See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/269166124 Radiocarbon Dating, Mineralogy, and Isotopic Composition of Hackberry Endocarps from the Neolithic Site of Aşıkl... Article in Radiocarbon · December 2014 DOI: 10.2458/azu_rc.56.18322 CITATIONS READS 0 134 6 authors, including: Jay Quade Mary C. Stiner 278 PUBLICATIONS 13,554 CITATIONS 113 PUBLICATIONS 5,860 CITATIONS The University of Arizona SEE PROFILE The University of Arizona SEE PROFILE Susan M. Mentzer Mihriban Özbaşaran 26 PUBLICATIONS 196 CITATIONS 7 PUBLICATIONS 25 CITATIONS University of Tuebingen SEE PROFILE Istanbul University SEE PROFILE Some of the authors of this publication are also working on these related projects: Excavations at Bizmoune Cave View project Late Quaternary paleoclimate of the Thar Desert View project All content following this page was uploaded by Susan M. Mentzer on 06 December 2014. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. TREE-RING RESEARCH, Vol. 70(3), 2014, pp. S17–S25 DOI: http://dx.doi.org/10.3959/1536-1098-70.3.17 Copyright © 2014 by The Tree-Ring Society Radiocarbon, Vol 56, Nr 4, 2014, p S17–S25 DOI: http://dx.doi.org/10.2458/azu_rc.56.18322 © 2014 by the Arizona Board of Regents RADIOCARBON DATING, MINERALOGY, AND ISOTOPIC COMPOSITION OF HACKBERRY ENDOCARPS FROM THE NEOLITHIC SITE OF AŞIKLI HÖYÜK, CENTRAL TURKEY JAY QUADE1*, SHANYING LI2, MARY C. STINER3, AMY E. CLARK1,3, SUSAN M. MENTZER4, and MIHRIBAN ÖZBAŞARAN5 1 Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA. 2 Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA. 3 Department of Anthropology, University of Arizona, Tucson, AZ 85721, USA. 4 Institute for Archaeological Sciences, Eberhard Karls University Tübingen, 72070 Tübingen, Germany. 5 Department of Prehistory, Istanbul University, Istanbul, Turkey. *Corresponding author: quadej@email.arizona.edu. ABSTRACT Carbonate is abundant in many Neolithic tells and is a potentially useful archive for dating and climate reconstruction. In this paper, we focus on the mineralogy, radiocarbon dating, and stable isotope systematics of carbonate in hackberry endocarps. Hackberry fruits and seeds are edible in fresh and stored forms, and they were consumed in large quantities in many Neolithic sites in the Near East, including the site of our study, Aşıklı Höyük in central Anatolia, an Aceramic Neolithic tell occupied from about 9.4 to >10.3 BP (7.4 to >8.3 BCE). Detailed 14C age control provided by archaeological charcoal permits a test of the idelity in 14C dating of hackberry endocarps. Modern endocarps and leaves yield fraction modern 14C values of 1.050–1.066, consistent with levels present in the atmosphere when sampled in 2009. On the other hand, archaeological endocarps yield consistently younger ages than associated charcoal by ca. 130 14C years (ca. 220 calendar years) for samples about 10,000 years old. We speculate this is caused by the slight addition of calcite or recrystallization to calcite in the endocarp, as detected by scanning electron microscopy. Subtle addition or replacement of calcite by primary aragonite is not widely recognized in the 14C community, even though similar effects are reported from other natural carbonates such as shell carbonate. This small (but consistent) level of contamination supports the usefulness of endocarps in dating where other materials like charcoal are lacking. Before dating, however, hackberries should be carefully screened for mineralogical preservation and context. We examined the carbon and oxygen isotopic systematics of the fossil endocarps to try to establish potential source areas for harvesting. Most of the hackberries are enriched in 18O compared to local water sources, indicating that they were drawing on highly evaporated soil water, rather than the local (perched and regional) water table sampled in our study. Isotopic evidence therefore suggests that most but not all of the hackberries were harvested from nearby mesas well above the local streams and seeps fed by the water table. Keywords: radiocarbon, geoarchaeology, micromorphology, stable isotopes, microcontextual approach. INTRODUCTION Hackberries in Turkey are the annual fruits of Celtis tournefortii and the mineralized endocarps of the fruits are mostly carbonate (CaCO3). Because of their mineral content, hackberry endocarps are preserved abundantly in the Neolithic archaeological sites of Anatolia and the Levant, including