Geochronology and palaeoclimatic context of submerged siliciclastic beachrock formation in the western Mediterranean Sea

Carles Roqué Pau,Rogelio Linares Santiago,Mario Zarroca Hernández

doi:10.3989/scimar.05110.020

Carles Roqué Pau, Rogelio Linares Santiago + Show 1 more

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https://doi.org/10.3989/scimar.05110.020

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Abstract

This article describes the geomorphological and petrological characteristics of 19 submerged beachrocks located on the north Catalan coast (western Mediterranean Sea). Their length ranges between 8 and 1039 m, their width between 1.5 and 86.5 m and their thickness between 0.4 and 3.25 m. They are siliciclastic beachrocks consisting of well-rounded gravels with a very coarse sand matrix, and they have a low proportion of bioclasts (<1%). Cementation occurred in the swash zone and adjacent foreshore due to the precipitation of high magnesium calcite. From absolute dates (14C and optically stimulated luminescence) and anthropic artifacts, three phases of formation attributable to the Late Holocene were identified. Phase I corresponds to the warm and humid Roman Period and was recorded at a level below -3.75 m mean sea level (MSL). Phase II corresponds to the warm and arid Medieval Climate Anomaly and was recorded at +0.25 m to -2.5 m MSL. Phase III corresponds to the Little Ice Age and Industrial Period and was recorded at levels ranging from +0.5 m to -3.0 m MSL. Good temporal correspondence between the chronology of the cementation phases and warm and/or dry palaeoclimatic conditions can be established.

Highlights

IntroductionBeachrocks are consolidated coastal deposits formed by the lithification of beach sediments due to the precipitation of calcium carbonate (mostly high magnesium calcite and/or aragonite, and low magnesium calcite) (e.g. Scoffin and Stoddart 1987, Psomiadis et al 2009)
Beachrocks are consolidated coastal deposits formed by the lithification of beach sediments due to the precipitation of calcium carbonate (e.g. Scoffin and Stoddart 1987, Psomiadis et al 2009)
Up to 19 beachrocks were documented along the 215 km of the studied coastline, all of them submerged (Fig. 1)

Summary

Introduction

Beachrocks are consolidated coastal deposits formed by the lithification of beach sediments due to the precipitation of calcium carbonate (mostly high magnesium calcite and/or aragonite, and low magnesium calcite) (e.g. Scoffin and Stoddart 1987, Psomiadis et al 2009). Cementing occurs in the intertidal zone and under a thin layer of unconsolidated sediments (Webb et al 1999), cementing in the supratidal zone has been reported (Kelletat 2006). Beachrocks are formed both on beaches with a predominance of carbonaceous and siliciclastic particles and on beaches with silt to cobble-size sediments (Moissette et al 2013). Cementation is a very rapid process at a geological time scale, being of the order of months to years (Hopley 1986), so the granulometric and compositional characteristics of the beachrock reflect those of the beach from which they are formed (Psomiadis et al 2014). Recent studies show that carbonate precipitation induced by the activity of microorganisms plays an important role in the cementation of beachrocks (McCutcheon et al 2016, 2017, Ramachandran et al 2020, Daryono et al 2020)

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