A Last Interglacial record of environmental changes from the Sulmona Basin (central Italy)

Highlights

• A multiproxy record from a lacustrine succession covering the MIS5 is presented.

• All proxies show a coherent picture of hydrological and environmental changes.

• The record highlights several dry events within the interglacial.

• Comparison with regional paleoclimate framework shows consistent features.

Abstract

Here we present a multiproxy record (δ¹³C, δ¹⁸O, major and minor element composition, mineralogy, and low-resolution biogenic silica content) from a lacustrine succession in the Sulmona Basin, central Italy. Based on previous tephrochronological constraints and a new ⁴⁰Ar/³⁹Ar dating of a tephra matching the widespread X-6 tephra, the record spans the ca. 129–92 ka period and documents at sub-orbital scale the climatic and environmental changes over the Last Interglacial and its transition to the Last Glacial period. The δ¹⁸O composition is interpreted as a proxy for the amount and seasonality of local precipitation, whereas variations in elemental and mineralogical composition are inferred to reflect climatic-driven changes in clastic sediment input. The observed variations are consistent among the different proxies, and indicate that periods of reduced precipitation were marked by enhanced catchment erosion, probably due to a reduction in vegetation cover. The first part of the Last Interglacial shows the most negative δ¹⁸O values. Comparison with pollen records from the Mediterranean suggests a greater seasonality of the precipitation at this time. At millennial-to-centennial time scales, comparison of the Sulmona record with speleothem δ¹⁸O records from central Italy highlights a highly coherent pattern of hydrological evolution, with enhanced variability and similar events of reduced precipitation consistently recorded by each isotope record. The observed intra-interglacial variability can potentially be linked, within the uncertainties associated with each age model, to similar variations observed in sea-surface temperature records from the Mediterranean and the North Atlantic, suggesting a link between Mediterranean hydrology and North Atlantic temperature and circulation patterns that persists during periods of low ice volume.

Introduction

The climate of the Last Interglacial (LIG), roughly corresponding to marine isotope stage (MIS) 5e and the Eemian interglacial in the European pollen stratigraphy (Govin et al., 2015 and references therein), has many features in common with model projections of future climate, because during this period much of the Earth experienced a climate warmer than present (e.g. Kukla et al., 2002). Although orbital parameters for MIS5e are quite different from that of the Holocene (e.g. Berger and Loutre, 1991), the LIG is a potential analog for projected future global warming and is thus an interesting study case for evaluating the climate and environmental responses during periods characterized by an excess of warmth. From this perspective, of particular interest are intra-interglacial millennial-scale climate changes. Evidence of abrupt climatic variations are well documented in several LIG records from North Atlantic marine sediments and Greenland ice (e.g. Oppo et al., 2001, Oppo et al., 2006, Galaasen et al., 2014, Pol et al., 2014) and some seem to have propagated into the Mediterranean basin (Sáñchez-Goñi et al., 1999, Martrat et al., 2004, Martrat et al., 2014, Sprovieri et al., 2006, Kandiano et al., 2014). Potential expressions of this oceanic driven instability have also been recognized in central Europe (e.g. Sirocko et al., 2005, Seelos and Sirocko, 2007, Seelos et al., 2009), as well as in the Mediterranean region (e.g. Tzedakis et al., 2003, Brauer et al., 2007, Drysdale et al., 2007, Couchoud et al., 2009, Milner et al., 2013, Milner et al., 2016, Regattieri et al., 2014a, Regattieri et al., 2016a, Vogel et al., 2010, Lézine et al., 2010, Zanchetta et al., 2016a). However, the effects of such changes on climate and ecosystems of the European continent are still poorly known and understood (Galaasen et al., 2014, Govin et al., 2015). Identification, correlation and evaluation of the climatic expressions of LIG millennial-scale variability outside the North Atlantic region remain unclear or largely based on postulated temporal phase relations. Addressing these issues requires the compilation of regionally representative, high-resolution and independently dated paleoclimatic records. Lacustrine successions deposited in tectonic basins of the Apennines are capable of fulfilling these requirements (Giaccio et al., 2015a, Giaccio et al., 2015b, Regattieri et al., 2015, Regattieri et al., 2016b, Russo-Ermolli et al., 2010) due to the high sensitivity of the local sediment properties, and particularly of the oxygen stable isotope composition of authigenic carbonates (δ¹⁸O), to hydrological and environmental changes. Moreover, these archives offer the possibility to develop independent age models based on the ⁴⁰Ar/³⁹Ar geochronometer, that can be directly or indirectly applied to the volcanic ash layers (tephra). These tephra layers, deriving from the intense activity of Quaternary peri-Tyrrhenian explosive volcanism, are systematically found in the lacustrine sediments of the Apennine intermountain basins (e.g. Giaccio et al., 2012, Petrosino et al., 2014, Giaccio et al., 2017).

Of the central Italian continental basins, Sulmona has already been recognized as a promising archive. The sedimentary record is underpinned by a robust tephrochronological framework (Giaccio et al., 2012, Giaccio et al., 2013a, Giaccio et al., 2013b), and provides important insights into climate and environmental evolution of the central Mediterranean and the linkages with extra-regional climate variability (Giaccio et al., 2015a, Regattieri et al., 2015, Regattieri et al., 2016b). In particular, the stable isotope profiles (δ¹⁸O and δ¹³C), CaCO₃ content and tephrostratigraphy of the Popoli section (POP hereafter), documenting Early Last Glacial climate fluctuations (from ca. 115 to ca. 90 ka), highlight strong Mediterranean–North Atlantic climate teleconnections as well as the influence of low-latitude circulation patterns (Regattieri et al., 2015). In order to explore the environmental-hydrological changes over the entire early-to-middle MIS 5 (MIS 5e to MIS 5c, ca. 129–92 ka), and in particular the intra-LIG millennial scale variability, in this study we extended through a multiproxy approach (δ¹⁸O and δ¹³C analysis, CaCO₃ content, biogenic silica content, XRF major and minor element composition, XRD-based bulk mineralogy and ⁴⁰Ar/³⁹Ar geochronology) the investigation of the POP section back to ca.129 ka. The results provide a longer and richer multi-proxy record, which allows a detailed reconstruction of local environmental change and give insights on potential relations with the extra-regional millennial-scale variability during the full LIG and at the LIG/Last Glacial transition.