Çatalhöyük (Shillito et al. 2009). Prior work developing the potential of hackberries and other calcareous seed endocarps for paleoenvironmental reconstruction (e.g. Wang et al. 1997; Jahren et al. 2001; Pustovoytov et al. 2010) motivated us to examine the utility of hackberry endocarps for 14C dating and paleoenvironmental reconstruction at Aşıklı Höyük. At 4 hectares in total area, Asıklı Höyük is the earliest large village in central Anatolia (Esin et al. 1991, 1999). The site is a tell standing ca. 14 m above the nearby Melendiz Creek (Figure 1), a perennial system nourished by run-off and groundwater from the nearby high peaks (>3000 m) of Hasan Dağ and the Melendiz Mountains. In more than 15 years of excavations at Asıklı Höyük, archaeologists have uncovered four main occupation levels spanning over 10 m of anthropogenic deposits. The deepest portions of the site are exposed (Figure 2) in the “Deep Sounding” located on the northern edge of the mound. At the base of the mound, Level 4 is characterized archaeologically by round and semi-round mudbrick structures and open-air activity areas. The overlying Level 3 contains multiple construction phases and is notable for a shift in the shape of buildings from round to rectangular, as well as the development of a large, deep midden, which we sampled in this study. In addition to its architectural features, Asıklı Höyük is notable for faunal evidence for “protodomestication” of sheep and goats (Buitenhuis 1997; Stiner et al. 2014). Previous 14C dating of mainly Levels 2 and 3 at Asıklı Höyük yielded dates that span roughly 8300–7400 BCE (10,300–9400 BP). Özbaşaran and Buitenhius (2002) have designated this interval as ECA (Early Central Anatolian) Phase II, roughly coeval with the pre-Pottery Neolithic A in the Levant. This study expands on the dating of Level 3 using charcoal and hackberries. Center for Mediterranean Archaeology and the Environment (CMATE) Special Issue Joint publication of Radiocarbon and Tree-Ring Research QUADE, LI, STINER, CLARK, MENTZER, and ÖZBAŞARAN S18 E34°09’ E34°15’ E34°21’ N38°25’ Mamasun Baraji ¨ ˇ Gulagac N38°23’ Demirci Kizilkaya DG10-13 ¸ Asikli Hoyuk ¨ ¨ N38°21’ DG10-4 M ele nd DG10-45 Ankara C iz N Turkey ¸ Asikli Hoyuk ¨ ¨ re ek Selime Uzunkaya 0 3 6 km DG10-49a DG10-54a et al.Höyük along Melendiz Creek in Figure 1. Location of the NeolithicFigure site 1atQuade Asıklı central Anatolia. Filled circles with sample numbers indicate locations of selected water samples in the immediate vicinity of the site (Table 2). Open circles are modern villages in the area. bedded -7m bedded bedded Level 2 yellow massive dung layer? dung layer? ch:9970±190 ce:9790±100 Level 3 36 ch:9770±140 ce:9560±120 -8m yellow massive bedded ch:9840±280 ce:9620±70 white brick bedded debris pit endocarp -9m ch:9780±120 23ce:9540±10 bedded ch:9860±260 ce:9620±70 south wall -10m Level 3 covered with bags 5N brick riser bench Level 4 6N mesoscarp endosperm ch:10050±140 ce:9540±60 ch:9740±170 ce:9620±70 7N Modern hackberries are spherical, 5–10 mm in diameter, and consist of three layers: an inner endosperm made of partially mineralized organic spheres, the well-mineralized endocarp with a honeycomb structure of ibrous carbonate and scalloped surface, and an outer leshy mesocarp (Figure 3). All previous studies identify aragonite and minor silica as the only mineralizing phases (Cowan et al. 1997; Wang et al. 1997; Jahren et al. 2001) (but see Results section). modern hackberry ch:9650±90 ce:9540±60 solid white faint bricks Hackberry fruits and seeds were consumed in large quantities at Asıklı Höyük. Macroscale observations and micromorphological analyses of sediment blocks indicate that hackberry endocarps are most abundant in the middens and open-air activity areas of Levels 4 and 3. The hackberry endocarps are present both as lenses and as isolated inds within more generalized refuse layers, the focus of sampling for this study. They are also found within the sediment overlying loor layers inside residential structures, and within mortar samples from Level 4. 