Journal of Geophysical Research – Solid Earth Supporting Information for Penultimate Predecessors of the 2004 Indian Ocean tsunami in Sumatra: Stratigraphic, Archeological and Historical Evidence Kerry Sieh,1* Patrick Daly,1,2 E. Edwards McKinnon,3 Jessica E. Pilarczyk,1,4,5 Hong-Wei Chiang,1 Benjamin Horton,1,4,5 Charles M. Rubin,1 Chuan-Chou Shen,6 Nazli Ismail,7 Christopher H. Vane,8 and R. Michael Feener9 1 Earth Observatory of Singapore, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 2 University Scholars Programme, National University of Singapore, University Town, 18 College Avenue East, Singapore 138593 3 Institute of Southeast Asian Studies, Nalanda-Srivijaya Project, Archaeology Unit, Heng Mui Keng Terrace, Singapore 119614 4 Institute of Marine and Coastal Science, Rutgers University, New Brunswick, NJ 08901, USA 5 Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA 6 Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, Republic of China 7 Department of Physics/Geophysics, Faculty of Mathematic and Natural Sciences, Syiah Kuala University, Jalan Syech Abdurrauf, Darussalam - Banda Aceh 23111, Indonesia 8 British Geological Survey, Centre for Environmental Geochemistry, Keyworth, Nottingham, NG12 5GG, UK 9 Asia Research Institute, National University of Singapore, Singapore *Corresponding author: sieh@ntu.edu.sg Contents of this file Text S1 to S30 Figures S1.1 to S4.2 Tables S2.1 to S5.7 Additional Supporting Information (Files uploaded separately) Figure S1.6 1 Introduction We investigated two seacliff exposures (Lhok Cut and Lubhok Bay Beach) along the Lamreh Peninsula (Figure 1). At the Lhok Cut site, we found archeological deposits capped by a tsunami deposit that arrived from the sea. At the Lubhok Bay Beach site, we found two tsunami deposits within a small alluvial fan. This Supporting Information comprises observations and analyses that help substantiate our claims in the paper. 1. Images 1.1 Lhok Cut site Figure S1.1. Overhead view of the lime-plaster floor and one of the postholes that pierces it in the seacliff exposure. 2 Figure S1.2. Photographs of the mapped Lhok Cut seacliff exposure. The lower photo shows nearly the entire mapped exposure, for comparison with Figure 4 in the main text. The upper photo is a close up of the cobbly destruction layer that overlies the lime-plaster floor in the seacliff exposure. The large cobbles are Porites sp. coral. 3 A B Figure S1.3. Overhead views of the lime-plaster floor in the square and rectangular excavations into the earthen mound (Fig. 3). Note the window into the underlying stone foundation in the lower left of the square excavation. Small Porites sp. boulder resting on the lime-plaster floor in the middle of the lower photo may have been emplaced by a tsunami. Width of both excavations is about a meter. 4 Description of units exposed in excavation of the earthen mound EM 1: Uppermost (about 0.10 m thick) rich soil layer, high organic content and heavily bioturbated. Contains a mix of stone fragments, shells, a few residual ceramic sherds and modern debris. Contemporary ground surface is in an area of current human activity. EM 2: Underlying the modern ground surface (about 0.50 m thick) is a brown, friable sandy soil that has a poorly sorted matrix with fragments of charcoal, animal bone, earthenware and stoneware ceramics, and fragments of iron. Abundant stones (ranging up to 0.5 m in diameter) that are smooth and well-rounded. Although poorly articulated, it seems likely that the stones were part of a structure. It is clear from the composition of the matrix that this layer was a cultural construction. EM 3: Loosely compacted brown sandy soil (about 0.20 m thick) with coarse sand and about 20% small limestone fragments and occasional large rounded stones. Cultural material both includes both earthenware and stoneware ceramics, animal bone fragments, metal, and glass fragments. It is clear from the composition of the matrix that the layer was a cultural construction, although lacking any indication of structure. Midden material may be the fill for the structure. EM 4: Loosely compacted greyish-brown sandy soil (about 0.45m thick). The color of the soil lightens downward through the unit. Limited fragments of ceramics and larger stones (mostly concentrated in the southeast corner of the trench) and numerous shell fragments are present within the unit. The matrix is poorly sorted and contains ~20% small limestone flakes. EM 5: Highly compacted very fine white lime-plaster deposit with less than 15% small limestone fragments. No cultural material was found in the unit. We interpret this unit as a deliberate and constructed deposit, likely serving as a floor or foundation for a structure. No evidence for post-holes in the area exposed. EM 6: Layer of limestone and coral blocks packed with coarse lime powder directly underlying the lime-plaster deposit. No cultural inclusions are present. The excavation stopped at this layer, but this may well not be the bottom of the sequence. See Figure S1.4 for photograph of pristine coral cobble from this unit, which was used to date construction precisely (see Supporting Information, Section 5). 