Holocene-Pleistocene Climate Variability Through Stalagmites

Understanding the changing climate of the past is the key to understanding the changing climate of the present. Historically, various geologic mediums have been used to unearth the mysteries of the ancient past. These include cores of sediment from deep within the oceans, ice cores from glaciers, skeletons of coral reefs, and stalagmites from inside caves. This dissertation aims to shed light on the climate of the past 300,000 years as recorded within the geochemistry of stalagmites from caves in the Bahamas and Iran. With oxygen and carbon stable isotope geochemistry, radiometric dating through Uranium and Thorium, and trace elemental analysis, paleoclimatic environmental conditions are examined in the samples and compared with various other climate archives to better understand the ancient climatic conditions of planet Earth in order to better understand the current and future states of the climate.</p

Dripwater and Calcite Geochemistry Variations in a Monitored Bahamas Cave

A cave‐monitoring study in Hatchet Bay Cave on the island of Eleuthera, Bahamas, has examined the origins of variations in oxygen and carbon isotopic and minor element composition in cave calcites. Every 3 to 8 months, between 2012 and 2016, temperature, humidity, cave air (δ13CCO2), dripwaters (δ18O and δ2H values, and Ca, Sr, and Mg concentrations), and the chemical composition of precipitating calcite (δ18O and δ13C values, and Ca, Sr, and Mg concentrations) were analyzed in two rooms in the cave. Results from the elemental analyses show that throughout the cave prior calcite precipitation was a driver of the elemental chemistry of the precipitated calcites. In addition, cave calcites show that δ13C and δ18O values were positively correlated with Mg/Ca ratios. The Mg/Ca ratios were also positively correlated with lower calcite precipitation rates. Therefore, water/rock interactions may also influence δ13C and δ18O values and Mg/Ca ratios of the calcite. Differences were observed between the two rooms, with the Main Room of the cave exhibiting increased prior calcite precipitation, more ventilation, lower calcite precipitation rates, and δ18O values, which were farther from equilibrium when compared to the more isolated portion of the cave. These results also validated previous interpretations from Pleistocene stalagmites collected from a nearby Bahamian cave suggesting that a positive covariation between Mg/Ca and δ13C values reflects water/rock interactions. Key Points A cave monitoring study was carried out for ~4 years in Hatchet Bay Cave Eleuthera, Bahamas The cave is well ventilated, and prior calcite precipitation and water/rock interactions are drivers of the elemental chemistry Differences in ventilation of the cave demonstrate that certain locations precipitate closer to δ18O equilibrium than other

Climate driven mobility of the early humans in SW Asia; preliminary evidence from Iranian stalagmites

The dynamic interaction between synoptic systems across the Iranian Plateau in West Asia has made this region highly sensitive to climate change. Early human migration routes in the region from Africa to Eurasia are marked by Paleolithic sites and provide a unique opportunity to study the impact of climate variability on early human mobility and settlement. Preliminary results are based on delta 18O and elemental time series from three stalagmites in central-northwest Iran with robust U-Th chronology over the last 450,00 years The data raise the possibility that the Iranian Plateau experienced several episodes of wet conditions during the Paleolithic period. This is in line with findings from a compilation of independent proxy records of lake sediment in northwest Iran and loess deposits in northeast Iran. The fluctuation of Mn abundance and delta 18O values in these stalagmites correlate with the Greenland ice core record (NGRIP) and coincide with periods of high solar intensity in the northern hemisphere. These early results indicate wet conditions may have prevailed over the Iranian Plateau during marine isotope stages MIS5a,b, MIS5c, MIS5e, MIS6b, MIS6d-e and most likely also during stages MIS3-4 and MIS7a. Early human occupation of the Southern Caucasus, Zagros, and the Near East regions coincides with the upper Pleistocene wet periods. The co-variability between the proxy data from these speleothems and solar insolation at 30 degrees N suggests that early human settlements/occupations may have been more prevalent along coastal regions of the Near East during dry climate episodes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode

