Search

Disentangling the effects of climate and human impact on the long-term evolution of the Earth Critical Zone is crucial to understand the array of its potential responses to the ongoing Global Change. This task requires natural archives from which local information about soil and vegetation can be linked directly to climate parameters. Here we present a high-resolution, well-dated, speleothem multiproxy record from the SW Italian Alps, spanning the last ~10,000 years of the present interglacial (Holocene). We correlate magnetic properties and the carbon stable isotope ratio to soil stability and pedogenesis, whereas the oxygen isotope composition is interpreted as primarily related to precipitation amount, modulated at different timescales by changes in precipitation source and seasonality. During the 9.7-2.8 ka period, when anthropic pressure over the catchment was scarce, intervals of enhanced soil erosion are related to climate-driven vegetation contractions and occurred during drier periods. Immediately following the onset of the Iron Age (ca. 2.8 ka), by contrast, periods of enhanced soil erosion coincided with a wetter climate. We propose that the observed changes in the soil response to climate forcing were related to early anthropogenic manipulations of Earth's surface, which made the ECZ more sensitive to climate oscillations. [ABSTRACT FROM AUTHOR]

The period corresponding to Marine Isotope Stages 9 (MIS 9) offers the opportunity to study orbital and sub-orbital scale climate variability under boundary conditions different from those of better studied intervals such as the Holocene and the Last Interglacial. Yet, it is poorly represented in independently-dated continental archives around the Mediterranean Region. Here, we present a speleothem stable isotope record (δ 18 O and δ13 C) from the Former Yugoslavian Republic of Macedonia (F.Y.R.O.M., southern Balkans), which consists of two periods of growth broadly covering the ca. 332 to 292 ka and the ca. 264 to 248 ka intervals (MIS 9e-b and late MIS 8). We interpret the speleothem δ 18 O as mostly related to regional hydrology, with variations that can be interpreted as due to changes in rainfall amount, with higher/lower values associated to drier/wetter condition. This interpretation is corroborated by a change in mineralogical composition between aragonite and calcite at ca. 328 ka, which marks increasing precipitation at the onset of MIS 9 and occurs within a trend of decreasing δ 18 O values. Also the comparison with the multiproxy climate record available from the nearby Lake Ohrid seems to support the proposed interpretation. The MIS 9e interglacial appears to be characterized by wettest conditions between ca. 326 and 321 ka, i.e. lasting ca. 5 kyr. Decreasing precipitation and enhanced millennial scale variability matches the glacial inception (MIS9 d to b), with drier events at ca. 319 ka (ca. 2 kyr long) and 310 ka (ca. 1 kyr long), and a major rainfall reduction between 306 and 298 ka. The latter is followed by a prominent wetter period between 298 and 295 ka, for which carbon data values suggest high infiltration rate. Rainfall decreases again after 295 ka, and remain low until the growth interruption at ca. 292 ka. Resumption of the growth and progressive soil development, expressed by the carbon isotope record, occurred during the late part of MIS 8. Despite the rather high temporal uncertainty (average 6 ka), the speleothem hydrological record complements the environmental information provided by the Lake Ohrid record and also fits well to the framework of regional and extra-regional variability, showing similarities with pollen records from southern and western Europe, both at orbital and at sub-orbital time scale. [ABSTRACT FROM AUTHOR]

