Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 30 for “"Speleothem"”.
-
Speleothem climate capture of the Neanderthal demise
… was to construct a palaeoclimate record using speleothems from Matienzo, northern Iberia, across the period encapsulating the Neanderthal demise. Contemporary cave monitoring of Cueva de las Perlas has demonstrated the potential for speleothems to be used as indicators of past climate and …
-
Speleothem Palaeoclimatology in the Maya Lowlands of Northwestern Yucatán, Mexico
… of climate in the Maya Classic Period from two speleothems in northwestern Yucatán which help address these issues. First, I provide a high resolution δ<sup>18</sup>O record of seasonal climate variability in the Terminal Classic. Using lamina counting and uranium series disequilibrium dating on …
-
Speleothem-Based Hydroclimate Reconstruction of Northeastern Mexico Across the Last Deglaciation
… hydroclimate spanning 21.77 to 11.56 ka using a speleothem from Rioverde, San Luis Potosí, Mexico. We use trace element ratio data to reconstruct local water balance (P - ET) and compare our results to neighboring proxies and climate models to investigate regional coherency and climate forcings. …
-
Paleoclimate reconstructions over the last century from a tropical speleothem on Niue Island, South Pacific
The study examines the question whether speleothems from Niue Island (19°00'S, 169°50'W), a large carbonate platform located at the edge of West Pacific Warm Pool, can serve as archives of hydroclimate controlled by El-Niño/Southern Oscillation (ENSO) and of catastrophic cyclones that frequent the …
-
A central Texas drying event identified at the Younger Dryas-early Holocene transition using coupled speleothem 𝛿¹³C-¹⁴C analysis
… uncertainties. Strong correlations between speleothem 𝛿¹³C and ¹⁴C activities can result from changes in epikarst carbonate dissolution due to variable CO2 ventilation or pore space moisture. A decrease in the proportion of ¹⁴C-free carbon (the dead carbon proportion, DCP) to 0% is …
-
GEOCHEMISTRY AND PETROGRAPHY OF SPELEOTHEMS FROM TURKEY AND IRAN: PALAEOCLIMATE AND DIAGENESIS
Abstract Speleothems contain key archives of palaeoclimatic information, which can be interpreted through multiple geochemical and petrographic proxies, and precisely dated by Uranium Series dating. As U/Th dating is only viable for samples up to approximately 700 kyr of age, U/Pb dating must be …
-
CHARACTERIZATION OF THE NORTHERN HEMISPHERE GLACIAL CYCLE-II AND TERMINATION FROM HIGH RESOLUTION SPELEOTHEM ISOTOPE AND TRACE ELEMENTAL TIME-SERIES DATA, SOUTHWEST UNITED STATES
Absolute dated high-resolution records from two speleothems from the southwestern United States (SW USA) are used to constrain the timing and character of the Penultimate Glacial period (NH Glacial-II) and the following glacial termination (T-II) in the northern hemisphere (NH). Speleothems FS-TR3 …
-
A 20,000 year flowstone record of Gulf of Mexico sourced moisture in Texas
… past periods of warming. As part of this effort, speleothem-based oxygen isotope records have been used to hypothesize the contribution of either Gulf of Mexico (GoM) or Pacific Ocean sourced moisture since the Last Glacial Maximum (LGM) at cave sites across the Southwest. In this study, a new …
-
Late Holocene Paleoenvironmental Reconstruction in Barbados
… using stable and radiogenic isotope ratios in speleothem lamina as proxies. In addition, it introduces the use of novel mineralogical analyses using Raman spectroscopy and large chamber-scanning electron microscopy to supplement the oxygen isotope record. For the past 1,500 years, the …
-
Rates of natural climate change : a study of speleothems
Speleothems (cave calcite) provide many different proxy indicators for palaeoclimatic changes during the Quaternary era. Generally, the occurrence of growing speleothems is a strong proxy for global palaeoclimate, both geographically and through time. A database of speleothem U-Th ages shows some …
-
An examination of trace element concentrations across calcite/aragonite transitions in a Madagascan stalagmite
Calcite and aragonite speleothems have been used for the past few decades to provide paleoclimate information, but in speleothems of mixed mineralogy the signal of mineral changes can complicate understanding of climate signals also present. This mineral signal must therefore be examined and …
-
Organic complexation in karst cave systems: implications for transition metal incorporation into speleothems
… record, secondary cave carbonate deposits, or speleothems, have proven to present particularly valuable archives of numerous environmental processes over a range of temporal and spatial scales. In this context, trace elements included in speleothems are increasingly used to bolster …
-
Physical and geochemical response in cave drip waters to recent drought, central Texas, USA : implications for drought reconstruction using speleothems
… and matrix flow and may provide the preferred speleothem record for reconstructing past droughts in central Texas using trace-elements ratios. Flow-route characteristics of drip sites at other caves that may be expected to show drought response in terms of trace elements include drip rate …
-
Uranium-Lead dating of hominid fossil sites in South Africa
… More recently it has been applied to young speleothem deposits with sufficiently high concentrations of U and low levels of common Pb. In this study U-Pb dating is applied to speleothern deposits in stratigraphic context with the South African hominid fossils. Samples were taken from the …
-
Investigating Mexican paleoclimate with precisely dated speleothems
Speleothems, or sedimentary rocks formed in caves, act as valuable archives of past climate change due to their suitability for U-series dating and high-resolution proxy analysis. These records can provide insights into water availability and controls on hydrology prior to the instrumental record. …
-
Physical and chemical controls on carbonate precipitation in surficial hot springs and subterranean cold springs
… (Qcaicite = 48). Fogelpole carbonates, called speleothem rimmed pools, precipitate from l6°C water with Qcalcite = 2. The much higher Qcalcite values at Yellowstone are probably related to very high concentrations of calcite precipitation inhibitors, SO4 and Mg2+. Plane light and …
-
Investigating Mexican paleoclimate with precisely dated speleothems
Speleothems, or sedimentary rocks formed in caves, act as valuable archives of past climate change due to their suitability for U-series dating and high-resolution proxy analysis. These records can provide insights into water availability and controls on hydrology prior to the instrumental record. …
-
Epikarst control on flow and storage at James Cave, VA: an analog for water resource characterization in Shenandoah Valley karst
… continuous hydrologic data of precipitation, speleothem drips, and an underground stream in James Cave in Pulaski County, VA, were collected to delineate seasonal recharge patterns, estimate effective recharge and catchment areas, characterize the number and permeability of flow paths, and …
-
Structural diagenesis of bed-parallel and bed-normal fractures, Cretaceous Crato Formation carbonate rocks, NE Brazil
… their relationship with exhumation. According to speleothem growth, open and partially occluded joints in the Crato Formation likely provide permeable pathways for water between the superior and middle aquifers of the Araripe Basin. This fluid movement may be enhanced along bedding planes and/or …
Page 1 of 2