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1. Cave life histories of non-anthropogenic sediments help us understand associated archaeological contexts

   https://doi.org/10.1017/qua.2020.72  

   Karkanas, Panagiotis ; Marean, Curtis ; Bar-Matthews, Mira ; Jacobs, Zenobia ; Fisher, Eric ; Braun, Kerstin ( January 2021 , Quaternary Research)

   Abstract Pinnacle Point (PP) near Mossel Bay in the Western Cape Province, South Africa, is known for a series of archaeological caves with important archaeological finds. Extensive excavations and studies in two of them (PP13B and PP5-6) have documented alternating periods of anthropogenic-dominated and geogenic-dominated sedimentation. A variety of caves do not bear evidence of anthropogenic remains. We have studied in detail the remnant deposits of three of them, Staircase Cave, Crevice Cave, and PP29, which have been formed under the same geologic and sedimentary conditions with those with anthropogenic contributions. Their remains are small and patchy but have extensive speleothem formations (as do most caves at PP) that were isotopically analyzed for paleoclimate and paleoenvironmental reconstruction. These caves also offer the opportunity to understand the purely geogenic signature of the PP locality and thus offer a geogenic baseline for the anthropogenic caves. Archaeologists normally focus only on sites with strong anthropogenic signals, but by building cave life histories we “raise the bar” (Goldberg 2008, p. 30) on our contextual knowledge.
2. Cave and rock shelter sediments of southern Africa: a review of the chronostratigraphic and palaeoenvironmental record from Marine Isotope Stage 6 to 1

   https://doi.org/10.25131/sajg.124.0052  

   Stratford, D. ; Braun, K. ; Morrissey, P. ( December 2021 , South African Journal of Geology)

   Abstract Caves and rock shelters contribute important records to local, regional and sub-continental reconstructions of environment and climate change through the southern African Quaternary. Against a backdrop of pronounced climate change, the archaeological record of the Marine Isotope Stage 6 to 1 period in southern Africa documents a remarkable time in the behavioural and technological evolution of anatomically modern humans. Significant evidence of this evolution is represented in diverse components of the sedimentary record in caves and rock shelters in the region. We present a catalogue of published caves and rock shelters in southern Africa that preserve temporally-relevant clastic and chemical palaeoclimatic proxies in order to: (1) facilitate the integration of cave and rock shelter sedimentary data into broader, regional chronostratigraphically-correlated palaeoclimatic sequences; and (2) identify possible areas and proxies that require focused research in the future. To demonstrate the complexity of the Marine Isotope Stage 6 to 1 stratigraphic record and use of palaeoenvironmental proxies, we present three case studies representing interior and coastal contexts: Border Cave, Klasies River Mouth and Pinnacle Point. These examples aptly demonstrate the challenges of these contexts, but also the opportunities for palaeoenvironmental research in southern Africa when conducted through integrated, multidisciplinary approaches. Publishedmore »records of palaeoenvironmental research from cave and rock shelter sequences in southern Africa are heavily biased to the South African coastal areas and the record is temporally and spatially fragmented. However, there are interesting patterns in the chronostratigraphic record and in the distribution of sites within the context of the geology and vegetation ecology of southern Africa that require further exploration. There are also promising techniques in stable isotope analysis that can be applied to abundant sedimentary components found in the region’s caves and rock shelters, and in its museums.« less
3. Underwater cave mapping using stereo vision

   https://doi.org/10.1109/ICRA.2017.7989672  

   Weidner, Nick ; Rahman, Sharmin ; Li, Alberto Quattrini ; Rekleitis, Ioannis ( May 2017 , 2017 IEEE International Conference on Robotics and Automation (ICRA),)

   This paper presents a systematic approach for the 3-D mapping of underwater caves. Exploration of underwater caves is very important for furthering our understanding of hydrogeology, managing efficiently water resources, and advancing our knowledge in marine archaeology. Underwater cave exploration by human divers however, is a tedious, labor intensive, extremely dangerous operation, and requires highly skilled people. As such, it is an excellent fit for robotic technology, which has never before been addressed. In addition to the underwater vision constraints, cave mapping presents extra challenges in the form of lack of natural illumination and harsh contrasts, resulting in failure for most of the state-ofthe-art visual based state estimation packages. A new approach employing a stereo camera and a video-light is presented. Our approach utilizes the intersection of the cone of the video-light with the cave boundaries: walls, floor, and ceiling, resulting in the construction of a wire frame outline of the cave. Successive frames are combined using a state of the art visual odometry algorithm while simultaneously inferring scale through the stereo reconstruction. Results from experiments at a cave, part of the Sistema Camilo, Quintana Roo, Mexico, validate our approach. The cave wall reconstruction presented provides an immersive experience inmore »3-D.« less
4. Drip water δ18O variability in the northeastern Yucatán Peninsula, Mexico: implications for tropical cyclone detection and rainfall reconstruction from speleothems.