4N 3N debris 1mm -11m 2N 1N 0N ch= charcoal ce = celtis endocarps Figure 2 Quade et al. Figure 2. Stratigraphic locations of the paired samples from the “Deep Sounding”/ Trench 4GH used for comparison of ages from co-occurring charcoal (ch) and Celtis endocarps (ce). Dated samples in calendar years (Table 1) are in bold letters. Samples 56 and 57 (Table 1) were collected from the south wall (not shown here) of Trench 4GH. Our main focus in this paper is on dating by 14C and stable isotopic analysis of hackberry endocarps. Further information about the context of the archaeological hackberries is provided by micromorphology, supplemented with micro-Fourier transform infrared analyses (µ-FTIR). This “microcontextual” approach (sensu Matthews 2005; Goldberg and Berna 2010) pairs different types of high-resolution analyses in order to understand impacts of site formation processes and sedimentary microenvironment on the preservation and context of sampled archaeological materials. A similar approach has been applied successfully in a Near Eastern tell setting to provide context for 14C dating samples (Toffolo et al. 2012). Figure 3. Scanning electron microscope image of the three distinct layers of a modern hackberry seed: (1) inner fruit or endosperm composed of partially mineralized spherical organic bodies, (2) endocarp consisting principally of aragonite and calcite, and (3) outer fruit or mesocarp with a framework of organic matter and some calcite crystals. Modern hackberry shrubs are living throughout the area today, in two main settings. The irst is along Melendiz Creek and its small tributaries incised into the local volcanic bedrock. The second is where shrubs grow on the dry volcanic mesas overlooking the Melendiz Creek drainage network. We sampled both modern hackberries and local water sources in the area to provide a context for interpreting the stable isotope results from archaeological hackberries in refuse layers at the site. METHODS Both modern and archaeological fruits were imaged using Zeiss Supra 35 scanning electron microscopy (SEM) at Miami University (Ohio). The SEM imaging was performed on uncoated, freshly broken surfaces of fruits. The imaging was conducted at an accelerating voltage of 2 keV with 7.0–8.5 mm working distance. Hackberry Endocarps from Neolithic Aşıklı Höyük The mineralogy of modern and fossil endocarps was irst evaluated using X-ray diffraction spectrometry (XRD) also at Miami University (Ohio). Endocarps were cleaned with distilled water and dried in room temperature. Samples were gently powered by hand using a mortar and pestle. XRD data were collected on a Sintag powder diffractometer, using CuKα radiation with an acceleration voltage of 40 keV and a tube current of 35 mA. Carbonate mineralogy was determined from mineral X-ray peaks (Tucker 1995). Further mineralogical analysis by µ-FTIR analyses were conducted on hackberry endocarps visible in thin section using a FTIR microscope equipped with a germanium crystal attenuated total relectance objective (Agilent Technologies). Infrared absorbance spectra were collected at resolutions of 4 cm–1 and compared to spectra produced from calcite, aragonite, amorphous silica, and apatite references using the same techniques. S19 accelerator facility. 14C years were converted to calendar years using CALIB 6.01 (http://calib.qub.ac.uk/calib/), and resultant ages expressed as the median of the 2σ (95%) calibrated age range. RESULTS AND DISCUSSION FTIR and Micromorphologic Evidence Archaeological contexts at Aşıklı Höyük that contain hackberries include hearths, occupation debris within structures, middens or refuse, stabling layers, and construction materials. Our micromorphological and µ-FTIR analyses of sediment samples collected from these contexts indicate that hackberry endocarps were variably impacted by postdepositional chemical alteration (Figure 4). Endocarps located in discrete refuse layers Oriented blocks of sediment were collected from exposed excavation proiles, impregnated with a mixture of polyester resin and styrene catalyzed with MEKP, and processed into petrographic thin sections. The thin sections were studied at a variety of magniications (10–200×) using petrographic microscopes, and described using standard terminology (Stoops 2003). At each modern water sample site, 15 mm of uniltered water was sealed with Telon and electrician’s tape into a centrifuge tube and refrigerated in the laboratory. δ18O (SMOW) of water samples was measured using the CO2 equilibration method on an automated sample preparation device attached directly to a Finnigan Delta S mass spectrometer at the University of Arizona. The δD values of water were measured using an automated chromium reduction device (H-Device) attached to the same mass