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Initial radioactive disequilibrium amongst intermediate nuclides of the U decay chains can have a significant impact on the accuracy of U–Pb ages, especially in young samples. For samples that can reasonably be assumed to have attained radioactive equilibrium at the time of analysis, a relatively straightforward correction may be applied. However, in younger materials where this assumption is unreasonable, it is necessary to replace the familiar U–Pb age equations with more complete expressions that account for growth and decay of intermediate nuclides through time. DQPB is software for calculating U–Pb ages while accounting for the effects of radioactive disequilibrium among intermediate nuclides of the U decay chains. The software is written in Python and distributed as both a pure Python package and a stand-alone graphical user interface (GUI) application that integrates with standard Microsoft Excel spreadsheets. The software implements disequilibrium U–Pb equations to compute ages using various approaches, including concordia intercept ages on a Tera–Wasserburg diagram, U–Pb isochron ages, Pb*/U ages based on single aliquots, and 207Pb-corrected ages. While these age-calculation approaches are tailored toward young samples that cannot reasonably be assumed to have attained radioactive equilibrium at the time of analysis, they may also be applied to older materials where disequilibrium is no longer analytically resolvable. The software allows users to implement a variety of regression algorithms based on both classical and robust statistical approaches, compute weighted average ages and construct customisable, publication-ready plots of U–Pb age data. The regression and weighted average algorithms implemented in DQPB may also be applicable to other (i.e. non-U–Pb) geochronological datasets.

Mammoth teeth have been widely investigated using stable-isotopic analysis for paleoenvironmental and paleoecological reconstructions due to their large size and frequent discoveries. Many past investigations sampled the tooth enamel with the “bulk” method, which involves drilling one sample from the occlusal surface to the root for each tooth. Some of the more recent studies applied the “sequential” method, with a sequence of samples drilled following the dominant enamel growth direction to produce a time series of isotopic oscillations that reflects high-resolution environmental changes, as well as changes in mammoth dietary behavior. Although both the bulk and mean sequential δ18O values are expected to represent the averaged signal over the time of tooth formation, it is uncertain whether their paleoenvironmental records were formed during similar periods of time. In this study, we applied both sampling methods (sequential drilling first followed by a thin layer of bulk drilling) on the same enamel ridges of multiple mammoth teeth and compared their respective δ18O values. The results indicated that, in most enamel ridges, the bulk samples have more negative δ18O values compared to the average sequential values, and some of the bulk values even fall outside the range of sequential values. The most likely explanation for the differences is the structure and formation stages of enamel that caused uneven distributions of different seasons recorded in the samples. This finding provides insights into current limitations of the two sampling methods and the applicability of cross-method data comparison from past studies.

In recent years, there has been a growing interest in using archaeological marine mollusc shells as a paleoclimate archive by virtue of their ability to preserve high-resolution paleoclimatic and paleoenvironmental information in multiple biogeochemical proxies. Moreover, valuable information about past environments, human-environmental interactions, and seasonal foraging practices can be obtained via the analysis of marine gastropods from archaeological sites. Rochia nilotica is the most common shell in coral reef ecosystems across the Indo-Pacific Ocean and archaeological shell middens in the Great Barrier Reef (GBR); however, its application as a paleoclimate and paleoenvironment archive to reconstruct the Mid-to-Late Holocene ENSO (El Niño-Southern Oscillation) has not yet been investigated. In this study, we compare temporally successive oxygen isotope and trace element records (δ18O, Mg/Ca, Sr/Ca, and Ba/Ca) in modern R. nilotica shells with instrumental environmental records to test whether we can quantitively reconstruct past environmental parameters. Preliminary results show that modern R. nilotica reliably records environmental factors (e.g. sea surface temperature and salinity) in equilibrium with the surrounding environment at a seasonal scale. These proxies will ultimately be applied to reconstruct localised Mid-to-Late Holocene ENSO records at sub-seasonal scales in the Great Barrier Reef. Results obtained from this ongoing research can be used to compare with climate model simulations to provide a more robust reconstruction of paleo ENSO behavior and offers an opportunity to decipher the long-term shellfish management strategies of Indigenous peoples in the GBR environment to provide a baseline for future marine resource management in the GBR.

Caves are important fossil repositories providing records extending back over million-year timescales. While the physical processes of cave formation are well understood, a more important parameter to studies of palaeontology, palaeoanthropology and archaeology — that of the timing of initial cave development and opening — has proved more difficult to constrain. The Naracoorte Cave Complex (NCC) in southern Australia is a World Heritage site with a rich record of Pleistocene vertebrate fossils, including extinct megafauna, and serves as a natural laboratory in which to investigate these fundamental cave processes. Using U-Th-Pb dating of speleothems we show that the NCC is at least 1.32 million years old, extending the current understanding of initial speleothem formation by ~70% and the antiquity of initial cave development at this site by at least ~20%. We use charcoal and pollen trapped in the same speleothems to place robust constraints on the timing and extent of subsequent cave opening. The findings of this study provide an important means for researchers working on the plethora of fossil-rich sites worldwide to assess the potential upper limit of vertebrate fossil records within caves.

