A paleoshoreline is a relict coastal depositional and/or erosional landscape formed during Quaternary periods of sea-level stillstand. Marine terraces are relatively flat surfaces, frequently bounded by steeper paleocliffs landward and a gentle slope seaward, resulting from marine abrasion (wave-cut platforms) or accumulation of sedimentary deposits (marine-built terraces) or reef constructions.

If well preserved, a marine terrace presents typical geomorphic features; the most relevant and positioned inland is the inner edge which can be correlated with the palaeoshoreline at the peak of the corresponding eustatic transgression. In addition, tidal notches, the upper limit of bands of lithophaga boring, sea caves, or beach ridges may be used to identify palaeoshoreline locations. All these features’ reliability as precise references for sea-level position depends on several factors, such as the local tidal range and exposure to wave energy.

Raised marine terraces or paleoshorelines result from the interaction between eustasy, glacio-hydro-isostasy, and neotectonics; consisting of “PalaeoGPS” markers crucial to reconstruct the timing and amount of the eustatic sea-level fluctuations, which can be applied to quantify the relative vertical crustal deformation and tectonic evolution along coastal areas. Similarly, submerged marine terraces/paleoshorelines may indicate either slow uplift or subsidence processes.

If the uplift is larger than the sea level rise rate, individual marine terraces and/or paleoshorelines correspond to distinct interglacial stages and may be preserved in the landscape, being the ones at higher elevations older, and progressively eroded and less preserved. For slower uplift rates, prominent marine terraces may have a polycyclic origin, as the result of re-occupation due to sea level return at an older terrace level after emergence. This may lead to the formation of younger marine terraces evidence, producing a reworking of older ones. However, the “re-occupation”-effect is still poorly understudied worldwide and, when not considered, promotes an erroneous age interpretation. This is very important for locations with changeable tectonic rates or under influence of glacio-hydro-isostasy, and when a flight terrace may not be dated by absolute geochronology methods with interpreted ages based only on the sea-level curve. Addressing these questions solves tectonic and paleoclimatic conundrums, contributing to the understanding of the long-term interaction of these processes.

The most common dating methods used are Radiocarbon, Luminescence, Electron Spin Resonance, U-series, Amino Acid Racemization, and cosmogenic Nuclides. However, obtaining absolute ages for Quaternary marine terraces or palaeoshoreline is still challenging because reliable datable terraced surfaces and deposits may be difficult to be sampled due to erosive processes and frequent re-occupation by aeolianites that cover and obscure previous marine and beach deposits.

Terraced deposits related to paleoshorelines, frequently referred to as shallow marine deposits, are a stratigraphic record of the paleoclimate and paleoenvironment evolution. Hence, working as a proxy archive of the marine conditions for their formation time.

This Research Topic welcomes research papers that investigate tectonic-sedimentary-palaeoclimatic interaction recorded by paleoshorelines/terraced deposits using multi-disciplinary approaches. We encourage original contributions from diverse fields of research and particularly welcome research papers using field-based multidisciplinary methodologies at different, possibly integrated, timescales.

Main topics:
• Coastal geomorphology (emerged and submerged) and sea-level changes;
• Rocky and sandy coasts as an archive of sea-level change;
• Coastal deposits and coral reefs as palaeoclimatic and natural hazards events archive;
• Coastal morphology and marine terrace deposits as evidence of interaction between isostasy, tectonics, and eustasy;
• And absolute dating methods applied to marine terraces and/or features indicative of paleo sea-level positioning.

Impact

Frontiers in Earth Science

Quaternary Science, Geomorphology and Paleoenvironment