spectrometer. The values were corrected based on internal lab standards, which are calibrated to SMOW and SLAP. The analytical precision for δ18O and δD measurements is 0.08‰ and 0.6‰, respectively (1σ). Water isotopic results are reported using standard δ-per mil notation relative to SMOW. Carbonates analyzed for δ18O and δ13C values were heated at 250°C for 3 hours in vacuo before stable isotopic analysis using an automated sample preparation device (Kiel III) attached directly to a Finnigan MAT 252 mass spectrometer at the University of Arizona. Measured δ18O and δ13C values were corrected using internal laboratory standards calibrated to NBS-19. Precision of repeated standards is ±0.11‰ for δ18O and 0.07 for δ13C (1σ). Carbonate isotopic results are reported using standard δ-per mil notation relative to VPDB. Charcoal samples for 14C analysis were pretreated using the conventional acid-base-acid protocol. Hackberry endocarps were pretreated in 2% H2O2 to remove organic matter, soaked overnight in distilled water, and copiously (>5×) rinsed in more distilled water before drying in an oven at 50°C. Samples were converted to CO2, graphitized, and analyzed at the University of Arizona NSF Figure 4. Microcontextual analysis of archaeological Celtis samples: (A) A Celtis endocarp in thin section. PPL. (B) Same view as (A), XPL. The outer edge of the endocarp is scalloped in morphology. (C) A phosphatized endocarp in a layer of dung is identiied by its yellow to orange color in PPL (pictured here) and isotropy in XPL. Note that the morphologies of crystals within the endocarp are generally similar to those of the unaltered endocarp in (A) and (B). (D) A burned endocarp in a hearth exhibits similar interference colors in XPL as an unaltered endocarp, although the morphology of the crystals is lost. (E) µ-FTIR measurements on the endocarps pictured above (locations indicated by numbers). The unaltered endocarp (1) exhibits absorbance peaks at 1445, 852, 711, and 668 cm–1, consistent with aragonite. The phosphatized endocarp (2) exhibits absorbance peaks at 1412, 1007, 871, 598, and 555 cm–1, consistent with apatite mixed with minor amounts of calcite. The heated endocarp (3) exhibits absorbance peaks at 1392, 870, and 711 cm–1, consistent with calcite. A small shoulder at 668 cm–1 indicates that some aragonite is still present. S20 QUADE, LI, STINER, CLARK, MENTZER, and ÖZBAŞARAN within middens are typically well preserved, and have not been impacted by physical reworking. Likewise, endocarps present in construction materials, such as mortar, are also well preserved; however, the overall composition of mortar samples indicates that they were produced from recycled debris within the site. For these reasons, the samples in this study were preferentially selected from midden contexts. Hackberry endocarps present in the occupation debris within structures and inside hearths are likely associated with primary processing and consumption activities. However, these contexts are not always ideal for dating samples due to mineralogical changes. Endocarps present inside hearths are composed of calcite (Figure 4e), likely as a result of conversion to calcium oxide during heating, followed by recarbonation upon cooling. Similarly, endocarps located in stabling layers exhibit secondary phosphatization with, in some cases, 100% replacement of the original aragonite by apatite (Figures 4c, e). Endocarps located in Level 4 activity spaces are likewise variably impacted by secondary phosphatization and recrystallization and are frequently physically reworked by human foot trafic, as evidenced by fragmentation and rounding. Carbon-14 Dating of Endocarps To contexturalize our archaeological samples, we dated a modern endocarp and leaf from hackberry shrubs living on a terrace carved into local volcanic bedrock about 1 km from the archaeological site. The leaf and endocarp of the living plant yielded post-bomb ages, with fraction modern carbon (FMC) at 1.050 and 1.066 (Table 1). Hackberries fruit yearly, and our results are consistent with the projected atmospheric FMC of ~1.05 (Levin et al. 2004) for our sampling year of 2009. This is also consistent with the indings of Wang et al. (1997), who documented 14C equilibrium between endocarp carbonate and the atmospheric CO2 from numerous samples spanning AD 1889 to 1993. From Aşıklı tell itself, we carefully sampled eight pairs of closely associated hackberry endocarps and charcoal, mostly from Level 3 (Figure 2). The host context of all samples is entirely midden or refuse layers, in which the endocarps are generally well preserved. The samples returned calibrated ages in the 9.5 to 10 kyr BP range, consistent with the general age constraints for Level 3 from other samples. Dating of co-occurring charcoal and endocarps in the Aşıklı deposits yields 14C ages for the endocarps that are slightly but systematically younger by 130 ± 90 14C years Table 1. 