Speleothem records of glacial/interglacial climate from Iran forewarn of future Water Availability in the interior of the Middle East

This study presents the first absolute-dated record of climate variability constructed by oxygen isotopes (δ18Oc) from stalagmites in the interior of West Asia (Middle East) that encompass the Last Interglacial and early glacial periods (73,000–127,000 Before Present, BP) and early Holocene (6500–7500 BP). Variations in δ18Oc of two stalagmites from Qal'e Kord (QK) cave in central NW Iran show significant agreement and follow the solar insolation curve at 30°N closely, indicating the fidelity of these records as climate signals. The stalagmites capture millennial-scale Dansgaard/Oeschger stadial and interstadial events (19–25) observed in the North Greenland Ice Core Project (NGRIP). These observations point to the presence of a strong atmospheric teleconnection between the north Atlantic climate and the Middle East region. Variations in δ18Oc from QK cave also agree with the main features of Marine Isotope Stage 5 (MIS5), climate reconstructions from Soreq Cave, Israel, and Sanbao Cave in East Asia. This suggests propagation of a pan-Eurasian climate signal via interplay between changes in solar insolation, strength and position of the mid-latitude Westerly Jet, and strength of the Asian Monsoon. More negative δ18Oc from QK stalagmites are representative of wetter conditions when JJA insolation is at maximum, supporting a hypothesis that winter precipitation should increase in the Mediterranean storm tracks over the interior of West Asia when seasonality is at maximum. This record of water availability from central NW Iran across past glacial cycles suggests precipitation increased with higher solar insolation, an orbital configuration that will not return for another 10,000 years. •Two stalagmites from Iran show changes in climate driven by orbital variations.•High-resolution δ18Oc from stalagmites encompass 73,000–127,000 BP and 6500–7500 BP.•Stalagmites agree extremely closely with NGRIP indicating Atlantic teleconnection.•Agreement with east and west Asian cave records imply pan-Eurasian teleconnection.•Stalagmites show wetter periods appear when insolation was at max configuration

Multi-proxy evidence of millennial climate variability from four Bahamian stalagmites

Northern Hemisphere tropical paleoclimate records support significant hydrologic and climatic changes associated with Dansgaard Oeschger (D/O) events and Heinrich stadials 1 to 6. However, few absolutely dated terrestrial records from the western Atlantic span the last six Heinrich stadials. Here we present geochemical results from four stalagmites collected from a cave in the Bahamas which encompass Heinrich stadials 1 to 6. Absolute geochronometry using U-Th equilibrium series demonstrated that the stalagmites formed between 63.8 to 13.8 kyr before present. The delta (super 13) C and delta (super 18) O values of the calcite showed higher values associated with Heinrich stadials 1-6 and lower values during the D/O interstadial events. The delta (super 18) O value of fluid inclusions from one stalagmite demonstrated minimal variation in the formation water delta (super 18) O value during Heinrich stadials 1 to 3. The Sr/Ca ratios of the calcite are shown to be relatively invariant, while in two of the samples the Mg/Ca ratios tracked the delta (super 13) C values. Increased calcite delta (super 18) O values across Heinrich stadials 1-6 are interpreted as being driven by lower temperatures, as supported by the fluid inclusion results. The two deeper occurring stalagmites demonstrate increased Mg/Ca ratios and delta (super 13) C values during Heinrich stadials 1 and 2 which are interpreted as a signal of reduced flow rates in the epikarst and increased water/rock interactions as a result of increased aridity which potentially occurred across all six Heinrich stadials. The observed reductions in mean annual temperature and amount of precipitation across Heinrich stadials are proposed to be driven by a reduction in sea surface temperatures in the North Atlantic and an expanded Bermuda High. During D/O interstadials, the Bahamas cave records likely indicate warmer and/or wetter climate; however the isotopic shifts are not as significant as the isotopic excursions associated with Heinrich stadials

