Our strategy was chosen specifically to date sandy ridges of the delta lobe strandplains and barrier

Transcription

1 Giosan 1 Data Repository Item DR Supplementary Information Coring and sampling strategy Our strategy was chosen specifically to date sandy ridges of the delta lobe strandplains and barrier beach plains as well as the barriers of the Razelm-Sinoe lagoon. Specimens for radiocarbon and optical dating were collected below the dune cap sands within the beach-foreshore facies on a beach ridge or from fine sediments below the last overwash event at the back of the ridge (Fig. DR 1). Figure DR 1. Coring and sampling strategy for dating. Cores at locations AA and CC will first penetrate the wellsorted, non-fosiliferous foredune or dune cap sands (number 1 in legend) respectively, to reach the underlying shellbearing beach/foreshore sands (number 2 in legend), whereas at location BB, the beach/foreshore sands will be at the surface. The upper limit of the beach/foreshore is a sea level indicator and is shown by the thick dashed line. At location DD, coring penetrates a succession of lacustrine/marsh/marine muddy deposits (number 3 in legend) interstratified with sandy overwash deposits. Intervals sampled for radiocarbon and optical dating are indicated by bold segments on the AA through DD lines. For radiocarbon dating, we assumed that articulated bivalves below the dune caps are contemporaneous with the ridge deposition because their articulation will not survive intense and/or repeated erosional-depositional cycles. This assumption is supported by the rare preservation of these specimens in both ancient and modern ridge deposits and is verified in several places by co-

2 Giosan 2 located optical dates. At the ridge backshore sites, the last overwash event reflects the stabilization age of a ridge, once it was isolated by other ridges prograding in front of it (Fig. DR1). The overwash event as well as both its lower and the upper bounds could provide the age for that event, which can be considered instantaneous at the time scales discussed here. We chose the interface between the well-sorted, non-fossiliferous (fore)dune cap sands and the underlying shell-bearing beach/foreshore sands as our sea level indicator (see e.g., Thompson, 1992; van Heteren et al., 2000; Rodriguez and Meyer, 2006 for a similar rationale). Sea level index points were obtained only for ridges that have been dated optically or using articulated mollusks. The uniform morphology and height of all the beach ridge and barrier plains in the Danube delta (CSADGGA, 1965) suggests that the wave regime responsible for the ridge development in the Danube delta has not differed significantly from the present one. Repeated field surveys on modern beach ridges of the Danube delta coast by us and others (RCMGG, 1994) show that the relief of the beach on which (fore)dunes are constructed does not exceed 1 m above sea level. Therefore, to obtain a sea level index point at each location, we subtracted 50 cm from the elevation of the interface between dune sands and beach/foreshore sands to which we attached a vertical error value (see below). For the cases where an overwash deposit date was used in the sea level model, the top of the beach/foreshore deposits were measured in nearby trenches on the dated ridge itself. The altitude error for our sea level index points is the cumulated error for measuring the sample depth (± 5 cm), for non-vertical coring (-3 cm per m), for the vertical indicative range for the beach/foreshore top (± 50 cm), and for leveling error of ± 50 cm (based on 1:25000; CSADGGA (1965) maps accuracy and a comparison to a delta region digital terrain model courtesy of I. Grigoras at the Danube Delta Institute). The stratigraphy of cores/augers is presented in Figure DR3. Compaction data are not available for the Danube delta, but it is expected to be minimal, given the predominantly sandy fill of the Danube incised valley system (****). Differential compaction is also expected to be minimal because coeval delta lobes and barrier systems (i.e., Sf.

3 Giosan 3 Gheorghe I and Zmeica; Sulina and Lupilor; Sf. Gheorghe II and Chituc) remained subaerial since the time they were built although muds are much more common as a fill of the incised valley in the Razelm-Sinoe lagoon than in the delta area (****). Figure DR2: Core/auger/trench locations for this study. Refer to. Fig. DR3 for zones A through C.