14C dates from paired Celtis endocarps and charcoal from Aşıklı Höyük. Sample Lab code Fraction cal yr BP AH’09- AA-1 Sample type2 modern C 14C yr BP (2σ >95%) 56 87975 0.3407 8790 ± 20 9800 ± 100 fossil Celtis endocarp 57 87962 charcoal 0.3342 8830 ± 40 9930 ± 230 58 87980 0.3421 8770 ± 20 9790 ± 100 fossil Celtis endocarp 59 87957 charcoal 0.3337 8850 ± 30 9970 ± 190 60 87981 0.3509 8570 ± 40 9540 ± 60 fossil Celtis endocarp 61 87959 charcoal 0.3387 8720 ± 20 9650 ± 90 62 87982 0.3473 8640 ± 30 9560 ± 120 fossil Celtis endocarp 63 87958 charcoal 0.3372 8770 ± 30 9770 ± 140 64 87987 0.3464 8670 ± 30 9620 ± 70 fossil Celtis endocarp 65 87955 charcoal 0.3372 8770 ± 40 9840 ± 280 66 87983 0.3505 8560 ± 40 9540 ± 60 fossil Celtis endocarp 67 87961 charcoal 0.3308 8910 ± 40 10,050 ± 140 68 87985 0.3457 8690 ± 20 9620 ± 70 fossil Celtis endocarp 69 87979 charcoal 0.3373 8760 ± 40 9740 ± 170 70 87986 0.3499 8570 ± 20 9540 ± 10 fossil Celtis endocarp 71 87956 charcoal 0.3377 8760 ± 20 9780 ± 120 72 87976 0.3454 8690 ± 20 9620 ± 70 fossil Celtis endocarp 73 87960 charcoal 0.3365 8780 ± 40 9860 ± 260 87977 1.0504 post-bomb — modern (2009) Celtis leaf 87984 post-bomb — modern (2009) Celtis endocarp 1.0660 1. AA- refers to Arizona Accelerator Facility number. 2. Listed as statigraphically paired charcoal and endocarps. Stratigraphic level upper Level 4 refuse upper Level 4 refuse upper Level 3 refuse/dung upper Level 3 refuse/dung lower Level 2 refuse lower Level 2 refuse upper Level 3 refuse upper Level 3 refuse middle Level 3 refuse middle Level 3 refuse middle Level 3 refuse middle Level 3 refuse basal Level 3 refuse basal Level 3 refuse lower Level 3 refuse lower Level 3 refuse basal Level 3 refuse basal Level 3 refuse on ignimbrite next to Dig house on ignimbrite next to Dig house Hackberry Endocarps from Neolithic Aşıklı Höyük (220 ± 120 calendar years) than the closely paired charcoal (Table 1; Figure 5b). ‐6 (a) charcoal ‐6.5 inversions, suggesting that the refuse layers represent a mixture of primary and recycled refuse, perhaps from ongoing excavation by Aşıklıans during house and other construction. Causes of the 14C Deiciency in Endocarps cel4s endocarps ‐7 stra%graphic depth (m) S21 One explanation we considered for the offset in ages between charcoal and endocarps is that the wood burned at the site could have been harvested from the older parts of trees. This could explain some but not all of the data, because some of the charcoal is burnt twigs, not ringwood. This mix of twigs and ringwood should not produce the consistently young ages of the endocarps compared coexisting charcoal. Pending testing with a larger data set, we tentatively reject this explanation. ‐7.5 ‐8 ‐8.5 ‐9 ‐9.5 ‐10 9400 9600 9800 10000 Alternatively, the fossil endocarps have been altered mineralogically or by isotopic exchange, in the process adding a small amount of 14C to samples. We investigated this possibility by examining the mineralogy, petrography, and surface morphology of modern and fossil endocarps. In hand specimens and petrographically, there is little evidence of alteration. Fossil endocarps retain a characteristic scalloped outer surface, although somewhat chalkier in appearance than modern endocarps. In thin section, the archaeological endocarps retained their high-order interference colors in cross-polarized light, and dense 10–30 μm crystals of aragonite characteristic of modern endocarps. 