Coastal Environmental Change and Human Response in Prehistoric Croatia

This study investigates environmental constraints on human settlement over time by researching palaeoenvironmental evidence relevant to the site of Vela Spila, a cave on the Adriatic island of Korčula in Dalmatia, Croatia occupied by humans since ~20 ka BP. This work took place in the framework of the EU twinning project MendTheGap (http://mendthegap.agr.hr/), designed to foster collaboration between partners in Italy, Croatia, and the United Kingdom. This investigation attempts to explain changes in the archaeological record over time, and assess the impact of palaeoenvironmental change on prehistoric humans. The records consulted include sea-level, climate, and palaeolandscape/environment changes since the Last Glacial Maximum. Relative sea level during each settlement period was reconstructed with glacial-hydro-isostatic adjustment models, then cross-checked with nearby sea-level indicators. The submerged palaeogeographic setting of the study was reconstructed with a GIS algorithm to combine available low to mid- resolution bathymetric datasets. Previous reconstructions of this area relied on earlier geophysical models from decades ago and low-resolution bathymetric data only, so this study improves the knowledge of local palaeogeography at different time slices. Climate records, including new oxygen isotope data and sedimentological facies from nearby islands, the Adriatic sea, the Mediterranean, and globally were analysed with the archaeological and palaeoenvironmental records. In addition geomorphological mapping using field surveys and aerial photos of the area was completed to understand the local environment and processes. A field campaign also occurred and several sediment cores were drilled to provide clues about proximal environmental changes. Vela Spila has been intermittently occupied since the late Upper Palaeolithic, beginning at 19.7 cal ka BP through the Bronze Age. Preliminary data on the archaeological stratigraphy show a phase of abandonment following Late Upper Palaeolithic occupation, then intensive use by Mesolithic groups from c. 9.4 cal ka BP to c. 8.4 – 8.0 cal ka BP followed by Neolithic settlement. In this research, the consequences of environmental changes on animals and humans were investigated in a framework of rapidly rising relative sea level, palaeoenvironment, and climate. This study found that during the Palaeolithic, the rate of relative vertical sea-level rise experienced by the cave dwellers was around 3 - 4 mm/a. As a result, these groups saw the coastline moving horizontally inland as much as 5 m/a in the low, flat plains around the island. During this period intense climate oscillations are present in proximal isotope records. Concurrent with the end of the Palaeolithic settlement at ~15 ka BP or soon thereafter, the rate of relative sea-level change increased rapidly to 10-13 mm/a and the cave was abandoned, even while climate stabilized, according to the regional isotope records. The Mesolithic part of the cave sequence reveals massive exploitation of marine resources unlike the Palaeolithic layers, which gradually decreases with time. The exploitation of marine resources could be related to the closer coastline, which shifted from ~8 – 9 km at the start of the recorded Palaeolithic at c. 19.7 cal ka BP, to about 1 km during the early Neolithic settlement at c. 8.4 -8.0 cal ka BP. In addition, Korčula became an island towards the later part of the abandonment phase and hunting grounds in the submerged plains were lost, so these palaeolandscape and climate changes may have contributed to the abandonment of the cave until the Mesolithic, when the relative sea-level rise rate was 7-13 mm/a but shorelines stabilized. The climate transitioned to more stable Mediterranean conditions. The later phases of environmental changes can be detected in sediment cores from Blatsko Polje, which show that a dry phase in the Neolithic preceded the seasonal lake present in the historic period. Prior to that phase, in the early Neolithic or Mesolithic, another seasonal lake phase was also detected