Appendix: Dating Methods Applied to Azokh Cave Sites

Abstract Dating is basic for archaeological and paleontological investigations and results of different dating methods used in Azokh caves are described in this chapter. Fossils from Azokh were not dated by any method previously. Lithic technology and taxonomy suggested a middle Pleistocene age for Unit V (from where Acheulian industries and a human mandible fragment were recovered) while Units III and II yielded Mousterian industries indicating middle Paleolithic ages. Dates from Azokh by Electron Spin Resonance (ESR) previously published elsewhere were given before final calculations and they slightly differ from those given in this Appendix, which are the definitive dating results.

Y. Fernández-Jalvo (&)

Museo Nacional de Ciencias Naturales (CSIC), José Gutiérrez Abascal, 2, 28006Madrid ES, Spain

e-mail: yfj@mncn.csic.es

P. Ditchfield

Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford, OX1 3QY, UK

e-mail: peter.ditchfield@rlaha.ox.ac.uk

R. Grün W. Lees M. Aubert

Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia

e-mail: Rainer.Grun@anu.edu.au

T. Torres J.E. Ortiz A.D. Bautista

Biomolecular Stratigraphy Laboratory (BSL), E.T.S.I. Minas, Polytechnical University of Madrid, Rios Rosas 21,

28003 Madrid, Spain

e-mail: trinidad.torres@upm.es

J.E. Ortiz

e-mail: joseeugenio.ortiz@upm.es

A.D. Bautista

e-mail: arantxa.diaz@gcpv.com

R. Pickering

School of Earth Sciences, University of Melbourne, Parkville, Melbourne, VIC 3010, Australia

e-mail: r.pickering@unimelb.edu.au

Резюме Датировка является важнейшим этапом археологических и палеонтологических исследований, и в данном разделе описаны результаты различных техник датировки, использованных для Азохской пещеры. Находки из Азоха ранее не были датированы каким-либо методом. Технологияполучениякаменныхорудийитаксономияфауны указывают на среднеплейстоценовый возраст подразделения V (где были найдены ашельские орудия и фрагмент нижней челюсти человека), в то время как подразделения III и II с мустерианской индустрией имеют среднепалеолитический возраст. Датировки Азоха методом электронного спинового резонанса (ЭСР), ранее опубликованные в литературе, были полученыдопроведениязавершающихвычисленийипотому они немного отличаются от представленных в этом приложении, являющихся окончательными оценками. Результаты ЭСР и метода рацемизации указывают на возраст около 300 тыс. лет для находок из подразделения V, вто время как техника ЭСР для поверхностных горизонтов плейстоценовых седиментов в Азох 1 дает оценку около 100 тыс. лет.

Серия изотопов урана была использована для датировки спелеотема из маленьких цельных камер во фронтальной и самой нижней секциях Азох 1. Возраст спелеотема оказался в пределах 1,19 ± 0,08 млн. лет. Это является минимальной оценкой времени зарождения самой пещеры, подтверждая древность отложений и указывая на возможность существования более ранних слоев со следами заселения.

Датировка методом 14С была использована для наиболее молодых отложений. Современные останки, найденные в подразделении 2 пещеры Азох 2, имели надежную датировку между 670 и 805 гг. н.э. Радиоуглеродная датировка древесного угля, обнаруженного рядом с современным зубом в подразделении А пещеры Азох 5, старше и имеет возраст от 722 до 384 гг. до н.э., в то время как верхняя поверхность седиментов в Азох 5 имеет возраст между 126 и 178 гг. н.э.

