Morphological changes associated with the drier and windier LIA in the Danube delta

Abstract

This study reports on the Letea dune field - the largest of this type in the Danube delta - and on the Sărăturile beach ridge plain, which both displayed the largest morphodynamics during the Little Ice Age (LIA: 1450 – 1850). The reconstructed morphodynamics of the two deltaic units are based on GPR scanning of the marine and aeolian structures and OSL dating, which aimed to track the sea level curve, and the aeolian activity archived in these coastal barriers. The earliest aeolian features preserved in the modern Letea barrier landscape appeared ca. 2400 years ago as shore parallel foredunes and continued to form as such until ca. 770 years ago. Still, under the constant predominantly northern winds, they have been reworked into an extensive dunefield mostly between ca. 1500 and 1800 AD. The dunefield is composed of four large parabolic complexes containing parabolic dunes, precipitation ridges and remnant knobs as common morphotypes. Intense dune activity during LIA was spurred by a significant river flooding during the 14th century AD, which caused the displacement of the Chilia distributary position and the subsequent beach ridge plain and dune truncation. High rates of dune mobility were maintained by the cumulative effect of the drier and windier climatic conditions, probably slightly lower sea level of the Black Sea during the Little Ice Age, and local deforestation during the Ottoman occupation of the Danube delta. The most prominent ridge in the Sărăturile ridge plain developed 350-250 years ago, suggesting increased marine and aeolian energy, contributing to a larger sediment supply into the foredune.