10200 calendar yrs BP 10200 (b) (b) 10100 cal yr BP charcoal 10000 9900 9800 9700 9600 9500 9400 9400 9500 9600 9700 9800 9900 10000 10100 10200 cal yr BP cel,s endocarp Figure 5. Calendar ages (in yr BP) of charcoal versus that of stratigraphically associated hackberry endocarps refuse layers, shown (a) by stratigraphic level and (b) by charcoal versus hackberry dates. The archaeological samples come from inely bedded refuse layers, typically 1–2 cm in thickness. The Level 4 and 3 midden area contains hundreds to thousands of discrete lenses of dumped debris sourcing from a variety of contexts. Lenses of hackberry endocarps contain hundreds of individual berries and likely source from food preparation activities that occurred elsewhere in the site. Paired charcoal samples from layers located immediately above or below derive from hearth rake-out. In micromorphology samples, the high-porosity, random orientation of coarse inclusions and lat contacts between lenses of refuse indicate that they were not signiicantly disturbed by human foot trafic or bioturbation following deposition. Although evidence for postdepositional disturbance is not present, human decisions regarding waste disposal within the site, such as secondary deposition of old waste, may have resulted in superposition of older and younger materials within the midden. Our results show stratigraphic inversion of both the charcoal and hackberry dates (Figures 2, 5a). Unpublished dates from elsewhere in the site also can show such A closer study of the samples by SEM and XRD reveals subtle but clear evidence of addition calcite to samples. The archaeological samples (AH-62 and AH10-47) retained the characteristic endosperm and endocarp but had lost the outer leshy mesocarp layer. Examination by SEM revealed two major differences between modern and archaeological endocarps: (1) secondary calcite crystals ca. 4–6 mm across are clearly present in archaeological hackberry endocarps, which suggest localized neomorphism of aragonite to calcite (Figure 6); and (2) rounded calcite aggregates in “honey-comb” cells of archaeological hackberry endocarps are more solid and are well lithiied (Figure 6). By contrast, calcite aggregates in modern hackberry endocarp display empty holes (Figure 6). Inilling of the holes apparently occurs after burial, perhaps by dissolution of aragonite and precipitation of calcite inilling of holes in the primary aragonite. Furthermore, XRD and SEM analyses of the modern hackberry endocarp, obtained from a living shrub, demonstrate the unexpected presence of calcite. Previous studies of modern hackberry endocarps all state that the only carbonate phase present is aragonite. Our sampled modern endocarp contains euhedral to subhedral bladed calcite (Figure 6); XRD analysis further conirms the presence of both aragonite and calcite in the modern endocarp (Figure 7b), similar to XRD results from archaeological endocarps (Figure 7a). At this point, we do not know if the presence of some primary calcite in the modern endocarp is a peculiarity of Celtis tournefortii or alternatively is present but undetected in other species of Celtis. QUADE, LI, STINER, CLARK, MENTZER, and ÖZBAŞARAN S22 modern hackberry AH-62 10μ Nonetheless, other hackberry data sets do show some indication of anomalously young ages. Wang et al. (1997) found that in many cases 14C dates from 8–35 ka endocarps were younger than that of co-occurring organic matter. However, they attributed the offset to layer mixing or contamination of the organic matter, not to problems with the carbonate dates. Their hackberry endocarps appeared well preserved, and free of detectable (<1%) contaminating secondary calcite. Pustavoytov and Riehl (2006) also observed burnt seed ages greater than biogenic carbonate ages in two out of seven cases from Lithospermum, another plant that produces carbonate-bearing fruits. AH10-47 10μ 10μ calcite 1μ 1μ holes 2μ (a) calcite solid calcite ? 1μ 1μ 1μ 1μ Figure 6. This igure compares modern (left) with archaeological (AH-62, center; AH10-47, right) hackberry endocarps at various levels of magniication under SEM. Carbonate minerals in both modern hackberry and archaeological endocarps are characterized by having a “honey-comb” texture (Wang et al. 1997). Each cell in the honey-comb consists of rounded calcite aggregates and surrounding ibrous aragonite. Open holes present in the modern sample become inilled with solid calcite in the archaeological samples AH-62 and AH10-47. intensity (counts) 300 200 a. fossil endocarp 100 b. modern endocarp 0 (b) reference calcite reference aragonite 10 20 30 40 50 2 theta (degrees) Figure 7. X-ray diffraction results reveal that the presence of aragonite and calcite minerals in endocarp of (a) fossil (AH10-47) and (b) modern hackberries. Previous studies only identify aragonite in modern endocarps. XRD traces for pure aragonite and calcite are shown for reference