4 Giosan 4 Figure DR3: Generalized chronostratigraphy of studied cores/augers/trenches. A: from the open coast delta lobes; B. from the Dunavatz lobe; C. from the Razelm-Sinoe ridges. Circled numbers are identification numbers for locations (see Table DR1 and Fig. DR2). Altitude at each location is noted as are the radiocarbon ages (in bold dates used for the sea-level model; in italics other dates), optical ages (in boxes), and the in core location of samples on which they were measured. Legend: 1. peaty soil/soil with modern roots; 2. dune non-fosiliferous sands; 3. nearshore/beach/overwash sands (occasionally include cm-scale detrital organic-rich layers and/or muds); 4. muds.

5 Supplementary Table 1. Radiocarbon dates (a) b.r.p. beach ridge plain; b. p. barrier plain; l.s. lagoon system; (b) s. - single valve shell; a. articulated shell; m. multiple shells; f. fragment; p. peat; w.p. well-preserved). Calibrated ages in bold have been used for the delta chonology and the ones underlined for the sea-level model. No. Location(a) Lat Long Depth in Altitude Lab No. Material Condition(b) 14C age Calibrated age (2 sigma) core (m) (m) ST. GEORGE I LOBE 1 Caraorman b.r.p OS Cardium sp. s.; w.p ± 35 [6829 BP:7188 BP] 1 2 Caraorman b.r.p OS Abra sp. a ± 30 [3195 BP:3534 BP] 1 ZMEICA BARRIER 3 Razelm-Sinoe l.s OS Cardium sp. a ± 35 [4516 BP:4883 BP] 1 SULINA LOBE 4 Letea b.r.p OS Venus sp. s.; w.p ± 30 [2806 BP:3191 BP] 1 5 Letea b.r.p OS Cardium sp. s ± 60 [6751 BP:7175 BP] 1 6 Letea b.r.p OS Cardium sp. s ± 30 [5028 BP:5433 BP] 1 7 Letea b.r.p OS Abra sp. s.; w.p ± 40 [872 BP:1194 BP] downdrift b.p OS Abra sp. a ± 30 [2697 BP:2990 BP] 1 9 downdrift b.p OS Abra sp. a ± 30 [2309 BP:2671 BP] 1 10 downdrift b.p OS Abra sp. m ± 40 [1927 BP:2296 BP] 1 LUPILOR BARRIER 11 Razelm-Sinoe l.s OS Abra sp. a ± 40 [3096 BP:3467 BP] 1 12 Razelm-Sinoe l.s OS Abra sp. a ± 25 [3122 BP:3453 BP] 1 ISTRIA STRANDPLAIN I (OLDEST SET) 13 Razelm-Sinoe l.s OS Cerithium sp. w.p ± 40 [3346 BP:3692 BP] 1 Giosan 5 ST. GEORGE II LOBE 14 Saraturile b.r.p OS Abra sp. a ± 45 [1833 BP:2241 BP] 1 15 Saraturile b.r.p OS Abra sp. s ± 50 [1398 BP:1789 BP] 1 16 Saraturile b.r.p OS Abra sp. s.; w.p ± 50 [1800 BP:2216 BP] downdrift b.p OS Abra sp. a ± 35 [1688 BP:2040 BP] 1 18 downdrift b.p OS Abra sp. a ± 45 [1079 BP:1403 BP] 1 19 downdrift b.p OS Cardium? f ± 45 [2168 BP:2614 BP] 0.98; [2625 BP:2649 BP] downdrift b.p OS Abra sp. a ± 35 [478 BP:672 BP] 1 ISTRIA STRANDPLAIN II (YOUNGEST SET) 21 Razelm-Sinoe l.s OS Abra sp. a ± 40 [1172 BP:1483 BP] 1 22 Razelm-Sinoe l.s OS Abra sp. a ± 34 [681 BP:955 BP] 1 CHITUC STRANDPLAIN 23 Razelm-Sinoe l.s OS Abra sp. s. 475 ± 35 RANGE INVALID FOR CALIBRATION 24 Razelm-Sinoe l.s OS Abra sp. s ± 35 [2916 BP:3311 BP] 1 25 Razelm-Sinoe l.s OS Abra sp. s ± 45 [2703 BP:3043 BP] 1 26 Razelm-Sinoe l.s OS Cardium sp. s ± 45 [6315 BP:6667 BP] 1 DUNAVATZ LOBE 27 Razelm-Sinoe l.s ? OS peat in situ 310 ± 30 [301 BP:342 BP] 0.24 [346 BP:463 BP] Razelm-Sinoe l.s ? OS peat in situ 1880 ± 80 [1614 BP:1994 BP] 1 29 Razelm-Sinoe l.s ? OS peat in situ 265 ± 25 [153 BP:168 BP] 0.07; [283 BP:324 BP] 0.63; [376 BP:428 BP] 0.29; 30 Razelm-Sinoe l.s ? OS peat in situ 1540 ± 110 [1278 BP:1697 BP] 1 31 Razelm-Sinoe l.s ? OS Mytillus sp. s.; w.p ± 20 [5050 BP:5438 BP] 1 BISERICUTA and LEAHOVA BARRIERS 32 Razelm-Sinoe l.s OS Abra sp. a. 400 ± 35 RANGE INVALID FOR CALIBRATION 33 Razelm-Sinoe l.s OS Modiolus sp. s.; f ± 35 [736 BP:1049 BP] 1 34 Razelm-Sinoe l.s OS Cardium sp. a. 460 ± 40 RANGE INVALID FOR CALIBRATION