We present the first stable isotope (δ13C and δ18O) speleothem record from continental Croatia retrieved from two coeval stalagmites from Nova Grgosova Cave. U-Th dates constrain the stalagmite growth history from 10 ka to the present, revealing coeval growth between 7.8 and 5.6 ka. We interpret δ18O as an autumn/winter hydrological proxy related to changes of vapor source, precipitation amount, and/or seasonal rainfall distribution, while δ13C predominantly responds to spring/summer vegetation status and soil microbial activity. We identify several centennial to millennial-scale hydroclimate oscillations during this period that result from multiple forcing factors. Along with amount and source effect, it appears that some centennial variations were governed also by seasonal moisture balance. From 9.2 to 8.8 ka BP, the local environmental setting was characterized by enhanced vegetation activity, while during the 8.2 ka event the main feature was a change in precipitation seasonality. The most prominent change, identified in both δ13C records, is a sudden decline of vegetation and soil biological activity around 7.4 ka, indicating a precipitation decrease at a time of maximum plant growth in spring and summer and likely also reduced precipitation in autumn and winter. Although small in magnitude in these speleothems, a peak in δ18O and δ13C values at 4.3–4.1 ka suggests that both summer and winter conditions were substantially drier during the 4.2 ka event, in accordance with increased Mediterranean aridity and consistent with other global climate changes reported at this time. Compared to the present North Atlantic Oscillation (NAO) influence, we assume that millennial Holocene NAO-like variations were persistent through the Holocene via their effect on modifying local/regional air temperature, vapor origin, and inter- and intrannual precipitation distribution. Anthropogenic deforestation, which was the first major human impact on the environment during the Neolithic agricultural revolution, is excluded as a leading factor in δ13C variability since the first sedentary settlements were established further to the east in more arable locations along river valleys. However, the impact of intensive mining around the cave site during the last millennium is evident, with substantial deforestation driving an increase in δ13C.

High-resolution U-Th and 14C dating of two calcite flowstones (RTf: Last Interglacial; RTy: Late Holocene) from the Re Tiberio – Monte Tondo karst system (North Italy) is presented to investigate the palaeoclimate potential of speleothems from gypsum caves. To date, there is a lack of information regarding the dating potential of calcite speleothems that have grown in such gypsum karst environment (e.g. no pseudokarst). High-resolution U-Th dating, aimed at establishing if these speleothems can provide robust radiometric age sequences, is first presented. Although both samples show promise for reliable radiometric dating, about 20% of the ages in the RTf dataset were excluded from the age-model as outliers. These outliers are best explained by post-depositional diagenetic processes affecting the U-Th system rather than anything specific to gypsum karst environment conditions. In contrast, outliers were not detected in the RTy sample, but U-Th analysis was not able to constrain its relatively young age (∼600 years before present, B.P.). Consequently, radiocarbon measurements were undertaken, and combined with the U-Th ages to build an age-model. The latter allowed the estimation of “dead carbon fraction” (DCF), which yields a constant value through time, and a magnitude comparable to other sites where climate is similar to Monte Tondo. Soils were considered the main source of carbon, because bedrock dissolution acted predominantly under open-system conditions, and soil organic matter (SOM) turnover rate appears above average compared to sites studied elsewhere.

The Adriatic Sea, as the northernmost and practically landlocked part of the Mediterranean Sea, is influenced by both Atlantic and Mediterranean air masses, so the isotopic records from coastal cave speleothems are expected to reveal local and regional responses to global climate changes on that bordering region. In this study we present a 365-kyr long composite isotopic record of three speleothems from Modrič Cave located 120 m from the shoreline on the central part of the eastern Adriatic coast. Results of a 4-year monitoring program of the surface and cave microclimate, rain and drip water stable isotope composition and rain and drip intensities, show cave air temperature variations within 1 °C, a relative humidity of 100%, dripwater O and H stable isotopic composition (range 0.4‰) very well buffered against the seasonal rainfall range (6.8‰). Such conditions enable calcite deposition without strong kinetic isotopic disequilibrium effects, as validated by Hendy tests, and give us confidence that the isotopic signal is faithfully recording climate changes. All three speleothems (MOD-31, MOD-32, MOD-33) were active, collected from their growth position, so Holocene signals can be traced in all of them. Within their older parts, U-Th dating reveals the following growth periods: MOD-31 from MIS10 to MIS 7, MOD-32 from MIS 4 to MIS 2, and MOD-33 from MIS 6 to MIS 5. Relatively large 18O and 13C ranges (-8.16‰ – -2.97‰ and -13.11‰ – -1.00‰, respectively) indicate significant environmental changes whose comparison with stable isotope time series of adjacent speleothem records and other regional proxies provides the longest eastern Adriatic speleothem-based record.