Differences in ¹⁴C Age Between Stratigraphically Associated Charcoal and Marine Shell from the Archaic Period Site of Kilometer 4, Southern Peru: Old Wood or Old Water?

Abstract

Consistently large differences occur in the calibrated 14C ages of stratigraphically associated shell and charcoal samples from Kilometer 4, an Archaic Period archaeological site located on the extreme south coast of Peru. A series of nine shell and charcoal samples were collected from a Late Archaic Period (~6000–4000 BP) sector of the site. After calibration, the intercepts of the charcoal dates were ~100–750 years older than the paired shell samples. Due to the hyper-arid conditions in this region that promote long-term preservation of organic material, we argue that the older charcoal dates are best explained by people using old wood for fuel during the Middle Holocene. Given this “old wood” problem, marine shell may actually be preferable to wood charcoal for dating archaeological sites in coastal desert environments as in southern Peru and Northern Chile.

Is it agriculture yet? Intensified maize-use at 1000 cal BC in the Soconusco and Mesoamerica

“…This is due in part to the movement of charcoal through sedimentary sequences, displacement of charcoal by burrowing animals, and root burns beneath the ground surface that contaminate older materials that are otherwise ordered stratigraphically. Identified maize kernels were preferentially targeted to confirm the associations between temporally diagnostic ceramic assemblages and the carbonized maize remains, but also to avoid the old wood problem (e.g., Schiffer, 1986;Kennett et al, 2002). Carbonized maize remains and other ecofacts (e.g., purified animal bone collagen; Kennett et al, 2008) are short-lived organisms and have a greater probability of accurately dating the depositional events of interest and, in this case, changes in the density of maize remains through time.…”

Intrashell Radiocarbon Variability in Marine Mollusks

“…Exploring the nature of early aquatic adaptations depends upon establishing viable chronologies, and marine mollusk shells are among the most ubiquitous and durable archaeological remains recovered from coastal sites around the world. In some coastal settings, the prehistoric use of old driftwood for fuel precludes its use in dating, leaving marine shells as the preferred material for chronology building (Erlandson et al 1996;Kennett et al 2002). Beyond establishing chronologies of subsistence and settlement via AMS 14 C dating, the appearance of possible shell ornaments in the Middle Paleolithic of North Africa and the Levant suggests that with improvements in the precision and accuracy of the AMS technique, archaeologists may document the emergence of the cognitive ability and symbolic behavior that is the hallmark of our species today (Vanhaeren et al 2006).…”

Trace metal storage in recent floodplain sediments along the Dill River, central Germany

“…and charcoal can be eroded from older sediments, thereby yielding an anomalously old age for sedimentation (Kennett et al, 2002;Seidel and Mäckel, 2007;Hoffmann et al, 2008). To avoid dating reworked charcoal, I used only charcoal fragments that appeared in large concentrations rather than as isolated fragments, given that the latter have a higher potential for being reworked from older deposits (DeLong and Arnold, 2007).…”