6 Giosan 6 Dating Well-preserved bivalves were the primary material for AMS radiocarbon dating at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) at the Woods Hole Oceanographic Institution. The methodology for AMS radiocarbon dating is presented on the NOSAMS site and discussed in e.g., McNichol et al. (1995). All radiocarbon dates, together with the depth in core for the dated samples and location of the cores are presented in Table DR1. Fourteen out of 30 dated bivalves were articulated. Several in situ peats were dated from cores penetrating the levee deposits of the Dunavatz distributary. However, exploratory dating of organic-rich layers within the beach ridge sands has proven unsuccessful, producing inconsistent ages downcore and demonstrating that these layers are detrital. Dates on single valve specimens in our entire dataset are generally older and discordant with dates on articulated shells, and we consider them reworked. Because articulated bivalves were not recovered on the wave-built updrift beach-ridge plain of the Sulina lobe (Letea) or the oldest Istria ridge, we used dates on non-articulated shells for chronology (Fig. 2 in the paper; Table DR1) to give a lower age limit for the start of progradation. On the outer Letea beach ridge set of the Sulina lobe, a single-valve of Abra sp. shell was dated, whereas for the oldest possible age for the inception of the Istria strandplain, we dated a Cerithium sp. gastropode shell. Optical dating on Danube delta samples was performed in Geoff Duller s lab at the University of Wales, Aberystwyth. Optical dating techniques used have recently been reviewed by Duller (2004). The samples for optical dating were collected below the water table in light proof tubes and transported to the laboratory ensuring that the sediment was not exposed to daylight. All the analysis in the laboratory was undertaken under subdued red lighting conditions that do not affect the luminescence signal, and preparation of the sample prior to luminescence measurements followed the general description given by Wintle (1997). Any organic

