Clastic deposits in Kalacka Cave in the Tatra Mts. Show soft-sediment deformation structures (SSDS) rare for a cave environments. The poorly sorted allochthonous sediments were deposited within a ...cave sump under a fluvial regime, likely due to glacially initiated back-flooding during the Last Glacial. The structures include small-scale faults (normal and reverse), folds (upright symmetric anticlines, low-amplitude open folds, W-vergent folds and fault-propagation folds), and water-escape structures. A laboratory experiment is used to assess the possibile liquefaction of a thin soft-sediment filling in a limestone tube, including calculation of the site effects of resonance frequency and amplification coefficient and the site vulnerability index Kg. The calculations indicate that seismic waves can be amplified up to 10 times and the expected resonance frequency is ~17.05 Hz.
We argue that the observed SSDS formed in two stages. First, brittle and ductile deformation structures developed due to gravity-induced slumping. Next, liquefaction produced water-escape structures. The studied SSDS were likely seismically triggered. Favorable conditions occurred during the withdrawal of the last glacier (MIS 2) when the sediments were oversaturated and the Tatra Mts. experienced a strong earthquake (M7.0). Alternatively, high-frequency microearthquakes could have been triggered by slope failure cutting into Kalacka Cave.
•The clastic sediments of Kalacka Cave a rare record of SSDS.•A first estimation of the site effects and the vulnerability index of cave sediments.•The SSDS in Kalacka Cave are likely co-seismic.•The optimal time for the SSDS development in the cave was the end of the Last Glaciation.
An interpretation of the archaeological record, in particular that of a prehistoric cave site, is complicated by the diversity of depositional and post-depositional processes that affect the material ...deposited. Here we propose to use the authigenic minerals that form in situ within the cave sediments to reconstruct the ancient chemical environments in the sediments. This can be done by experimentally determining the conditions under which each of the authigenic minerals are stable. Although this information is not available to date for minerals formed in a prehistoric cave, we present calculated stability field data for the relevant minerals. The results clearly demonstrate the feasibility of this approach. This information, particularly if based on measurements of real authigenic cave minerals, will facilitate an assessment of the completeness of the cave archaeological record. This is particularly important for determining whether or not the distributions of archaeologically important materials, such as bones, teeth, plant phytoliths, charcoal and ash, reflect their original burial distributions or were altered as a result of secondary diagenetic processes.
The post-depositional alteration of cave sediments is of critical importance for the recognition, identification and investigation of geoarchaeological and palaeoenvironmental evidence. There have ...been relatively few studies of tropical cave sediments using micromorphology and this work represents one of the most detailed with 26 samples taken from deposits in the West Mouth of the Great Cave of Niah that cover the last >∼55,000 BP, and contain the earliest known evidence for the remains of modern humans in Southeast Asia. Cave sediments situated in the humid tropics are subject to relatively high temperatures and moisture conditions that promote high rates of chemical alteration and geomorphic change. This paper outlines those post-depositional features that occurred in situ in the West Mouth and include: translocation and concentration; bioturbation; excrement; bone alteration; plant alteration; clast alteration and guano decomposition. It examines their implications for recognising past human activities (e.g. fire-altered materials), the preservation of archaeological remains, the nature of palaeoenvironments and of localised physical and bio-geochemical processes.
•Micromorphology reveals in detail the breakdown of humid tropical cave sediments.•Wide range of post-depositional alteration features in humid tropical cave sediments.•Alteration features change in their relative abundance over the past ∼55,000 years.
We synthesize information on results and age of cave sediments from Slovenia. The studied sites were mostly from the Classical Karst which is situated in the NW part of Dinarides and some from the ...Slovenian Southern Alps. Protected in caves, sediments are generally well preserved and reveal an exceptionally good, multi-proxy record of surface environmental conditions at the time of their deposition. Here we describe results of the systematic acquisition of palaeomagnetic data within individual segments of studied sediment sections with special focus on relict and unroofed caves. In intervals with polarity change, the frequency of sampling was so high that almost continuous records of rockmagnetic and palaeomagnetic parameters were obtained. The construction of high-resolution magnetostratigraphic profile supported magnetostratigraphy correlations among profiles. Palaeomagnetic and magnetostratigraphy results were calibrated by relative, numerical, calibrated and correlated dating methods, where possible. Age sequences were compiled from spatially and temporally highly discontinuous sediment records covering different ages within the Cenozoic era. The robust chronology was constructed. Calibrated data contributed to the interpretation of speleogenesis, deposition mechanism in caves, and indirectly to the time of karst evolution and the succession of tectonic phases and climate changes. The research indicated that most of sediments in relict and unroofed caves are up to 5 Ma old which contrasts to the traditional concept of Pleistocene age of cave sediments and that caves themselves are not much older. Cave sediments have proven to be an important source of information on depositional style in caves which indirectly reflected the evolution of the surrounding landscape especially the evolution of catchment areas – i.e. climatic changes with flood events or/and changes of the tectonic regimes during Cenozoic.