   https://doi.org/https://doi.org/10.1016/j.gca.2020.07.008  

   Lases-Hernandez F., Medina-Elizalde M. ( July 2020 , Geochimica et cosmochimica acta)

   This study examines the oxygen isotopic composition (δ18O values) of drip water, rainfall, and groundwater in the Río Secreto Cave system, located in the Yucatán Peninsula, Mexico. The main motivation of this study was to determine the implications of drip water hydrology for the reconstruction of rainfall and for the detection of droughts and tropical cyclones from stalagmite δ18O records. Monitoring of environmental and isotopic conditions was conducted for two years, from June 2017 to April 2019. This study provides the first instrumental evidence of an “amount effect” on interannual timescales in the Yucatán Peninsula. Observed bi-weekly to interannual variability in drip water δ18O values can be explained for individual drips by different integrations of rainfall amount in the time domain. Drip sites within two chambers (stations A and B) integrate 4 to 15 months of rainfall accumulation. Within a third chamber (station LF) one drip site reflects the annual rainfall isotopic cycle with a positive offset and another, the largest rainfall events. During epikarst infiltration, the integration of rainfall amount by drip water reservoirs determines the degree to which they "dilute" a tropical cyclone (TC) isotopic signature. TCs can be detected particularly when: (1) the water volume of themore »reservoir is low, such as during a persistent drought, and; (2) TCs have a sufficiently distinct isotopic signal relative to that of the reservoir prior to the event. TC isotopic signals can "filter through" the system on time scales shorter than the integration time of the reservoir, on the order of a week, in most of the reservoirs examined. In Río Secreto Cave reconstructing precipitation amount and detecting the TC isotopic signatures from stalagmite δ18O are possible, but not in all cases. Our analysis shows that stalagmite δ18O records are more likely to underestimate the magnitude of annual-scale droughts following normal hydroclimate conditions and more likely to record TCs during multiyear droughts than during normal or wet periods. Drip water monitoring results suggest that available stalagmite δ18O records from the Maya lowlands might be underestimating the intensity of paleo-drought events, such as the Terminal Classic droughts associated with the disintegration of the Maya civilization. This study complements the results from Lases-Hernandez et al. (2019) comparing two different sampling protocols and highlights the importance of conducting multiyear monitoring of drip water and rainfall in order to interpret stalagmite δ18O as a paleoclimate proxy.« less
5. Long-term monitoring of drip water and groundwater stable isotopic variability in the Yucata´n Peninsula: Implications for recharge and speleothem rainfall reconstruction

   https://doi.org/doi.org/10.1016/j.gca.2018.11.028  

   Lases-Hernandez, Fernanda Medina-Elizalde ( November 2018 , Geochimica et cosmochimica acta)

   Hydroclimate interpretations of stalagmite δ18O records from tropical regions requires an understanding of the temporal integration of rainfall amount and its isotopic composition by drip waters that form stalagmite deposits. This study presents oxygen (δ18O) and hydrogen (δD) isotopic results from over 1200 groundwater, rainfall and drip water samples, collected at ~weekly time intervals, over three hydrological years at Río Secreto Cave, in the Yucatán Peninsula, Mexico. Cave environmental conditions and the isotopic composition of drip water were monitored in three chambers with different degrees of air ventilation, along with temperature and relative humidity conditions at the surface. We examined 16 drips and observed that annual δD and δ18O variability reflects the isotopic variability of rainfall to varying degrees. The observed annual amplitude of drip water isotopic variability represents between 5% and 95% of that of rainfall, reflecting epikarst water reservoir size and the complexity of flow paths. Drips that closely reflect the isotopic variability of rainfall and best preserve the isotopic signal of individual rainfall events are observed, but they are uncommon. Only two drips out of 16 were found to have potential to record rainfall isotopic shifts associated with tropical cyclones if sampled at weekly resolution. The relationshipmore »between δD and δ18O in drip water suggests that recharge is biased toward the rainy season (June to November), which represents up to 80% of total annual precipitation. We find that over the course of a year most drips reflect the annual δ18O composition of rainfall, in support of quantitative precipitation estimates from stalagmite δ18O records. We find evidence that the effective recharge in this cave system is controlled by precipitation amount and that recharge is not limited to the months when precipitation exceeds evaporation.« less