Past orbital analogues to the current interglacial, such as Marine Isotope Stage 19c (MIS 19c, ca. 800 ka), can provide reliable reference intervals for evaluating the timing and the duration of the Holocene and factors inherent in its climatic progression. Here we present the first high-resolution paleoclimatic record for MIS 19 anchored to a high-precision 40Ar/39Ar chronology, thus fully independent of any a priori assumptions on the orbital mechanisms underlying the climatic changes. It is based on the oxygen isotope compositions of Italian lake sediments showing orbital- to millennial-scale hydrological variability over the Mediterranean between 810 and 750 ka. Our record indicates that the MIS 19c interglacial lasted 10.8 ± 3.7 k.y., comparable to the time elapsed since the onset of the Holocene, and that the orbital configuration at the time of the following glacial inception was very similar to the present one. By analogy, the current interglacial should be close to its end. However, greenhouse gas concentrations at the time of the MIS 19 glacial inception were significantly lower than those of the late Holocene, suggesting that the current interglacial could have already been prolonged by the progressive increase of the greenhouse gases since 8-6 ka, possibly due to early anthropogenic disturbance of vegetation. [ABSTRACT FROM AUTHOR]

The stable isotope composition of living and of Holocene Mytilidae shells was measured in the area of Camarones (Chubut, Argentina). The most striking results were the high δ18O values measured in samples older than ca. 6.1 cal ka BP. In the younger samples, the δ18O values remained substantially stable and similar to those of living specimens. Analysis of the data revealed the possibility for this isotopic shift to be driven mainly by changes in temperature probably accompanied by minor changes in salinity, suggesting cooler seawater before 6.1 cal ka BP, with a maximum possible temperature shift of ca. 5 °C. A possible explanation of this change can be related to a northward position of the confluence zone of the Falkland and Brazilian currents. This is consistent with the data obtained in marine cores, which indicate a northerly position of the confluence in the first half of the Holocene. Our data are also in line with the changes in wind strength and position of the Southern Westerlies Wind, as reconstructed in terrestrial proxies from the Southernmost Patagonia region. [ABSTRACT FROM AUTHOR]

During the Bronze and Iron Age, Sardinia was home of one of the most technologically advanced Mediterranean societies (the Nuragic culture). Given its key geographical location, the island was also the fulcrum of deep cultural exchanges. Toward the end of the Iron Age, Phoenicians, and especially Carthaginians and Romans, massively frequented Sardinia for different purposes. This marks an important cultural transition for the region, as the ancient Nuragic-related society terminated. At the same time, this impacted the subsistence and land use practices. Together with middle to late Holocene climate changes, the novel anthropic activities had a pivotal role in shaping the landscape around the island. However, high resolution climate and environmental records for these culturally important phases are still lacking in Sardinia. Thus, this paper explores palaeoenvironmental changes from the Bronze Age to post Iron Ages times by using carbonate speleothems from Suttaterra de Sarpis Cave (Urzulei, central east Sardinia), strategically located nearby the Or Murales Nuragic Village. U–Th ages (n = 20) indicate that five stalagmites comprehensively span the last ∼7000 years. Peculiarly, they all show an evident stratigraphic discontinuity. Age models attest that hiatuses can be at times associated with the discontinuities, spanning periods of ∼1200 to ∼200 years. Importantly, the discontinuities occurred from the Late Iron Age to the Roman period. Based on fabric observations, trace elements and δ13C- δ18O analyses, the discontinuities are primarily attributed to a progressive change of land use above the cave. We suppose that deforestation aimed to clearance for agriculture and livestock practices probably was the most impacting factor for infiltration dynamics and soil state, thus affecting the studied speleothems, although archaeological and historical data are absent for the specific study area. Instead, this is in line with the cultural transition occurring in Sardinia toward the end of the Iron Age, with novel agricultural practices imported by the overseas populations. The anthropic disturbance to the millennial-long karst equilibrium possibly overprinted the response of speleothem proxies to climate oscillations, although future higher resolution analyses are necessary to better investigate the evolution of climate during the Holocene as well as its role in the development of ancient civilizations. Indeed, this is the first speleothem-based Holocene palaeoenvironmental reconstruction accomplished in Sardinia. Considering the paucity of natural lakes in this key location, speleothems here demonstrate their potential in exploring human-driven palaeoenvironmental changes during times of cultural transitions within the Mediterranean context. • The first Holocene speleothem paleoenvironmental record from Sardinia (Italy). • Changes in geochemical and physical speleothems' properties point to variation of land use. • Land use variation is connected to cultural shifts during intra- and post-Nuragic period. [ABSTRACT FROM AUTHOR]

