Transgressive rocky coasts in the geological record: Insights from Miocene granitic rocky shorelines and modern examples

Rocky shorelines are commonly punctuated, with alternating high relief cliffs and incised embayments which host pocket beaches. While multiple cases of ancient rocky shorelines associated with low relief ravinement surfaces have been documented in the geological record, deposits formed in pocket beaches and joint-cut coves are more rarely described. This poses the question are high relief rocky coastlines and their associated de-posits not preserved or have they been previously overlooked? Here we document exhumed examples of ancient granitic rocky shoreline systems of diverse morphologies from the Early Miocene of northern Austria, and com-pare them with modern systems in UK, Corsica, Spain and Norway. The preserved ancient examples offer a good opportunity to characterize these sedimentary systems, provide diagnostic criteria for their recognition and dis-cuss the main controls on their occurrence and preservation in the rock record. From their stratigraphic and sedimentological analysis, and its comparison with modern examples, we interpret that these rocky shorelines form and get preserved during rapid rates of combined tectonic and eustatic sea-level rise, along lithological, structural and weathered weakness zones affected by normal low wave energy condi-tions interrupted by storms. These results provide a mechanism for predicting their potential occurrence and dis-tribution during transgression of rocky coasts, with implications for exploration around structural highs and coastal management.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

We discovered diverse forms of ancient granite rocky shoreline systems from the Early Miocene in northern Austria, and compare them with modern systems in the UK, Corsica, Spain, and Norway. Through stratigraphic and sedimentological analysis, we concluded that these rocky shorelines formed and were preserved during rapid tectonic and eustatic sea-level rise, along lithological, structural, and weathered weakness zones affected by normal low wave energy conditions interrupted by storms. These results provide a mechanism for predicting their potential occurrence and distribution during transgression of rocky coasts, with implications for exploration around structural highs and coastal management.