Western Mediterranean climate and environment since Marine Isotope Stage 3: a 50,000-year record from Lake Banyoles, Spain

Jack H Lacey,Blas Valero-Garcés,Melanie J Leng,Jane M Reed,Klaus Reicherter,Nicole Höbig

doi:10.1007/s10933-015-9868-9

Abstract

We present new stable isotope (δ18Ocalcite and δ13Ccalcite) and diatom data from a 67-m sediment core (BAN II) from Lake Banyoles, northeastern Spain. We reassessed the chronology of the sequence by correlating stable isotope data with a shorter U-series-dated record from the lake, confirming a sedimentological offset between the two cores and demonstrating that BAN II spans Marine Isotope Stages (MIS) 3–1. Through comparison with previous records, the multi-proxy data are used to improve understanding of palaeolimnological dynamics and, by inference, western Mediterranean climate and environmental change during the past ca. 50,000 years. Three main zones, defined by isotope and diatom data, correspond to the MIS. The basal zone (MIS 3) is characterised by fluctuating δ18Ocalcite and benthic diatom abundance, indicating a high degree of environmental and climate variability, concomitant with large lake-level changes. During the full glacial (MIS 2), relatively constant δ18Ocalcite and a poorly preserved planktonic-dominated diatom assemblage suggest stability, and intermittently, unusually high lake level. In MIS 1, δ18Ocalcite and δ13Ccalcite initially transition to lower values, recording a pattern of Late Glacial to Holocene change that is similar to other Mediterranean records. This study suggests that Lake Banyoles responds limnologically to changes in the North Atlantic ocean–atmosphere system and provides an important dataset from the Iberian Peninsula, a region in need of longer-term records that can be used to correlate between marine and terrestrial archives, and between the western and eastern Mediterranean.

Highlights

The Iberian Peninsula, located west of the Mediterranean Basin, is a key location for understanding climate connections between the eastern and western Mediterranean (Roberts et al 2008) and interactions with North Atlantic climate dynamics
Calcite is the dominant constituent of the BAN II sediment sequence (Fig. 3; average = 10.1±1.2% as total inorganic carbon (TIC)), which was confirmed by X-Ray Diffraction (XRD) and validated by Scanning Electron Microscopy and Energy-Dispersive X-ray spectroscopy
We presented new stable isotope data (δ18Ocalcite and δ13Ccalcite) from Lake Banyoles, which were combined with previous data (TIC, total organic carbon (TOC), K/Ca) from the same core (Höbig et al 2012) and compared to a shorter core from the lake that provided isotope and pollen records (PérezObiol and Julià 1994; Valero-Garcés et al 1998)

Summary

Introduction

The Iberian Peninsula, located west of the Mediterranean Basin, is a key location for understanding climate connections between the eastern and western Mediterranean (Roberts et al 2008) and interactions with North Atlantic climate dynamics. The understanding of past climate variability across the peninsula itself has improved considerably over the last two decades, employing a range of proxy methods and sources, including sequences from peatbogs (González-Sampériz et al 2006), speleothems (Stoll et al 2013), cave sediment (Fernández et al 2007), and lacustrine sediment (Reed et al 2001; Valero-Garcés et al 2004). Lake Banyoles, a karst lake located northeast of the Iberian Peninsula (Fig. 1), is a rare Iberian example of a relatively deep, fresh lake with a long sediment record, and is an important site for palaeoclimate research in the western Mediterranean. In an early palynological study of the lake sediment core, “La Draga” (named after an adjacent Early Neolithic site excavation), Pérez-Obiol and Julià (1994) showed climatic instability during the Glacial, followed by a rapid transition to the Bølling-Allerød interstadial and the Younger Dryas event, suggesting that the lake responds to North Atlantic climate forcing. Höbig et al (2012) used geochemistry and optical methods on core “BAN II” to identify the impact of HE (H5-H0) in the region

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Conclusion