Speleothems are potentially excellent archives of the Earth's magnetic field, capable of recording its past variations. Their characteristics, such as the continuity of the record, the possibility to be easily dated, the almost instantaneous remanence acquisition and the high time-resolution make them potentially unique high-quality Paleosecular Variation (PSV) recorders. Nevertheless, speleothems are commonly characterized by low magnetic intensities, which often limits their resolution. Here we present a paleomagnetic study performed on two cores from a flowstone from the Rio Martino Cave (Western Alps, Italy). U/Th dating indicates that the flowstone's deposition covers almost the entire Holocene, spanning the period ca. 0.5–9.0 ka, while an estimation of its mean growth rate is around 1 mm per 15 years. The flowstone is composed of columnar calcite, characterized by a highly magnetic detrital content from meta-ophiolites in the cave's catchment. This favorable geological context results in an intense magnetic signal that permits the preparation and measurement of thin (∼3 mm depth equivalent) samples, each representing around 45 yr. The Characteristic Remanent Magnetization (ChRM), isolated after systematic stepwise Alternating Field demagnetization, is well defined, with Maximum Angular Deviation (MAD) generally lower than 10°. Paleomagnetic directional data allow the reconstruction of the PSV path during the Holocene for the area. Comparison of the new data with archeomagnetic data from Italian archeological and volcanic records and using the predictions of the SHA.DIF.14k and pfm9k.1a global geomagnetic field models shows that the Rio Martino flowstone represents an excellent recorder of the Earth's magnetic field during the last 9,000 years. Our high resolution paleomagnetic record, anchored by a high-quality chronology, provides promising data both for the detection of short term geomagnetic field variations and for complementing existing regional PSV curves for the prehistoric period, for which well-dated data are still scarce. [ABSTRACT FROM AUTHOR]

Numerous palaeoenvironmental and archaeological studies from southern Arabia (Yemen and Oman) have revealed strong relations between phases of human settlements and climate change linked to the Indian monsoon system. Analyses on speleothems, cave fills, lacustrine deposits and palaeo-mangroves have shown that during the Early to Mid-Holocene, a humid Optimum culminated around 9000–8000 cal BP. New results on inland speleothems and cave sediments from the Jebel Qara (southern Oman) are crucial in our depiction of Early and Mid-Holocene climatic evolution and cultural dynamics of the region. These aspects are discussed here, based on new archaeological surveys, excavations, geoarchaeological and micromorphological studies, aiming to better understand connections with Terminal Pleistocene and Early Holocene autochthonous cultures of southern Arabia. Our results suggest that the final Pleistocene was marked by strong aridity, which promoted a widespread thermoclastism within rock shelter and deposition of aeolian sand; in contrast, the transition towards the Holocene is marked (since c. 12,000 cal BP) by a progressive increasing in environmental humidity, which permitted the formation of thick strata of peridesert loess. After this phase, the environmental humidity of the Jebel increased and permitted the existence of a large community of land snails; the latter were exploited by Early Holocene hunter–gatherers who lived in the rock shelters between c. 10,500–9500 cal BP and left consistent accumulations of land shells ( escargotières ). The maximum of Holocene humidity was reached between 9000 and 8000 cal BP; regional aquifer were recharged and the deposition of calcareous tufa at the entrance of caves started, lasting up to c. 4500 cal BP. C and O stable isotopes from calcareous tufa highlights, in accordance with several regional records, the progressive decline of the intensity of the Indian Ocean monsoon and the transition towards arid conditions. In this phase, the area was abandoned and archaeological communities possibly relocated along the coast of central and southern Oman, where they exploited the mangrove environment. [ABSTRACT FROM AUTHOR]