During archeological excavations in the Lower Cerovačka Cave (Mt. Velebit, Croatia), the test trench penetrated to a depth of 1.8 m. An undisturbed sequence of sediments was exposed. Considering that ...caves represent highly efficient sediment traps it was possible to recognize changes in the depositional mechanisms during the Pleistocene–Holocene period. Using the multiproxy approach, the mineralogical, petrographic, and biostratigraphic characterization of the cave sediments was performed. Facies analysis revealed several stages in the development of the clastic filling of cave channels. Allochthonous origin of the sediment was assumed. Sedimentation took place under various conditions from pronounced cold and dry climate during Pleistocene stages in the base of the profile, to humid periods with anthropogenic influence during the Holocene at the very top of the profile. Although traditionally these sediments were believed to be of a Pleistocene age, here for the first time a stratigraphic calibration of the profile has been performed based on luminescence dating of detrital cave sediments and radiometric dating of speleothems.
By observing the fluctuations in direction and intensity of the Earth's magnetic field through time, we increase our understanding of the fluid motions of the Earth's outer core that sustain the ...geomagnetic field, the geodynamo. Recent archaeomagnetic studies in the Near East have found extremely rapid increases – ‘spikes’ – in geomagnetic field intensity at ca. 3000 yr cal BP. These observations have proved problematic for our current understanding of core-flow. However, until now, these geomagnetic spikes had not been observed outside of the Near East, where they have been preserved in metallurgical slag and fired, mud brick walls.
We present a new, fully oriented, geomagnetic secular variation and relative palaeointensity (RPI) record for the last 17,000 yr from Hall's Cave, Texas, whose complete, >3.8 m thick sedimentary sequence spans from the present to 16,850±110 RC yr BP (Modern to 20,600 cal BP). Within the stable, cool climate of the cave, pedogenic and bioturbation processes are negligible to non-existent, thereby limiting post-depositional physical and geochemical alteration of the magnetic record. The sub-aerial and subterranean setting of the sedimentary sequence in Hall's Cave enabled us to collect oriented palaeomagnetic cubes from a previously excavated stratigraphic section.
The palaeomagnetic samples yielded high-quality vectors. An age model for the sequence, determined using 15 AMS 14C-dates on individual bones from microvertebrates, was combined with the palaeomagnetic data to construct a secular variation record. The record is in broad agreement with predictions by Holocene field models for the site's location. However, starting ca. 3000 yr ago, the RPI data indicate an almost four-fold increase in geomagnetic field intensity lasting several hundred years. This record presents well-dated evidence, obtained using conventional techniques, for the existence of a geomagnetic intensity spike in North America that is contemporaneous with the shorter duration, decadal-scale spikes reported from the Near East.
•Fully oriented secular variation record for the last 17 ka from Hall's Cave, Texas.•Evidence for dramatic geomagnetic intensity spike ca. 3000 yr ago.•Possibility of global intensity spike or geodynamic teleconnection with Near East.
The mineral components of the sediments that accumulate in an archaeological site constitute a potentially rich source of information on the diagenesis, and in turn the archaeology of the site. This ...detailed three-dimensional study of the mineral assemblages in mainly the Mousterian sediments of Hayonim Cave incorporates more than 2100 infrared analyses performed on-site during the excavation, as well as diverse analyses in the laboratory. Three major mineral assemblages are identified: the calcite-dahllite (CD) assemblage, the assemblage comprising mainly montgomeryite, leucophosphite and siliceous aggregates (LMVS), and a highly altered sediment in which the clays have broken down and silica was released. The boundaries between these assemblages were mapped in detail. The overall picture is one of extreme heterogeneity with sharp variations occurring over distances of a few centimetres. The relation between the CD and LMVS assemblages shows that it is a product of post-depositional diagenesis, whereas the altered clay assemblage formed beneath an erosional unconformity. The CD and LMVS assemblages were derived primarily from an accumulation several metres thick of ash deposits produced by humans. Ash is thus shown to be a major component of the sediments of this cave. The distribution of the CD assemblage reflects to a large extent the locations of two active springs/seepages in the cave. The distribution of the CD assemblage also faithfully maps the distribution of bones in the cave, showing that their distribution is a function of preservational conditions and not human activities (Stineret al ., 2001). The conditions that produced the erosional unconformity, also resulted in severe alteration of the clays and other mineral components of these sediments. The erosion process and the fact that the thickness of this altered zone decreases towards the centre of the cave, indicates that the diagenetic driving force was probably climatic. The three-dimensional distributions of the mineral assemblages have a direct bearing on the dating of the cave by thermoluminescence and electron spin resonance.
