Notches in the Northern Adriatic Sea: Genesis and development

Abstract

The genesis and development of the submerged notch occurring along the Northern Adriatic limestone coasts, surveyed at depth ranging between −0.35 and −2.8 m and amplitude consistent with the local tide is discussed using new and published data on its elevation and data on limestone lowering rates, collected using a micro-erosion meter and a traversing micro-erosion meter. Coastal limestone lowering rates in the Northern Adriatic range between 0.008 and 1.170 mm/y and they are about eight times higher than inland limestone lowering rates. Data support the hypothesis that notch is presently carving, even if no present-day notch has been surveyed in the area. The lack of a modern notch, and the presently submerged notch position, could be related to (1) a rapid still-acting tectonic downdrop or (2) an increase in weathering/erosion rates causing by different environmental conditions, e.g. during the so-called Medieval Warm Period, marked by more aggressive weathering, both chemically, biologically and/or mechanically, than present conditions, due to an increase in rainfall or variations in the acidity of seawater. Pros and cons of these hypotheses are discussed in the paper.