10:30am - 10:45am
Ernesto Cave, northern Italy: a candidate for Global Boundary Stratotype Section and Point for the Anthropocene Series
1School of Environmental and Life Sciences, The University of Newcastle, Australia; 2Museo delle Scienze, Trento, Italy; 3School of Geography, Earth and Environmental Sciences, University of Birmingham, UK; 4Lancaster Environnent Centre, Lancaster University, UK; 5German Federal Office for Radiation Protection, Berlin, Germany
Ernesto Cave (Trentino, northern Italy) is one of the most studied and monitored caves worldwide, with over 30 research papers published so far. The ubiquitous presence of visible, fluorescent and chemical annual laminae facilitates precise calendar-year resolution and robust correlation of proxy signals between different stalagmites.
For almost 10 years Grotta di Ernesto has also been considered as a candidate for a Global Boundary Stratotype Section and Point (GSSP) for the Anthropocene Series, based on the presence of several anthropocene markers including lamina thickness, radiocarbon, sulphur concentration and sulphur isotopes.
In particular, by comparing the multiproxy series from stalagmites ER77 and ER78, two major change points clearly related to anthropocene activities have been identified. The year 1840 CE corresponds to a change in calcite fabric from microcrystalline and impurity-rich to clear compact columnar; a sudden decrease in calcite fluorescence; an increase in lamina thickness; and a sharp increase in δ13C values. This date marks the beginning of industrialization in Europe and the end of the Little Ice Age in the Italian Alps triggered by the steady increase in the surface mean annual temperatures. The year 1960 CE corresponds to the proposed position of the GSSP. In ER77, this is based on the deflection point in the 14C activity curve, whereas in ER78 this year corresponds to the increase in annual growth rate and S concentration, and the following shift towards depleted δ34S–SO4 that suggests an additional source of sulphur originating from industrial pollution.
Any formal designation of a new geological division has to adhere to the processes of the International Stratigraphic Commission. In recent years, ice core and speleothem archives have been used to mark the GSSPs for the base and internal divisions of the Holocene Epoch. The Anthropocene Working Group (AWG) has voted by a large majority to establish a GSSP in an archive corresponding to the mid-20th century, coinciding with the “Great Acceleration” of indicators of human impact. This aligns with the view of Earth system scientists that the Earth is no longer behaving in the Holocene mode. The AWG is compiling proxy data on 12 archives that could represent potential stratotypes including various marine and lacustrine sediment cores, corals, Ernesto speleothems and a peat and an anthropogenic archive. Later in 2022, summaries will be published and AWG members will vote for their preferred choice which in turn will be considered by higher-level committees within the International Stratigraphic Commission.
10:45am - 11:00am
Stratigraphic discontinuities in underground deposits vs cultural changes at the surface: a case study from the Bronze/Iron Age (Sardinia, Italy)
1University of Parma, Italy; 2Xi’an Jiaotong University, China; 3Istituto di Geoscienze e Georisorse, IGG-CNR, Pisa, Italy; 4University of Sassari, Italy; 5University of Cagliari, Italy; 6University of Bologna, Italy
During the Bronze and Early Iron Age, the Island of Sardinia (Italy) was home of the so-called Nuragic Civilization (~1700-500 BC). Considering the huge cultural and architectonical heritage related to this period, Nuragics were among the most technologically advanced populations around the Mediterranean. Yet, there is no solid theory regarding the social-cultural evolution and termination of such an advanced culture, which comprehensively considers a combination of socio-cultural-political-historical events and climate and environmental changes.
This work presents the first speleothem-based Holocene environmental reconstruction from Sardinia, by reporting the preliminary U-Th dating, stable isotopes (δ18O-δ13C), raman spectroscopy, and petrographic results from 5 stalagmites. Samples were recovered in Suttaterra de Sarpis Cave (Urzulei), which is strategically located less than 1 km from Or Murales Nuragic village. The flat surface above the cave was an ideal location for ancient anthropic activities, such as livestock, agriculture and/or deforesting. In general, the whole area was densely settled and exploited during Nuragic times, as attested by other nearby important archaeological sites.
