characteristics of the cave fills of the middle–lower Ordovician karst within this area, and little is known about the regional karst developmental stages and their filling environments. In this work, systematic geochemical studies were conducted on the carbon and oxygen isotopes of 47 karst fill samples, based on which the developmental stages of the paleokarst and their characteristic filling environments were determined. Four different karstification stages were identified together with their filling environments. The results revealed δ13C (PDB) values within the range of 6.06 to −8.69 ‰ with an average of −1.40 ‰ and δ18O values within the range of −5.78 to −17.28 ‰ with an average of −10.74 ‰. The calculated deposition temperatures of the karst fracture caves were between 2.24 and 55.84 °C with an average of 22.06 °C. The Z values of the characteristic medium salinity were between 104.33 and 133.47 with an average of 119.06. Both the δ13C and the δ18O values exhibited broad ranges, resulting in a large span of calculated temperature differences that drift to opposite ends, revealing the complex and multiphase nature of the carbonate karstification process and the respective filling environments within this area.

The Caledonian paleokarstification of Longwangmiao Formation, Lower Cambrian in the central Sichuan basin, China

Longwangmiao Formation in Lower Cambrian is one of the key petroleum systems in Sichuan basin. The reservoir is well developed in the Longwangmiao Formation which was deposited in the restricted carbonate platform. It is indicated that the karstification occurred in the reservoir of Longwangmiao Formation during the Caledonian tectonic movement on the basis of seismology, petrology, sedimentology and geochemistry. Distinguishable markers of the paleo-karstification include: the lost strata and unconformable contact occurring between Middle-Upper Cambrian carbonates and Lower Permian Liangshan Formation; the occurrence of collapse breccias and fillings in caves and karrens; the evident difference between cave fill dolostones and matrix dolomite in the Sr/Ba ratio; and the log response of cavernous formations. The karstification lasted for a long time. According to the residual thickness between the top of Longwangmiao Formation and the bottom of the Permian, paleo-geomorphology during the Caledonian karstification had been recovered. In that time, Longwangmiao Formation was not directly exposed to the surface in central Sichuan basin; lots of meteoric fresh water flowed through faults and cracks from Gaotai Formation and a series of vertical dissolved caverns and karrens were formed. Meanwhile, due to the denudation window of Leshan-Longnvsi paleo-uplift lying in the west of the study area, meteoric fresh water flowed from the denudation window and the Longwangmiao Formation became a karstic confined aquifer. Under the pressure, diagenetic fluid migrated along the formation. Consequently, elongated dissolved pores and vugs formed and bedding karst reservoir developed in Longwangmiao Formation. The intensity of the karstification weakened with the distance from the paleo-uplift increasing, which indicates that the karstification was deeply influenced by the paleo-uplift. Finally, the supergene karstification model of Longwangmiao Formation has been established on the basis of the synthesis of the above-mentioned research results.

Hypogene Sulfuric Acid Speleogenesis and rare sulfate minerals in Baume Galinière Cave (Alpes-de-Haute-Provence, France). Record of uplift, correlative cover retreat and valley dissection

The oxidation of hydrocarbons and sulfide sources (H2S, pyrite) produces sulfuric acid that strongly reacts with bedrock, causing limestone dissolution and complex interactions with other minerals from the bedrock or from cave fillings, mainly clays. This type of cave development, known as Sulfuric Acid Speleogenesis (SAS), is a subcategory of hypogene speleogenesis, where aggressive water rises from depth. It also produces uncommon minerals, mainly sulfates, the typical byproducts of SAS. Baume Galinière is located in Southern France, in the Vaucluse spring watershed. This small maze cave displays characteristic SAS features such as corrosion notches, calcite geodes, iron crusts, and various sulfate minerals. Sulfur isotopes of SAS byproducts (jarosite and gypsum) clearly show they derive from pyrite oxidation. Using XRD and micro-Raman spectroscopy, thirteen minerals were identified, including elemental sulfur, calcite, quartz, pyrite, goethite, gypsum, and fibroferrite, plus all of the six members of the jarosite subgroup (jarosite, argentojarosite, ammoniojarosite, hydroniumjarosite, natrojarosite, plumbojarosite). The Baume Galinière deposits are the first documented cave occurrence of argentojarosite and the second known occurrence of plumbojarosite, hydronium jarosite, ammoniojarosite, and fibroferrite. In the Vaucluse watershed, there were numerous upwellings of deep water along major faults, located at the contact of the karstic aquifer and the overlying impervious covers. The mixing of deep and meteoric waters at shallow depths caused pyrite depositions in numerous caves, including Baume Galinière. Sulfuric Acid Speleogenesis occurred later after base-level drop, when the cave was under shallow phreatic conditions then in the vadose zone, with oxidation of pyrites generating sulfuric acid. Attenuated oxidation is still occurring through condensation of moisture from incoming air. Baume Galinière Cave records the position of the semi-impervious paleo-cover and documents its retreat in relationship to valley incision caused by uplift and tilting of the Vaucluse block during the Neogene.