A new genus for Cirolana troglexuma Botosaneanu &amp; Iliffe, 1997, an anchialine cave dwelling cirolanid isopod (Crustacea, Isopoda, Cirolanidae) from the Bahamas

Cirolana troglexuma Botosaneanu &amp; Iliffe, 1997 is redescribed and a Lucayalana Bruce &amp; Brix, gen. n. established for the species. In total 38 specimens were collected from Hatchet Bay Cave, Eleuthera. Specimens on which previous records of L. troglexuma (from Exuma Cays, Cat Island, and Eleuthera) were based have been re-examined when possible. The diagnostic identifying characters and purported apomorphies for Lucayalana gen. n. are: frontal lamina short, narrow, less than 7% width of labrum, not extending to anterior margin of head; pleonite 3 extending posteriorly to posterior of pleonite 5, laterally overlapping pleonites 4 and 5; ventrally broad, forming a strong ventrally directed blade; pereopods 1–3 merus inferior margin RS not molariform. Mitochondrial COI and 16S loci and the nuclear 18S locus data show that all specimens are the one species. Comparison to additional cirolanid COI sequence data (BOLD, GenBank) show that Lucayalana troglexuma is genetically distinct to all other cirolanid genera with available COI sequences. The single male and females have shared COI (with three females), 16S (eight females) and 18S sequences (two females)

A new genus for Cirolana troglexuma Botosaneanu & Iliffe, 1997, an anchialine cave dwelling cirolanid isopod (Crustacea, Isopoda, Cirolanidae) from the Bahamas

Cirolana troglexuma Botosaneanu & Iliffe, 1997 is redescribed and a Lucayalana Bruce & Brix, gen. n. established for the species. In total 38 specimens were collected from Hatchet Bay Cave, Eleuthera. Specimens on which previous records of L. troglexuma (from Exuma Cays, Cat Island, and Eleuthera) were based have been re-examined when possible. The diagnostic identifying characters and purported apomorphies for Lucayalana gen. n. are: frontal lamina short, narrow, less than 7% width of labrum, not extending to anterior margin of head; pleonite 3 extending posteriorly to posterior of pleonite 5, laterally overlapping pleonites 4 and 5; ventrally broad, forming a strong ventrally directed blade; pereopods 1–3 merus inferior margin RS not molariform. Mitochondrial COI and 16S loci and the nuclear 18S locus data show that all specimens are the one species. Comparison to additional cirolanid COI sequence data (BOLD, GenBank) show that Lucayalana troglexuma is genetically distinct to all other cirolanid genera with available COI sequences. The single male and females have shared COI (with three females), 16S (eight females) and 18S sequences (two females)

A new genus for Cirolana troglexuma Botosaneanu & Iliffe, 1997, an anchialine cave dwelling cirolanid isopod (Crustacea, Isopoda, Cirolanidae) from the Bahamas

Cirolana troglexuma Botosaneanu & Iliffe, 1997 is redescribed and a Lucayalana Bruce & Brix, gen. n. established for the species. In total 38 specimens were collected from Hatchet Bay Cave, Eleuthera. Specimens on which previous records of L. troglexuma (from Exuma Cays, Cat Island, and Eleuthera) were based have been re-examined when possible. The diagnostic identifying characters and purported apomorphies for Lucayalana gen. n. are: frontal lamina short, narrow, less than 7% width of labrum, not extending to anterior margin of head; pleonite 3 extending posteriorly to posterior of pleonite 5, laterally overlapping pleonites 4 and 5; ventrally broad, forming a strong ventrally directed blade; pereopods 1–3 merus inferior margin RS not molariform. Mitochondrial COI and 16S loci and the nuclear 18S locus data show that all specimens are the one species. Comparison to additional cirolanid COI sequence data (BOLD, GenBank) show that Lucayalana troglexuma is genetically distinct to all other cirolanid genera with available COI sequences. The single male and females have shared COI (with three females), 16S (eight females) and 18S sequences (two females)