U-Th ages (n=20 in total) indicate that the studied stalagmites comprehensively span the last ~7000 years. Peculiarly, they all show an evident stratigraphic discontinuity: while the bottom appears brownish, the top is sensibly less dark, whitish in color. Such a marked change is also visible at micro scale in thin sections. δ18O-δ13C and raman spectroscopy results also highlight differences in the portions above and below the discontinuities. Age models attest that hiatuses can be associated with the discontinuities, with lengths from ~1200 to ~200 years. Importantly, the discontinuities occurred, within age uncertainties, toward the end of the Nuragic era, when Sardinia had first strict contacts with Phoenicians (a phase called “Orientalization”, ~700-600 BC), was then invaded by Punics (~500 BC) and later controlled by Romans. We here start to investigate the meaning of such a petrographic and geochemical discontinuity. Is it related to climate? Were different uses of the land above the cave, boosted by the arrival of new cultures in Sardinia, playing a role? Could climate and anthropic-cultural factors be interconnected? We address these questions by discussing our results within the archaeological framework of the “Nuragic” period in Sardinia and the Holocene palaeoclimate of the Mediterranean area.
11:00am - 11:15am
A speleothem-based reconstruction of Early Holocene the climate-environmental-human nexus in the Fertile Crescent
1Dipartimento di Scienze delle Terra “A. Desio”, Università degli Studi di Milano, I-20133 Milano; 2Istituto di Geoscienze e Georisorse, IGG-CNR, Via Moruzzi 1, 56126 Pisa, Italy; 3Istituto Nazionale di Geofisica e Vulcanologia INGV, 56126, Pisa Italy Italy; 4Department of Resource Management and Geography, University of Melbourne, Victoria 3010, Australia; 5Dipartimento di Scienze della Terra, Università di Pisa, 56126 Pisa, Italy; 6School of Earth Sciences, University of Melbourne, Victoria 3010 Australia; 7Dipartimento di Scienze dell'Antichità, Università di Roma Sapienza, 00185 Roma, Italy; 8Dipartimento di Studi Umanistici e del Patrimonio Culturale, Università di Udine, 33100 Udine, Italy
At the beginning of Holocene, the Fertile Crescent (FC) – and particularly the Kurdistan Region of Iraq (KRI)– was the scenario of several fundamental cultural events such as the origin of agriculture, the beginning of urbanization, and the formation of the first state entities. The role played by climate and environmental changes on these cultural processes is highly debated, but local, continuous, and well-dated palaeoclimatic records are still scarce. In this contribution, we present the results of a palaeoclimatological and palaeoenvironmental investigation in this area, derived from a speleothem covering the Early Holocene Early (ca. 11 to 7.3 ka), and encompassing the Neolithic to Early Chalcolithic periods. The speleothem record shows multi-centennial hydroclimatic fluctuations that can be related to changes in the intensity of the Siberian High (SH). The SH affected regional synoptic conditions, influencing the amount of winter precipitation, and modulating the length of wet season. The comparison of our data with the local archaeological record suggests a link between these hydroclimatic fluctuations with changes in settlement patterns and a re-organization of subsistence strategies, particularly to the exploitation of water resources
11:15am - 11:45am
SHAKING UP OUR HUMAN FAMILY TREE: U-PB DATING SPELEOTHEMS FROM THE CRADLE OF HUMANKIND, SOUTH AFRICA
1University of Cape Town, South Africa; 2Human Evolution Research Institute
The Cradle of Humankind (Cradle) in South Africa is home to a rich collection of early human (hominin) fossils, preserved in dolomite caves. Flowstones are ubiquitous features at all the fossil bearing cave sites. These flowstone serve the dual purpose of providing ages for the fossilferous sediments sandwiched between them (via uranium-lead dating) and as indicators of past climate regimes by their presence alone, being associated with increased effective precipitation. Massive flowstones of several meters thick are not uncommon and hint at prolonged periods of significantly increased precipitation. Uranium-lead (U-Pb) dating of cave carbonates has reached a level of maturity where it can be applied with ease and precision. Flowstones from eight caves across the Cradle has produced a total of twenty eight U-Pb ages. To solve the problem of necessarily large uncertainties on individual ages, a kernel density estimate is used to sum together the U-Pb age data into a single record of flowstone growth intervals (FGIs). This record spans from 3.2 – 1.3 Ma, with four major FGIs identified, with flowstone forming in at least two caves during the each time interval. These intervals are interpreted as major wet phases, during which caves were most likely sealed closed and not receiving sediments/bones from outside, allowing for massive flowstone development. The interceding times are interpreted as drier phases, during which the fossiliferous sediments accumulated in the caves. These new data suggest that these fossil bearing deposits carry an inherent ‘dry phase’ bias, implying that the South African hominin and faunal record is only sampling these drier intervals and that large periods of time (during wetter phases) are unrepresented in the fossil record. While the periods of cave closure leave temporal gaps in the South African fossil record, the flowstones themselves provide valuable insights into both local and pan-African climate variability.