below. Perspective from Other Studies The 130-14C-year offset has not been described explicitly in any previous literature, perhaps because the offset is small and just above typical analytical errors of 50–100 years, and because the opportunity for ine-scale parallel sampling of charcoal and hackberries presented by the Asıklı Höyük case study is very unusual. In other studies (e.g. Wang et al. 1997; Pustovoytov and Riehl 2006), the archaeological sampling was not done by the geochronologists themselves; thus, it is not clear exactly how close the sampling associations are stratigraphically. Figure 8. The effects on 14C ages of variable (shown by lines 0.1 to 2%) modern contamination, compared to (a) fossil (≥50 ka) shell reported on by Rech et al. (2011), and to (b) hackberry endocarps from Asıklı. Carbonate from both fossil shell and hackberries display subtle but measurable 0.1–2% contamination by modern carbon. Hackberry Endocarps from Neolithic Aşıklı Höyük An offset of 130 years in 10-ka samples is the equivalent of ~0.5% contamination by modern carbon (Figure 8b). This level should be much more visible in old samples, where the effects of contamination are magniied by diminishing radiogenic 14C content: 0.5% contamination of a ≥50 ka sample would produce an age of ca. 40 ka (Figure 8a). We are not aware of any dating of such old endocarps. However, other very old ine-grained carbonate, such as shell aragonite, has been dated and it appears to experience the same subtle but measurable contamination, especially visible in older samples. Fossil shells studied by Rech et al. (2011) of ininite 14C age (>50 ka) returned ages of 35–48 ka (Figure 8a), which is consistent with 0.05 to 1.7% modern contamination. This overlaps the range of contamination of 0.1 to 1.5% contamination modern carbon from endocarps at Asıklı (Figure 8b). As in our study, Rech et al. (2011) demonstrated through SEM analysis the same subtle introduction of secondary calcite, in the case of shell as calcite overcoats onto primary aragonite. Implications for Dating of Endocarps S23 Stable Isotopic Composition In the Asıklı Höyük area, δ18O values of local meteoric waters range from –7.7 to –10.6‰, and δD values from –64 to –74‰ (Figure 1; Table 2). The lowest values come from upland locations at elevations above 1500 m, or from lowland stream and tap water apparently fed by these upland sources. Local spring water dripping from the Kızılkaya ignimbrite locally returned the highest isotopic values of –7.7‰ and –64‰ (Table 2, DGT10-4). The hackberry endocarps yield unusually high δ18O (PDB) values, mostly >0‰ (Table 3; Figure 9). We can contextualize our oxygen isotopic results by comparing them to a comprehensive data set of modern hackberry endocarps from North America assembled by Jahren et al. (2001). The δ18O values of North American endocarps are strongly correlated with the δ18O value of local meteoric water, and follow the relationship (recast from Jahren et al. 2001): δ18O(PDB)endocarp = 0.67δ18O(SMOW)meteoric water + 7.42 (r = 0.88) [1] Our work also demonstrates that although offset, dates obtained on Celtis may be suficient for the needs of many archaeologists working on sites <10,000 years in age where other reliable sources of anthropogenic carbon are absent. Before dating, however, the context and state preservation of the endocarps should be evaluated. The minor contamination of aragonite by calcite was only detected in this study using XRD. FTIR analyses of hackberry endocarps from midden contexts indicate aragonitic compositions. Similarly, Shillito et al. (2009: Figure 7) analyzed samples from Çatalhöyük using FTIR and reported peak positions consistent only with aragonite. The results of our work suggest that although prescreening potential dating or isotopic samples using FTIR is appropriate for eliminating phosphatized or strongly recrystallized endocarps, a mineralogical analysis such as XRD should be conducted on each sample prior to further measurements. This translates into a roughly +38‰ enrichment in endocarp aragonite compared to local source water (i.e. soil water). In Figure 9, we calculated the δ18O value of endocarp aragonite predicted by Equation 1 using local Asıklı Höyük waters compared to actual δ18O values of modern and fossil endocarps. The underlying assumption here is that the δ18O values of local water have not changed appreciably over the last 10,000 