Is it possible to identify temporal differences among combustion features in Middle Palaeolithic palimpsests? The archaeomagnetic evidence: A case study from level O at the Abric Romaní rock-shelter (Capellades, Spain)

Abstract Archaeomagnetic dating is probably one of the most known applications of magnetic methods to archaeology but there are others still underutilized and of particular interest to Palaeolithic archaeology. Here, we report a novel application of archaeomagnetism as a technique to determine temporal diachronies among combustion features from the same surface within palaeolithic palimpsests. The approach is based on the subtle directional changes of the Earth's magnetic field through time (secular variation, SV) and on the ability of burned materials to record such variations under certain conditions. Three Middle Palaeolithic hearths from level O (ca. 55 ka BP) at the Abric Romani rock-shelter (NE Spain), were archaeomagnetically investigated. The studied surface (black homogeneous carbonaceous facies), recorded the magnetic enhancement produced by fire with a tenfold increase in concentration-dependent magnetic parameters in the uppermost centimetre with respect to its unburned or deeper counterparts. Pseudo-single domain (PSD) Ti-low titanomagnetite was identified as the main remanence carrier. The irreversibility of thermomagnetic curves suggests that these samples did not undergo enough high temperatures as to record a full thermoremanence (TRM). Additionally, the occasional occurrence of maghaemitized magnetite is interpreted as an indication of a thermochemical remanent magnetization (TCRM), making these samples unsuitable for absolute palaeointensity determinations. Two well-defined (α95