Pecten as a new substrate for IcPD dating: The quaternary raised beaches in the Gulf of Corinth, Greece

Abstract

13Intra-crystalline protein diagenesis (IcPD), a recent development of amino acid racemization 14 dating (AAR), is now established as a reliable geochronological tool for the Quaternary. 15However, extending the method to new biominerals requires extensive testing in order to 16 provide evidence for the closed-system behaviour of the intra-crystalline proteins and to 17 assess the temporal span that can be covered. 18Here we present results from high-temperature experiments on the IcPD of the bivalve We conclude that Pecten is a potentially good substrate for IcPD dating in the Mediterranean, 27 and that the temporal limit of the technique in this area lies beyond MIS 11. 28 Highlights 29• A 48-h bleaching step isolates the intra-crystalline fraction of proteins from the 30 modern marine bivalve Pecten. 31• The intra-crystalline proteins behave as an effectively closed system during artificial 32 diagenesis. 33• The patterns of diagenesis are predictable, but may differ between high temperature 34 experiments and normal burial temperatures. 35• The extent of IcPD was determined for Pecten within a restricted geographical area 36 (the Gulf of Corinth, Greece). 37• There is a concordance between the extent of IcPD and correlated age estimates back 38 to MIS 11 in this region, although the resolution decreases beyond MIS 7.

The shell matrix of the european thorny oyster, Spondylus gaederopus: microstructural and molecular characterization

“…The finding that Spondylus matrices are rather organic-poor is consistent with the data obtained on other cross-lamellar (Agbaje et al, 2019;Demarchi et al, 2015;Marie et al, 2013a;Osuna-Mascaró et al, 2014) and foliated (Pierini et al, 2016) shells; this contrasts to what is observed in organic-rich nacreous and prismatic microstructures (Marie et al, 2009b;Marin et al, 2013;Sakalauskaite et al, 2019). As spondylids represent a bivalve family that emerged rather recently, in the Middle Jurassic (Waller, 2006), our observations corroborate the pioneering idea of Palmer that, in molluscs, the "cost" for making a shell is mostly driven by the "cost" to synthesize the organic matrix (Palmer, 1992); we can argue that evolution was directed to strike a balance between the mechanical properties of a biomineral and the actual "cost" required to produce it.…”

Protein sequences bound to mineral surfaces persist into deep time

“…All samples were analysed for chiral amino acids, and the concentrations were always well above the limit of detection ( Figure 4 ). Low concentrations in the oldest samples would have indicated that contamination is likely even in a theoretically closed system, but our values for Wonderwerk, Olduvai and Laetoli are ~150–200 times higher than the typical blank values calculated on a normal RP-HPLC analytical run in the NEaar laboratory (University of York) ( Demarchi et al., 2011 , 2015 ; Pierini et al., 2016 ). The concentration values are typically affected by a larger error than D/L values due to calculation errors introduced during sample preparation, explaining the variability observed.…”

Lithospheric flexure and rheology determined by climate cycle markers in the Corinth Rift

“…3b). This age designation is supported by U/Th coral datings 28–30 and IcPD dating of Pecten 31 . Although our shoreline angle elevations and terrace mapping are more accurate, this correlation is in essence similar to the interpretation of Armijo et al .…”