7 Giosan 7 material was removed using 10 volumes H 2 O 2 and any carbonates using 10% HCl. After drying, mineral grains between µm in diameter were selected using dry sieving. Quartz grains were separated using solutions of sodium polytungstate with densities of 2.62 and 2.70 g/cm 3 to remove feldspars and heavy minerals. Quartz grains were then placed in 40% hydrofluoric acid for 45 minutes in order to preferentially dissolve any remaining feldspars, and to etch away the outer skin of the quartz grains. The single aliquot regenerative dose (SAR) protocol reviewed in Duller (2004) was used to estimate the radiation dose that the samples had absorbed during burial. This protocol makes repeated OSL measurements of each sub-sample, or aliquot, so that the growth of the luminescence signal as a function of laboratory radiation dose can be determined (Figure DR4). SAR explicitly assesses the extent to which the sensitivity of each sample changes during this sequence of measurements, and compensates for this change. The equivalent dose (De) is calculated for each aliquot, and at least 20 aliquots were measured for each sample (Figure DR5). Within the SAR sequence, all OSL measurements were made while holding the sample at 125 C. The natural and regeneration signals were measured following a preheat step of 220 C for 10 seconds, and the test dose following heating to 160 C. To test the appropriateness of this SAR protocol to these samples, between 2 and 6 aliquots of each sample were bleached in the laboratory (using two sets of 100 s exposure to blue diodes) and then given a known laboratory radiation dose. These aliquots were then analyzed using the SAR protocol described above, and the apparent De calculated (Table DR2). The ratio of the given laboratory dose to that which was measured varied from 0.96 to 1.03, demonstrating that SAR is appropriate for these samples. Table 3 summarizes the results for the SAR measurements to determine the equivalent dose (De) for each sample. Twenty aliquots or more were measured for each sample, and the value given is the weighted mean. The dose rate in Table 3 is the sum of the beta, gamma and

8 Giosan 8 cosmic dose rates, adjusted where appropriate for water content and grain size. The final ages in Table 4 are calculated according to equation Luminescence (L x /T x ) Dose (Gy) Figure DR4: SAR growth curve for one aliquot of sample Aber85/LC4. The aliquot has a De of 4.2 Gy. Relative Probability Equivalent Dose (Gy) Figure DR5 Replicate measurements of equivalent dose (De) for sample Aber85/LC4. The solid line is a probability density function constructed from the 22 results. The individual De values and their errors are shown in ranked order. The final value of De used for age calculation is the weighted mean of these values (4.36 Gy).

9 Giosan 9 Table DR2: Results of the dose recovery experiment for each sample Given dose (Gy) Recovered dose (Gy) Ratio Given/Recovered LC LC LC LC LC5a Table DR3: Dosimetry data derived from thick source alpha counting and beta counting, and calculation of the cosmic dose rate. Sample Th (ppm) U (ppm) Beta dose (Gy/ka) Calculated K (%) Burial depth (m) Cosmic (Gy/ka) LC1 3.55± ± ± ± ± ±0.01 LC2 3.14± ± ± ± ± ±0.01 LC3 3.06± ± ± ± ± ±0.01 LC4 1.95± ± ± ± ± ±0.01 LC5a 0.55± ± ± ± ± ±0.01 Table DR4: Age data for samples from the Danube D e (Gy) Number of aliquots Preheat Water Con- Dose Rate Age (ka) ( C) tent (%) (Gy/ka) LC1 1.66± ±5 1.26± ±0.06 LC2 3.50± ±5 1.36± ±0.13 LC3 3.70± ±5 1.39± ±0.14 LC4 4.36± ±5 1.20± ±0.14 LC5a 2.84± ±5 0.55± ±0.28 Note: Water content is expressed as the weight of water divided by the weight of dry sediment.

