Papers by Russell Drysdale
Speleothems are usually considered as one of the most amenable palaeoclimate archives for U-serie... more Speleothems are usually considered as one of the most amenable palaeoclimate archives for U-series dating. A number of studies in recent years, however, report cases of diagenetic alteration which compromises the use of U-series systematics in speleothems, resulting in inaccurate U-Th ages. Here we present the results of a high-resolution U-Th dating study of a stalagmite (CC26) from Corchia Cave in Italy where we document a number of departures from an otherwise well-defined age-depth model, and explore potential causes for these outliers. Unlike examples illustrated in previous studies, CC26 contains no visible evidence of neomorphism, and appears, at least superficially, ideally suited to dating. Good reproducibility obtained between multi-aliquot U-Th analyses removes any possibility of analytical issues contributing to these outliers. Furthermore, replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence, implying very localized open-system behavior. Uranium loss is suggested as a causative mechanism on account of the fact that all the outliers are older than their assumed true age. A limited number of micro-voids were observed under micro-CT analyses, and it is proposed that these were pathways for U loss. Uranium-loss modelling allows us to constrain the possible timing of diagenetic alteration and indicates that the precursor for the outlier with the largest age discrepancy (309%) must have been aragonite. This study indicates that visibly unaltered speleothems may still contain small domains that have experienced post-depositional alteration. Such " cryptic " diagenesis, as recorded in this stalagmite, has implications for the constancy of accuracy of the U-series dating technique, and suggests a need for careful examination of speleothems prior to dating, particularly in low-resolution U-Th studies.
PALAEOCLIMATIC RECONSTRUCTIONS OF THE PERI-ADRIATIC AREA THROUGH SPELEOTHEMS: FIRST RESULTS
- In ... more PALAEOCLIMATIC RECONSTRUCTIONS OF THE PERI-ADRIATIC AREA THROUGH SPELEOTHEMS: FIRST RESULTS
- In the framework of a PhD thesis at the University of Bologna and the University of Savoie (France), and in
collaboration with the University of Melbourne (Australia), an ambitious scientific project is being carried out
with the aim of finding palaeoclimatic records in speleothems sampled in caves of Italy and the Dinaric Karst.
In this first sampling phase, thanks to the collaboration with local cavers, already broken stalagmites and
flowstones have been taken in caves of Apulia, Emilia-Romagna, Trieste, Slovenia, and Bosnia Erzegovina. The
samples have been cut along their length and polished. The bottom and top of the most promising samples (with
well visible growth layers, clean primary calcite, without evident signs of recrystallization) has been dated to
get their age of growth. The following microdrill sampling has allowed to take powders to be analysed at Mass
Spectrometer for the stable isotopes of oxygen and carbon. These studies will allow to reconstruct the climate of
the past in the areas of these caves, delivering a valid contribution to the palaeoclimate studies in the Central
Mediterranean.
International Journal of Speleology, 2008
ABSTRACT The Alpine region currently experiences complex climatic conditions (Efthymidias et al.,... more ABSTRACT The Alpine region currently experiences complex climatic conditions (Efthymidias et al., 2007). Such a complexity is also apparent during the Holocene, as revealed by the isotopic composition of speleothems (e.g. Spötl et al., 2010). However, virtually no speleothem data are available from the western Alps, which are dominated by North Atlantic synoptic systems. With this in mind, several flowstone cores were retrieved in Rio Martino Cave (Piemonte, Northern Italy, ca. 1530 m asl). A large part of the cave's catchment was substantially glaciated until the end of the Younger Dryas. U/Th dating of three different flowstones indicates that deposition started at the beginning of the Holocene and covered a thick deposit of cemented sand and gravels probably related to the last deglaciation. The combined δ18O record of different flowstones shows substantial variability through the Holocene, both on millennial and century time scales. Relatively low δ18O values last until ca. 6 ka. From 6 to 3 ka, the δ18O increases gradually before decreasing again from 3 ka to the present. This long-term trend may be related to changes in the seasonal patterns of precipitation, as suggested for the lake level record at Ledro (Magny et al., 2012). Superimposed on this trend there are several short-term oscillations which may reflect alternating periods of drier and wetter conditions. Some of these episodes are also in agreement with changes documented at Ledro. Efthymidias D., et al., 2007. Influence of large-scale atmospheric circulation on climate variability in the Greater Alpine Region of Europe. Journal of Geophysical Research, 112, D12104. Magny M. et al., 2012. Holocene palaeohydrological changes in the northern Mediterranean borderlands as reflected by the lake-level record of Lake Ledro, northeastern Italy. Quaternary Research, 77, 382-396 Spötl, C., et al., 2010. Humid climate during deposition of sapropel 1 in the Mediterranean Sea: Assessing the influence on the Alps. Global and Planetary Change 71, 242-248.