years. We ind that the δ18O values of most fossil endocarps lie between the ield deined by predicted δ18O values and that of the modern shrubs (Figure 9). This suggests that most fossil plants harvested for their hackberries at Aşıklı are drawing on evaporated soil water, rather than the local (perched and regional) water table sampled in our study. These plants grow in the dry, bare soil areas resting on volcanic rocks topographically above the well-watered, incised watercourses. Table 2. Isotopic composition of water in the Aşıklı area. Sample no. DGT10-4 DGT10-13 DGT10-36a DGT10-38b DGT10-45 DGT10-50a DGT10-51e DGT10-49a DGT10-54a DGT10-59a δ18O (SMOW) –7.7 –9.8 –10.4 –10.5 –9.0 –10.4 –10.6 –7.9 –9.7 –10.4 δD (SMOW) –64 –72 –71 –71 –70 –75 –74 –63 –73 –74 *All waters collected in July of 2010 or 2012. °N 38.34108 38.33399 NA 38.16317 38.32559 38.28327 38.26004 38.40454 38.29139 NA °E 34.23806 34.23616 NA 34.18647 34.23826 34.36150 34.41347 34.29044 34.21300 NA Elevation (m asl) 1121 1131 1378 1799 1137 1440 1784 1174 1287 1527 Type spring creek local tap local tap local tap local tap local tap spring local tap local tap Area local seep in ignimbrite Melendiz River at Aşıklı Helvedere - public tap Hasan Daği suction pump public tap Melendiz River near Güzelyurt east of Güzelyurt spring in travertine quarry village of Usunkaya Gösterli QUADE, LI, STINER, CLARK, MENTZER, and ÖZBAŞARAN S24 Table 3. Stable carbon isotope results from hackberry endocarps at Asıklı Höyük. Sample no. δ13C (PDB) δ18O (PDB) Sample type AH-mod-2 –11.0 +13.9 Celtis endocarp (modern) AH mod-3 –11.0 +13.3 Celtis endocarp (modern) AH’09-56-1a –9.8 +5.5 Celtis endocarp (archaeological) AH’09-56-1b –9.5 +6.7 Celtis endocarp (archaeological) AH’09-56-1c –9.7 +6.3 Celtis endocarp (archaeological) AH’09-56-1d –9.6 +6.6 Celtis endocarp (archaeological) AH’09-56-1e –10.6 +3.6 Celtis endocarp (archaeological) AH’09-56-2 –10.0 +9.1 Celtis endocarp (archaeological) AH’09-56-3 –10.2 +7.9 Celtis endocarp (archaeological) AH’09-56-4 –9.5 +5.7 Celtis endocarp (archaeological) AH’09-56-5 –12.1 +7.1 Celtis endocarp (archaeological) AH’09-58-1a –9.7 +8.9 Celtis endocarp (archaeological) AH’09-58-1b –10.2 +9.2 Celtis endocarp (archaeological) AH’09-58-2 –8.2 +9.9 Celtis endocarp (archaeological) AH’09-58-3 –9.4 +13.9 Celtis endocarp (archaeological) AH’09-58-4 –8.7 +12.9 Celtis endocarp (archaeological) AH’09-58-5 –10.3 +10.0 Celtis endocarp (archaeological) AH’09-60-1a –8.5 +6.5 Celtis endocarp (archaeological) AH’09-60-1b –8.5 +6.3 Celtis endocarp (archaeological) AH’09-60-2 –10.7 +6.8 Celtis endocarp (archaeological) AH’09-60-3 –8.1 +5.1 Celtis endocarp (archaeological) AH’09-60-4 –10.7 +8.2 Celtis endocarp (archaeological) AH’09-60-5 –9.9 +9.2 Celtis endocarp (archaeological) AH’09-62-1a –6.5 +7.1 Celtis endocarp (archaeological) AH’09-62-1b –6.6 +6.9 Celtis endocarp (archaeological) AH’09-62-1c –6.5 +6.7 Celtis endocarp (archaeological) AH’09-62-1d –6.6 +5.5 Celtis endocarp (archaeological) AH’09-62-1e –6.6 +6.8 Celtis endocarp (archaeological) AH’09-62-2 –10.3 +9.3 Celtis endocarp (archaeological) AH’09-62-3 –9.5 +7.5 Celtis endocarp (archaeological) AH’09-62-4 –9.8 +6.8 Celtis endocarp (archaeological) AH’09-62-5 –9.2 +5.6 Celtis endocarp (archaeological) AH’09-64-1a –7.3 –4.1 Celtis endocarp (archaeological) AH’09-64-1b –7.9 –2.1 Celtis endocarp (archaeological) AH’09-64-1c –7.5 –4.0 Celtis endocarp (archaeological) AH’09-64-1d –7.3 –3.7 Celtis endocarp (archaeological) *Archaeological site located at 38.34974°N; 34.22954°E; 1108 m. See Table 1 for 14C dates from these samples and stratigraphic context. An interesting exception is represented by four endocarps, samples AH-64a-d in Table 3. These yielded signiicantly lower values than predicted from local meteoric water values (Figure 9), Figure 9. δ18O (PDB) versus δ13C (PDB) values of both modern and fossil hackberry endocarps. We compare these analyses to that of endocarps predicted to form from a range of local meteoric waters (horizontal lines) using the endocarp-water relationship for North American hackberries described in Jahren et al. (2001) (see text). and therefore must have been imported from outside the region (to the north and/or at a higher elevation). This analysis assumes, of course, that the isotopic relationships observed for modern endocarps and water in North America holds for Cappadocia. 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