Sedimentation, re-sedimentation and chronologies in archaeologically-important caves: problems and prospects

Excavations in the photic zones of caves have provided cornerstone archaeological sequences in many parts of the world. Before the appearance of modern dating techniques, cave deposits provided clear evidence for the antiquity, relative ages and co-occurrence of ancient human remains, material culture and fauna. Earlier generations of archaeologists had generally rather limited understanding of taphonomic and depositional processes, but the twentieth century saw considerable improvement in excavation and analytical techniques. The advent of modern dating and chronological methodologies offers very powerful tools for the analysis of cave fill deposits and this has resulted in the recognition of chronological incoherence in parts of some sites, with consequent re-evaluation of previous archaeological disputes. Obtaining multiple dates per context provides a means to assess the integrity and coherence of the archaeological and environmental records from cave fills. In the case of the Haua Fteah (Libya), this technique allowed the recognition of chronological coherence in low-energy depositional environments and limited recycling in high-energy contexts. We provide a conceptual model of the relationship between recycling, sedimentation rate and process energy. High-resolution investigation enables recognition of the complexity of the formation of cave sequences, thus an increasingly sophisticated understanding of human behaviour and environmental relationships in the past, and potentially gives a new life to old data.

Early–Middle Holocene environmental changes and pre-Neolithic human occupations as recorded in the cavities of Jebel Qara (Dhofar, southern Sultanate of Oman)

Numerous palaeoenvironmental and archaeological studies from southern Arabia (Yemen and Oman) have revealed strong relations between phases of human settlements and climate change linked to the Indian monsoon system. Analyses on speleothems, cave fills, lacustrine deposits and palaeo-mangroves have shown that during the Early to Mid-Holocene, a humid Optimum culminated around 9000–8000 cal BP. New results on inland speleothems and cave sediments from the Jebel Qara (southern Oman) are crucial in our depiction of Early and Mid-Holocene climatic evolution and cultural dynamics of the region. These aspects are discussed here, based on new archaeological surveys, excavations, geoarchaeological and micromorphological studies, aiming to better understand connections with Terminal Pleistocene and Early Holocene autochthonous cultures of southern Arabia. Our results suggest that the final Pleistocene was marked by strong aridity, which promoted a widespread thermoclastism within rock shelter and deposition of aeolian sand; in contrast, the transition towards the Holocene is marked (since c. 12,000 cal BP) by a progressive increasing in environmental humidity, which permitted the formation of thick strata of peridesert loess. After this phase, the environmental humidity of the Jebel increased and permitted the existence of a large community of land snails; the latter were exploited by Early Holocene hunter–gatherers who lived in the rock shelters between c. 10,500–9500 cal BP and left consistent accumulations of land shells (escargotières). The maximum of Holocene humidity was reached between 9000 and 8000 cal BP; regional aquifer were recharged and the deposition of calcareous tufa at the entrance of caves started, lasting up to c. 4500 cal BP. C and O stable isotopes from calcareous tufa highlights, in accordance with several regional records, the progressive decline of the intensity of the Indian Ocean monsoon and the transition towards arid conditions. In this phase, the area was abandoned and archaeological communities possibly relocated along the coast of central and southern Oman, where they exploited the mangrove environment.