ABSTRACT Antro del Corchia (Corchia Cave) is a large cave located in the Alpi Apuane karst of nor... more ABSTRACT Antro del Corchia (Corchia Cave) is a large cave located in the Alpi Apuane karst of northern Tuscany, Italy. The cave receives most of its recharge from frontal systems crossing southwestern Europe and western Mediterranean, making the site sensitive to changes in ocean and atmospheric conditions in the North Atlantic. Parts of the cave are rich in speleothems. A suite of stalagmites, flowstones and subaqueous mounds has been sampled to investigate regional palaeoclimate. Stable oxygen and carbon isotopes time series produced from these speleothems, anchored in time using U-Th, U-U and U-Pb isotopic dating, preserve evidence for regional rainfall and temperature changes over millennial and glacial-interglacial timescales that can be linked via the marine-core record to North Atlantic palaeoclimate. A single speleothem core, recovered from a subaqueous mound in the cave, preserves the last 11 glacial-interglacial cycles, constituting a rare and seemingly continuous palaeoclimate record spanning the last 960 ka. More detailed palaeoclimate reconstructions are emerging from the faster growing stalagmites from the cave. The entire speleothem stack provides a means for establishing the timing of glacial terminations and inceptions.
Geografia Fisica e Dinamica Quaternaria, 2012
In this work we present the results of a stratigraphic and lithologic study of a flowstone from T... more In this work we present the results of a stratigraphic and lithologic study of a flowstone from Tana che Urla Cave, Apuan Alps (central Italy) which grew intermittently between ca. 160 and 8 ka. The studied succession consists of an alternation of two different lithofacies (Lf-A, Lf-B): a brown, detrital-rich (Lf-A) and a white, inclusion-poor calcite (Lf-B). Using available growth rate data, the difference between the two lithofacies is thought to be the result of different amounts of meteoric precipitation, with Lf-A related to low growth rates at times of ...
Relatively few radiometrically dated records are available for the central Mediterranean spanning... more Relatively few radiometrically dated records are available for the central Mediterranean spanning the marine oxygen isotope stage 6-5 (MIS 6-5) transition and the first part of the Last Interglacial. Two flowstone cores from Tana che Urla Cave (TCU, central Italy), constrained by 19 U/Th ages, preserve an interval of continuous speleothem deposition between ca. 159 and 121 ka. A multiproxy record (δ 18 O, δ 13 C, growth rate and petrographic changes) obtained from this flowstone preserves significant regional-scale hydrological changes through the glacial/interglacial transition and multi-centennial variability (interpreted as alternations between wetter and drier periods) within both glacial and interglacial stages. The glacial stage shows a wetter period between ca. 154 and 152 ka, while the early to middle Last Interglacial period shows several drying events at ca. 129, 126 and 122 ka, which can be placed in the wider context of climatic instability emerging from North Atlantic marine and NW European terrestrial records. The TCU record also provides important insights into the evolution of local environmental conditions (i.e. soil development) in response to regional and global-scale climate events.
Quaternary Science Reviews, 2009
A stalagmite (BDinf) recovered from an archaeological cave (Bourgeois–Delaunay, La Chaise de Vout... more A stalagmite (BDinf) recovered from an archaeological cave (Bourgeois–Delaunay, La Chaise de Vouthon) in SW France provides a rare, high-resolution, precisely dated continental palaeoclimate record covering the warmest part of the Last Interglacial (128±1–121±1ka). The growth interval spans the pluvial period recorded in Soreq and Peqiin Cave speleothems (during sapropel event S5), suggesting that the eastern Mediterranean and western Europe
Science, 2009
Variations in the intensity of high-latitude Northern Hemisphere summer insolation, driven largel... more Variations in the intensity of high-latitude Northern Hemisphere summer insolation, driven largely by precession of the equinoxes, are widely thought to control the timing of Late Pleistocene glacial terminations. However, recently it has been suggested that changes in Earth's obliquity may be a more important mechanism. We present a new speleothem-based North Atlantic marine chronology that shows that the penultimate glacial termination (Termination II) commenced 141,000 +/- 2500 years before the present, too early to be explained by Northern Hemisphere summer insolation but consistent with changes in Earth's obliquity. Our record reveals that Terminations I and II are separated by three obliquity cycles and that they started at near-identical obliquity phases.
