SEDIMENTARY RADIOACTIVITY IN AN UPPER PALEOLITHIC-MIDDLE PALEOLITHIC (MP-UP) TRANSITION SITE: INCREASING ESR TOOTH DATING ACCURACY AT GOLEMA PEšT, NORTH MACEDONIA

Abstract

ESR (electron spin resonance) can date sites that span the whole Paleolithic, but requires accurate sedimentary dose rates, especially in caves where the internal and cosmic dose rates can approach 0 mGy/yr. This study examines the sedimentary radioactivity in the upper layers at Golema Pešt, North Macedonia. Reaching > 5.5 m deep, > 21 flatly lying, silty-sandy matrix-supported gravel layers with éboulis clasts fill the cave. In Sondage 2, Layers 0–5 contained many hearths and yielded thousands of bones and teeth, many from ungulates. In Layers 2-5a sat thousands of lithics and small tools, many made on tiny quartz crystals. Layers 2c-6 have Mousterian assemblages with denticulates, notched tools, Levallois cores and flakes. To measure the volumetrically averaged sedimentary dose rates for ungulate teeth dated by ESR from Sondage 2, 66 sediment samples were analyzed by NAA. Adding éboulis, calcined bone, and charcoal associated with the hearths lowered the sedimentary dose rates or left them unchanged. In Layer 2 at 198 cm below the cave datum, the Campanian Ignimbrite (CI) cryptotephra occurred, where it caused abnormally high sedimentary U, Th, and K concentrations and dose rates. Since the CI tephra lay 28–30 cm above AT77, a tooth dated from Layer 3, using time- and volumetrically averaging increased AT77’s sedimentary dose rate by 32%, and dropped its calculated age by 25%. Analyzing the sedimentary compositions at every 2 cm in Layers 0–2 yielded a highly detailed stratigraphy that reduced the uncertainty in the sedimentary dose rates and the ESR ages, but more detailed geochemical analyses must be completed within the lower layers in Sondage 2.

Sedimentary Dosimetry for the Saradj-Chuko Grotto: A Cave in a Lava Tube in the North-Central Caucasus, Russia

“…Not surprisingly, both [U inden ] and [U outden ] ranged from 136.12 to 162.38 ± 0.02 ppm, which produce D den (t) ranging from 3.751 ± 0.270 to 4.475 ± 0.322 mGy/y assuming an early U uptake model in the dentine. Again, [U den ] tend to range 100-150 ppm higher than comparable [U den ] values seen in dentine from karst caves [5,6,8,[25][26][27][28][29][30][31][32][33]38,39]. JT5 s D den (t) emits as much as~2.5-4.0 mGy/y, significantly more than in the comparable dentine seen in Middle Paleolithic teeth collected from karst caves.…”

“…To find the tooth's time and volumetrically averaged dose rate, D sed,γ (t) derived from the γ radiation sources can then be calculated by integrating all D sed,γ,i (t) over the 30 cm sphere and over time [6,8,15,16]. is This includes correcting D sed,γ,i (t) for any absorption or leaching of radioactive elements from the various sedimentary components [16].…”

“…Within Layer 6, [W sed (0)] ranged from 18.9 ± 0.3 to 23.8 ± 2.4 wt%, with higher uncertainties than seen in other layers. In most karst cave sediment, [W sed (0)] tends to average 5-15 wt% [5,6,8,[25][26][27][28][29][30][31][32][33]. At [W sed (0)] >12-15 wt%, the sediment feels damp, which tends to discourage both long-term human inhabitation and cave bear hibernation.…”

“…In karst caves, D sed,β (t) typically ranges from 100 to 500 µGy/y, while D sed,γ (t) varies from 300 to 1000 µGy/y, partly due to the limestone and éboulis that tend to range at 30-60 µGy/y for D sed,éb,β (t) and 100-250 µGy/y for D sed,éb, γ (t) [5,6,8,16,[25][26][27][28][29][30][31][32][33]. By comparison, at SCG, both D sed,β (t) and D sed,γ (t) range 3-15 times higher.…”

“…For most Middle Paleolithic teeth found in caves, however, low enamel and dentinal U concentrations often make D int (t) low, while D cos (t) tends to be small compared to D sed (t). Together, these factors result in dating limits that range from~10-20 ka to~3-4 Ma and ESR ages whose accuracy and precision depend critically depend upon the accuracy and precision in the D sed (t) measurements (see references in [1- 6,8]).…”