Thermo-microstratigraphy of shells reveals invisible fire use and possible cooking in the archaeological record

The archaeological visibility of hearths related to shellfish cooking methods is limited, particularly in pre-ceramic shell midden contexts. Important evidence for use fire the thermal alteration components, namely identification burnt shells. Mollusk shells that mineralize as aragonite are indicative burning due conversion calcite through recrystallization at known temperature thresholds. However, roasting temperatures needed open bivalves, do not necessarily cause alterations cooked shell. This complicates significance mineralogy by itself recognize cooking, and discerning pre-depositional from situ heating. To distinguish between burning, we combine micromorphological analyses with microscopic Fourier transformed infrared spectroscopy investigate mineralogical thermo-alterations alongside microstratigraphic formation studies. Experimentally heated specimens Cerastoderma edule Scrobicularia plana used identify thresholds biogenic calcium carbonate phase micro-scale. These results then interpret mineral deposits two Mesolithic contexts Portugal. Micro-stratigraphically controlled proved be useful heating heating, configuring a novel methodology recognition traces versus other purposes. Mapping micro stratigraphic scale also allows us instances events were invisible macroscopically. combined considerably increases our capacity deciphering intricate stratigraphy occupational events.