The sedimentological record in the Račiška pečina cave sediment sequence is one of the best-preserved cave records of palaeoenvironmental changes for the last 3.4 Ma. However, as it is typical for ...cave terrestrial records, it contains many hiatuses in sedimentation. The section study helped to change the state of knowledge and understanding of the long-lasting deposition characteristics in the caves and provided enormous data on environmental changes over time. In the sequence are by magnetostratigraphy well recorded Pliocene/Pleistocene transition at 2.59 Ma, the Matuyama/Brunhes boundary at 0.773 Ma, and the presence of Olduvai subchron between 1.78 and 1.925 Ma. Records of small mammals from the lower part of the section (a molar of Apodemus cf. atavus and dental fragments of Borsodia sp., and Pliomys sp.) suggest MN17 age, Clethrionomys cf. glareolus from the upper part suggests the Late Early or Middle Pleistocene age. Also worth mentioning are records of snail shells Aegopinella sp. and a troglobiont snail Zospeum sp. In the upper part of the section Ursus ex gr. spelaeus was confirmed in the yellow clay layer older than ~72 ka, and soot material at the top of the section was radiocarbon dated on ~11 ka, ~9 ka, and ~3 ka. A detailed chronology of the Račiška pečina section based on magnetostratigraphy and isotopic oxygen stratigraphy was created and correlated with palaeontological, U-series, and radiocarbon results. Before the hiatus 2.6-2.5 Ma ago, the oxygen record was mainly shaped by regional Mediterranean Sea factors. After this boundary, the RP record becomes more similar to the LR04 stack, implying the increased influence of Atlantic Ocean factors.
The mineralogical characterization (bulk and clay fraction) of the endokarstic deposit from Cueva del Ángel site, Lucena (Córdoba, Spain) has been carried out. The samples of the surroundings (within ...an approximate radius of 25 km) and one sample (A-1) from non-archaeological zone in the cave was also studied in order to perform a mineralogical correspondence with the samples of the sedimentary record. Samples of three different profiles and Stratigraphic Units (J/K: Units I, II, III; J/7: Units I, II; 7/8: Unit I) were considered. The mineralogical composition of the samples from the three profiles is similar. Calcite, phyllosilicates and phosphates (mostly apatite group), with minor quartz and dolomite, constitute the mineralogical association of the sediment. The surroundings samples have a similar bulk mineralogical composition than profiles of the sedimentary record, except for the absence of phosphates (associated with the deposit). On the contrary, significant differences were observed in the clay minerals assemblages of the three studied profiles, and also between the Stratigraphic Units. Stratigraphic Unit III of J/K profile and 7/8 profile are dominated by a clay mineral assemblage consisting of smectite, illite and kaolinite. In these samples, the phyllosilicates show a higher degree of ordering, and they are similar to the surroundings samples. The same clay minerals are detected in samples of Stratigraphic Units II of J/7 and J/K profiles (in the last one kaolinite only appears in traces), but the degree of ordering of phyllosilicates is lower. The phyllosilicates present in Stratigraphic Units I from J/K and J/7 profiles exhibited a high degree of degradation, being impossible their identification. This fact could be related to a thermal effect in this zone of the sedimentary record. In fact, X-ray patterns of sample A-1 (located in a non-archaeological zone in the cave) heated to 600 °C and 1000 °C are similar to the XRD of degraded samples from Stratigraphic Units I from J/K and J/7 profiles. SEM study confirms the heating action on phyllosilicates present in some zones of the sedimentary record, where evidences of cracking due to thermal events can be observed on aluminium silicates belonging to Stratigraphic Unit I from J/K and J/7 profiles. Considering the clay mineralogical study, the areas of the sedimentary record affected by fire have been delimited. Therefore, the clay mineralogy study could be used as fireplace tracers in sedimentary records.
•The minerals found are calcite, phyllosilicates and phosphates, with minor quartz and dolomite.•Phyllosilicates are smectite, illite and kaolinite.•In some samples the phyllosilicates appear with high degree of degradation related with a thermal event.•The clay mineralogy study allowed to delimit the area affected by fire in the sedimentary record.•The clay mineral assemblages could be used as fire tracers.
Quaternary climate variability, profoundly impacting the evolution and distribution of plants and animals across the globe, has been reconstructed by many sediment archives. Here, we track past ...changes of temperature, rainfall and plant type by using the n-alkane and glycerol dialkyl glycerol tetraethers (GDGTs), as well as weathering and pedogenesis by mineralogical and geochemical proxies from a 250 cm deep soil sediment profile from the Early Pleistocene deposits in Mohui Cave, southern China. Indices for weathering intensity such as mineral composition (quartz, feldspar and calcite), major element proxies (Ti/Na, Al/Na, Al/Mg, Ti/Mg, CIW, PIA, CPA, CIA), trace element proxies (Ba/Sr and Rb/Sr), and biomarker proxies (OEP, LSR and CPI) show similar secular trends, revealing a three-stage historical accumulation. The high long-chain n-alkane ratios (C31/C29 and (C31+C33)/(C27+C29)) indicate that the vegetation in the region had increases in percentage of woody plants and decreases in herbs during periods of relatively lower temperature and less precipitation, which evidenced from GDGTs, consistent with a weak weathering process influenced by summer monsoon strength. Further, we compared the distribution of these plant types with the taxonomic variation in the vertebrate paleontological fossils excavated from the same profile in Mohui Cave. The distribution of Lufengpithecus appears in only one interval but Gigantopithecus blacki appears throughout the profile, despite an environment that experienced transitional stages from grassland to woodland in relatively cooler and drier conditions. We infer that in face of these climatic changes Lufengpithecus may have preferred to emigrate from the region, while Gigantopithecus blacki may have stayed given that it was limited to staying in its core area.
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