Keywords Dating methods Radiocarbon Electron Spin Resonance (ESR) Racemization Uranium-Lead (U-Pb) dating

Introduction and Summary (Yolanda

Fernández-Jalvo)

Dating is basic for archaeological and paleontological investigations, and results of the different dating methods used in Azokh caves are especially relevant. Fossils from Azokh have not been previously chronometrically dated by any method. Lithic technology and taxonomy suggested a Middle Pleistocene age for Unit V (from where Acheulian industries and a human mandible fragment were recovered) while Units III and II yielded Mousterian industries, indicating Middle Paleolithic ages (Lioubine 2002). Dates from Azokh by Electron Spin Resonance (ESR), previously referred to by Fernández-Jalvo et al. (2010), were published before final calculations, and revised dates are given in this Appendix, in Table 16.1.

Previous archaeological work conducted before the 1980s in the cave removed most sediments from the Azokh 1 site. Excavations performed since 2002 have focused on the undisturbed sediments located at the back of the cave, about 40 m from the open air connection. Most sediment infill of

this cave system has been deposited from the interior towards the exterior (Murray et al. 2016). The location of the excavation area and the internal origin of sediments restrict the application of some methods based on cosmic radiation to obtain dates for fossils contained in these sediments. Two of these methods are optically stimulated luminescence (OSL) and thermoluminiscence (TL). These are dating methods determining the time elapsed since the crystalline mineral contents in sediments (e.g., quartz, feldspars) were last exposed to sunlight (‘zeroing’ event). In the case of TL, clock resetting also occurs when materials are exposed to heating (e.g., burnt flint, ceramics or lava). The age is determined by measuring the amount of radiation per unit time (dose) that the sample was exposed to sunlight (and/or fire in the case of TL). Samples from Azokh 1 could not be dated by OSL or TL due to the distance from the open air and lack of exposure to the sun or fire.

Radiocarbon

Radiocarbon dating has been applied to the youngest sediments recorded in the Azokh sites (see Sect. 16.2 below). This method is based on radioactive decay of the isotope 14C, which provides highly reliable dates (Weiner 2010). The use

of accelerator mass spectrometry (AMS) has greatly reduced the amount of sample needed, has increased the precision of radiocarbon dating and extended the limit of this method up to 60 ka. Dates obtained through radiocarbon methods are expressed as years 14C BP (uncalibrated radiocarbon years before present, considering ‘present’ as 1950). This is based on the assumption that the atmospheric carbon concentration has always been the same since 1950. Radiocarbon dates can be calibrated by dendrochronology, together with the Intcal 09 calibration data set (Reimer 2009). Plots obtained from calibration confirm the validity of the results obtained and provide an accurate crosscheck (Fig. 16.1). These plots show a double set of curves. The left hand axis (Y-axis) shows the

radiocarbon concentration curve with a precision of ±30 to 20 years error (see Table 16.1, 14C dating) expressed in years BP (before present). The bottom axis (X-axis) shows the calibration curves given as an age range of possible dates expressed in cal [k]BP, calAD or calBC (calibrated or calendar years). The results of calibration in these plots are expressed as a percentage of confidence.

The material to be dated by radiocarbon includes all organic matter, burnt or not, such as vegetal remains (charcoal or seeds) as well as fossil bone. However, the carbon-oxygen bond is relatively fragile, and re-crystallization and incorporation of exogenous ions into the mineral phase of the originally calcified tissues can occur during fossilization (Lee-Thorp 2002).

As a result, carbon-containing minerals are rarely dated (Weiner 2010), but carbon from collagen in bones is frequently dated by radiocarbon. In the case of Azokh 1, the bone materials did not contain enough carbon to be dated by radiocarbon, probably due to the action of bat guano (see Smith et al. 2016). Charcoal was the only possible material that did not fail from Azokh 1. However, results from Unit I are too young and those from Unit III are too old for radiocarbon dating (Table 16.1).

Valid results were obtained from Azokh 2 (Unit 2) that gave an age between 670 and 805 years calAD. This site is close to the cave entrance (Murray et al. 2016), so that bat guano has not affected the results. Both vegetal and bone material from Unit 1 are too young to date (as was the case with those of Unit I from Azokh 1).

The Azokh 5 site has provided good radiocarbon dating results both for bone and charcoal. AZK14 (OxA 17589) is a