Transgressive Architecture of Coastal Barrier Systems in the Ofanto Incised Valley and Its Surrounding Shelf in Response to Stepped Sea-Level Rise

Vincenzo De Santis,Massimo Caldara,Luigi Pennetta

doi:10.3390/geosciences10120497

Vincenzo De Santis, Massimo Caldara + Show 1 more

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https://doi.org/10.3390/geosciences10120497

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Abstract

Coastal deposits/barriers react to sea-level rise through rollover or overstepping. Preserved coastal deposits/barriers allow us to examine coastal responses to sea-level rise, an important aspect within the context of climate change. This study identifies the Ofanto incised valley and examines the possible factors that caused the considerable difference in shape between this valley and adjacent valleys: the Carapelle and Cervaro incised valley and Manfredonia incised valley. In addition, this study assesses the response of transgressive units to stepped sea-level rise with a focus on the evolution of palaeo-barriers/shorelines on the continental shelf and within the infill of Ofanto incised valley. We identified the traces of two slowstands in sea-level rise: the first, short-lived at a centennial scale, interrupted Meltwater Pulse 1A; the second is referable to part of Bølling-Allerød and Younger Dryas. During these two slowstands, two barrier-shoreface/estuarine-backbarrier systems formed. Meltwater Pulse 1A and Meltwater Pulse 1B led to overstepping and partial preservation of these systems in the form of aligned topographic highs. The second slowstand gave rise to continuous landward backstepping of the coastal barrier system; during the following Meltwater Pulse 1B (MWP-1B), landward rollover of the coeval barrier/backbarrier system occurred.

Highlights

Rollover and overstepping are the two main responses of coastal barriers to sea-level rise [1].Rollover is dominant and consists of a continuous landward migration of the barrier systems, with almost complete reworking of shoreface and barrier deposits [2]
Overstepping and partial preservation of coastal deposits/barriers has been typically attributed to rapid sea-level rise, such as that occurred during meltwater pulses [6], under favourable circumstances: these include early cementation [7] or gravel and boulder barrier formation [2]
The aim of this study is to provide an example of how coastal depositional environments migrate landward as a response to stepped rises in sea level

Summary

Introduction

Rollover and overstepping are the two main responses of coastal barriers to sea-level rise [1].Rollover is dominant and consists of a continuous landward migration of the barrier systems, with almost complete reworking of shoreface and barrier deposits [2]. Overstepping consists of in place drowning of coastal deposits/barriers [3]; they can be preserved as relict features on the seafloor. Overstepping and partial preservation of coastal deposits/barriers has been typically attributed to rapid sea-level rise, such as that occurred during meltwater pulses [6], under favourable circumstances: these include early cementation (beachrock and aeolianite formation) [7] or gravel and boulder barrier formation [2]. According to Pretorius et al [8], coastal deposits/barriers, coupled with incised valley deposits, provide useful information on the evolution of coastal systems during transgression and provide important evidence for the relative balance between postglacial rises in sea level and the available sediment [9,10]. As the incised valley fill is conditioned by the shape of valleys, it is important to investigate the factors that drive the valley geometry, the principals among which are the rate and magnitude of the base-level fall, shelf-break depth, tectonics, climate, and drainage-basin area [11]

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