Quaternary Science Reviews, 2013
We present a precisely dated, multi-proxy stalagmite record from Liang Luar Cave, Flores (southea... more We present a precisely dated, multi-proxy stalagmite record from Liang Luar Cave, Flores (southeast Indonesia) that reveals a rapid increase in Indonesian monsoon rainfall at w9.5 ka. A "ramp-fitting" method for detecting statistically significant inflections in a time-series was applied to the stalagmite d 18 O, Mg/Ca, and Sr/Ca profiles to quantify the precise timing and magnitude of an abrupt increase in monsoon strength over a period of w350 years. Previously published lake-level records from the monsoon-affected Australian interior show a sudden intensification of the Australian monsoon at w14 ka. However, our records indicate that monsoon intensification in Flores occured w4e5 kyr later. The timing of the monsoon shift in Flores is synchronous with the rapid expansion of rainforest in northeast Australia and regional freshening of the southern Makassar Strait which, under present-day conditions, is sensitive to monsoon variability. The freshening of southern Makassar was coeval with an abrupt w1.5 C cooling in the upper thermocline of the Timor Sea w9.5 ka, indicative of reduced surface heat transport by the Indonesian Throughflow (ITF) when the Java Sea opened during postglacial sea-level rise. This suggests that the abrupt increase in monsoon rainfall on Flores was not due to a change in the ITF e because a decrease in rainfall would be expected to accompany cooler local sea surface temperatures (SSTs) e but rather by the sudden increase in ocean surface area and/or temperature in the monsoon source region as the Sunda Shelf flooded during deglaciation. We propose that it was the abrupt intensification of the monsoon through the late deglaciation that maintained the subsequent structure of the ITF following the flooding of the Sunda Shelf at w9.5 ka.
Quaternary Science Reviews, 2007
Quaternary Science Reviews, 2011
A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central I... more A stratigraphic and chronological study of the upper level of Renella Cave (Apuan Alps, Central Italy) reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8.2 and 7.1 ka. This layer, which represents a period of enhanced cave flooding, is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby Corchia Cave, interpreted to have resulted from an increase in local precipitation. These data confirm that during this period of time the region experienced relatively wetter conditions, including an increase in high-magnitude events capable of invading the higher passages of Renella Cave. The timing of the clastic phase occurred when the Eastern Mediterranean experienced deposition of sapropel layer S1, which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the Nile in response to increased monsoon intensity in northern equatorial Africa. Recent estimates suggest that S1 may have lasted from ca 10.8 to ca 6.1 ka cal BP. Combined evidence from Renella and Corchia Cave indicates that the period corresponding to the wettest phase in the Apuan Alps was much shorter than this, and suggests that there is no straightforward connection between increased advection of water vapour from the Atlantic between 8.2 and 7.1 ka, as recorded in the Corchia and Renella records, and monsoon-driven enhancement of Nile discharge and S1 deposition in the eastern Mediterranean.
Quaternary Science Reviews, 2013
Geochemical and physical changes along the growth axis of speleothems are controlled by climate a... more Geochemical and physical changes along the growth axis of speleothems are controlled by climate as well as the dynamics of the host karst system. Discriminating between the two is one of the major challenges in assembling robust cave palaeoclimate records. Overcoming this dilemma may be achieved by investigating multiple properties from two or more speleothems from the same cave, spanning the same time interval. In this study, we use high-resolution stable oxygen and carbon isotope (d 13 C and d 18 O), morphological and petrographic data from two calcite stalagmites (SV1 and SV7) from Grotta Savi,
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Papers by Russell Drysdale
- In the framework of a PhD thesis at the University of Bologna and the University of Savoie (France), and in
collaboration with the University of Melbourne (Australia), an ambitious scientific project is being carried out
with the aim of finding palaeoclimatic records in speleothems sampled in caves of Italy and the Dinaric Karst.
In this first sampling phase, thanks to the collaboration with local cavers, already broken stalagmites and
flowstones have been taken in caves of Apulia, Emilia-Romagna, Trieste, Slovenia, and Bosnia Erzegovina. The
samples have been cut along their length and polished. The bottom and top of the most promising samples (with
well visible growth layers, clean primary calcite, without evident signs of recrystallization) has been dated to
get their age of growth. The following microdrill sampling has allowed to take powders to be analysed at Mass
Spectrometer for the stable isotopes of oxygen and carbon. These studies will allow to reconstruct the climate of
the past in the areas of these caves, delivering a valid contribution to the palaeoclimate studies in the Central
Mediterranean.
- In the framework of a PhD thesis at the University of Bologna and the University of Savoie (France), and in
collaboration with the University of Melbourne (Australia), an ambitious scientific project is being carried out
with the aim of finding palaeoclimatic records in speleothems sampled in caves of Italy and the Dinaric Karst.
In this first sampling phase, thanks to the collaboration with local cavers, already broken stalagmites and
flowstones have been taken in caves of Apulia, Emilia-Romagna, Trieste, Slovenia, and Bosnia Erzegovina. The
samples have been cut along their length and polished. The bottom and top of the most promising samples (with
well visible growth layers, clean primary calcite, without evident signs of recrystallization) has been dated to
get their age of growth. The following microdrill sampling has allowed to take powders to be analysed at Mass
Spectrometer for the stable isotopes of oxygen and carbon. These studies will allow to reconstruct the climate of
the past in the areas of these caves, delivering a valid contribution to the palaeoclimate studies in the Central
Mediterranean.