10 Giosan 10 Chronological Model Unless otherwise identified, all dates discussed in this paper, including the ones published previously by other authors, have been converted to calendar ages in the same manner, using Calib software (Stuiver and Reimer, 1993; Hughen et al., 2004). We assumed a modern value for the reservoir age is 440 ± 40 yr BP with ΔR 75 ± 60 yr (Siani et al., 2001). For the in situ peat samples of the Dunavatz lobe, we used the terrestrial IntCal04 calibration dataset (Reimer et al., 2004). In the case of mollusk radiocarbon dates reported in Chepalyga (1984), we made no correction for the marine reservoir, which has been assumed to be of a similar value, but opposite sign, to the δ13c correction for isotope fractionation in the Black Sea, for which the published dates were not corrected (Kh. A. Arslanov, Radiocarbon Laboratory, Geographical Research Institute, St. Petersburg State University, personal communication). All dates are presented with a 2σ age error. Where available, we used luminescence dates instead of calibrated radiocarbon dates for the delta chronological model, except for a discounted optical date on the first beach ridge of 1330 ± 187 yr BP of the St. George II, which was measured on well-sorted, non-fossiliferous interpreted as a dune cap. Dates used in the chronological model for delta development and sea level reconstruction are identified in Table DR1. We synchronized the radiocarbon dates to the luminescence dates by adding 55 years to the calibrated 14 C dates. References Adamiec, G. and Aitken, M.J., 1998, Dose-rate conversion factors: update: Ancient TL, 16, p Chepalyga, A.L., Inland sea basins,: in Velichko, A.A., ed., Late Quaternary Environments of the Soviet Union: Minneapolis, University of Minnesota Press, p CSADGGA (Comitetul de Stat al Apelor Directia Generala de Gospodarire a Apelor), 1965, Harta topo-hidrografica, Dobrogea, scale 1:

11 Giosan 11 Duller, G.A.T., 2004, Luminescence dating of Quaternary sediments: recent developments: Journal of Quaternary Science, 19, p Hughen, K.A., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Bertrand, C.J.H., Blackwell, P.G., Buck, C.E., Burr, G.S., Cutler, K.B., Damon, P.E., Edwards, R.L., Fairbanks, R.G., Friedrich, M., Guilderson, T.P., Kromer, B., McCormac, F.G., Manning, S.W., Bronk Ramsey, C., Reimer, P.J., Reimer, R.W., Remmele, S., Southon, J.R., Stuiver, M., Talamo, S., Taylor, F.W., van der Plicht, J., Weyhenmeyer, C.E., 2004, Marine04- Marine radiocarbon age calibration, 26-0 ka BP: Radiocarbon, 46, p McNichol, A.P., Gagnon, A.R., Osborne, E.A., Hutton, D.L., von Reden, K.F. and Schneider, R.J., Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation. Radiocarbon, 37(3): RCMGG (Romanian Center for Marine Geology and Geoecology), 1994, Romanian Center for Marine Geology and Geoecology, Monitoringul ecologic al sistemului Dunare-Ddelta- Litoral- Mmarea Nneagra, Centrul Roman de Geologie si Geoecologie Marina. Reimer, P.J., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Bertrand, C.J.H., Blackwell, P.G., Buck, C.E., Burr, G.S., Cutler, K.B., Damon, P.E., Edwards, R.L., Fairbanks, R.G., Friedrich, M., Guilderson, T.P., Hogg, A.G., Hughen, K.A., Kromer, B., McCormac, F.G., Manning, S.W., Ramsey, C.B., Reimer, R.W., Remmele, S., Southon, J.R., Stuiver, M., Talamo, S., Taylor, F.W., van der Plicht, J., and Weyhenmeyer, C.E. 2004a. IntCal04 - Terrestrial radiocarbon age calibration, 26-0 ka BP: Radiocarbon, 46, p Rodriguez, A.B. and Meyer, C.T., 2006, Sea-level variation during the Holocene deduced from the morphologic and stratigraphic evolution of Morgan Peninsula, Alabama, U.S.A.: Journal of Sedimentary Research, 76, DOI: /jsr Siani, G., Paterne, M., Arnold, M., Bard, E., Métivier B., Tisnerat N., Bassinot, F., 2000, Radiocarbon reservoir ages in the Mediterranean Sea and Black Sea: Radiocarbon, 42, p Stuiver, M., and Reimer, P. J., 1993, Extended 14C database and revised CALIB radiocarbon calibration program, Radiocarbon 35: Thompson, T.A., 1992, Beach ridge development and lake level variation in southern Lake Michigan: Sedimentary Geology, 80, p Wintle, A.G., 1997, Luminescence dating: laboratory procedures and protocols, Radiation Measurements, 27, p

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