5 Figure S1.4. Uneroded and unweathered large cobble of coral within the openframework stony foundation of the lime-plaster floor beneath the earthen mound. Since the cobble was plucked alive from the sea just before incorporation into the foundation, the AD 1366±3.3 U-Th age of the coral dates precisely the construction of the structure. The long-axis of the cobble is about 20 cm. 1.2 Lubhok Bay Beach site Figure S1.5. Photograph of a WWII Japanese bunker about 40 m northwest of Lubhok Bay Beach site exposure (Figure 5). The abandoned track leading to the bunker appears on the western side of the map. The rounded-boulder foundation of the bunker (black arrows) fills an excavation dug into pre-bunker alluvium. The dark organic horizon (white arrows) was the surface of the alluvial fan at the time of construction. The postbunker alluvium thins southward along the seacliff and does not appear in the excavation that shows the ancient tsunami deposits. View is southward. 6 Figure S1.6. Large annotated photomosaic of the seacliff exposure at the Lubhok Bay Beach site. See PDF file. 7 2. Grain-size analysis 2.1 Methods We conducted grain-size analysis using a Beckman Coulter laser particle-size analyzer (measures grain sizes between 0 and 2000 μm) on all bulk sediment samples (~5 cm3) from the Lhok Cut and Lubhok Bay sites (Tables and Figures S2.1and S2.2, respectively). Prior to analysis, we removed organics with a solution of 20% hydrogen peroxide, then rinsed the samples with distilled water and treated them with sodium hexametaphosphate for 24 hours to disperse clays (Donato et al., 2009). Grain size values for all samples are according to the Wentworth-Phi Scale, and descriptions follow those of Blott and Pye (2001). Mean (average particle size), mode (dominant particle size), and standard deviation (degree of sorting) appear in the tables and figures. We also calculated dominant grain sizes for the 10th (d10), 50th (d50) and 90th (d90) percentiles, because reporting a range of d values illustrates well the skewness (non-Gaussian distribution) of a sediment distribution curve (e.g., fine or coarse tail) (Blott and Pye, 2001). 2.2 Results Lhok Cut site We analyzed samples from the upper four units at the Lhok Cut seacliff (Table S2.1 and Figure 4). LC 1: The thin soil that caps the sequence has a matrix of very poorly sorted (SD = 2.817ɸ) very coarse silt (mean = 4.718ɸ). LC 2: LC 2 is a man-made earthen ridge. The matrix is a very poorly-sorted (SD = 3.512ɸ) very fine silt (mean = 3.112ɸ). LC 3: The matrix of the unit overlying the tsunami deposit is a very poorly-sorted (SD = 3.430ɸ) very fine silt (mean = 8.413ɸ). LC 4: The fine-grained matrix of the tsunami deposit consists of a very poorly-sorted (SD = 2.193 ɸ) clay (mean = 10.330ɸ). Table S2.1. Grain size data for the Lhok Cut site, including mean, mode, standard deviation (SD), and d10, d50 and d90 values. Descriptions are based on the mean grain size and interpreted using the Wentworth-Phi Scale and Blott and Pye (2001). 8 Figure S2.1. Grain size data from four stratigraphic layers above the lime-plaster floor at the Lhok Cut site. Sample localities appear on Figure S1.2. SD = standard deviation (sorting). Lubhok Bay Beach site We subdivide the strata at the Lubhok Bay Beach seacliff exposure into seven units (Figure and Table S2.2). LB 1: Modern sandy soil. No grain size data. LB 2: Sampled at 47.2 cm below the modern surface, overlies LB 3 with a gradational contact that has been heavily bioturbated. The matrix of this 15-cm thick bed is similar 9 in grain size (medium silt; mean = 6.834ɸ) and sorting (SD = 3.318ɸ) to the matrix of LB 4. LB 3: LB 3 outcrops discontinuously about 62.5 cm below the surface. Its matrix is a very poorly sorted (SD = 3.143 – 3.321ɸ) coarse silt with large coral clasts. LB 4: Overlying LB 5 is a ~40-cm thick bed (LB 4), the matrix of which ranges from a very poorly sorted (SD = 3.143 to 3.053ɸ) very fine silt (mean = 8.471ɸ to 6.905ɸ) at its base to a very poorly-sorted (SD = 3.254ɸ) medium silt (mean = 6.396ɸ) at the top. LB 5: Lining much of the channel cut into LB 6 is a ~15-cm thick, black soil (LB 5b) that shows minor grading from very fine silt at the base (mean = 7.018ɸ) to clay silt at the top (mean = 9.72ɸ). Filling the channel is LB 5a, a framework-supported deposit with a sparse very poorly sorted (SD = 3.934ɸ) fine silt (SD = 6.911ɸ) matrix. The bulk of the stratum comprises abundant coral pebble clasts. LB 6: A gradational contact separates LB 7 from LB 6. LB 6 is a 30-cm thick deposit characterized by a poorly sorted (SD = 1.528ɸ) clay (mean = 10.880ɸ). LB 7: An analysis of a sample 167.5 cm below the modern surface shows that the matrix of LB 7 is a poorly-sorted (SD = 1.769ɸ) medium sand (mean = 1.622ɸ). Table S2.2. Grain-size data for the Lubhok Bay Beach site, including lithologic field descriptions, mean, mode, standard deviation (SD), and d10, d50 and d90 values. Descriptions are based on the mean grain size and interpreted using the Wentworth-Phi Scale and Blott and Pye (2001). 10 Figure S2.2. Grain size data from eleven sampling intervals within the seven stratigraphic layers at the Lubhok Bay Beach site. Sample localities are shown in Figure S1.6. SD = standard deviation (sorting). 11 3. Foraminiferal analysis 3.1 Methods We examined four samples from the Lhok Cut site for foraminiferal taxa to constrain both their ecological provenance and their taphonomy (i.e. surface weathering). The latter provides information on residence time and transport history. We dried each 510 cm3 sample at approximately 25°C before sieving to recover specimens >63 µm. We then examined the sample for foraminiferal content using a binocular microscope. Seven taxa from the taxonomy of Loeblich and Tappan (1987) exist within the samples. We categorized individual foraminifers using the same taphonomic criteria defined by Pilarczyk et al. (2011). Pristine specimens are termed “unaltered.” Specimens with rounded edges are termed “abraded” and those that are pitted are termed “corroded.” We collected 11 samples from the Lubhok Bay Beach exposure and enumerated the total number of species and recorded the presence/absence of benthic and planktic species. 3.2 Results Foraminifera are present in all examined units of both seacliff exposures, but in varying concentrations. The units of the Lhok Cut site contained higher abundances of foraminifera than the Lubhok Bay Beach site. Lhok Cut site The tsunami deposit at the Lhok Cut site contains very high concentrations of foraminifera (1160 per 10 cm3). Other layers contain far lower concentrations (40 to 70 foraminifera/10 cm3). Samples from LC 1 (LBS-11-1 0-5 cm), LC 2 (40-50 cm) and LC 3 (85-95 cm) contained low abundances of foraminifera (4 to 7 individuals/cm3), and these were predominantly abraded/corroded. This implies prolonged subaerial exposure (Table and Figure S3.1). Individuals found in these intervals are likely to have been deposited by wind. The sample from the tsunami deposit (LC 4, sample LBS 115-125 cm), contained a high concentration (1160/cm3) of foraminifera, of which, 44% of these individuals were taphonomically altered. Fragmented and abraded/corroded specimens accounted for 31% and 25%, respectively. Subtidal (Amphistegina lobifera, A. lessonii, Cibicides refulgens, Elphidium craticulatum, Palaeonummulites venosus,) and intertidal (Ammonia parkinsoniana, Asterorotalia pulchella) species predominated. All but one species found inhabit shallow (0 - 10 m) depths. However, one species (P. venosus), which constituted 14% of the assemblage has previously been found to occupy depths >20 m in Indonesian waters (Cleary and Renema, 2007). The relatively high abundance of unaltered P. venosus strongly supports a tsunamigenic source for the deposit. 12 Core ID Unit No. LBS -11-1 LC 1 LBS -11-1 LC 2 LBS -11-1 LC 3 LBS -11-1 LC 4 0-5 40-50 85-95 115-125 Species ecology 40 50 70 1160 - Ammonia parkinsoniana 40 0 0 190 intertidal (brackish); <10 m Amphistegina lessonii 0 0 0 110 subtidal; <10 m depth Amphistegina lobifera 0 30 20 310 subtidal; <10 m depth Asterorotalia pulchella 0 0 0 40 intertidal (brackish); <10 m Depth below surface (cm) Specimens per 10 cm 3 Taxonomy: Cibicides refulgens 0 0 20 130 subtidal Elphidium craticulatum 0 20 30 220 subtidal; 1-30 m depth Palaeonummulites venosus 0 0 0 160 subtidal; >20 m depth Taphonomy: Unaltered 10 0 20 510 - Fragmented 0 0 10 360 - Abraded/corroded 30 50 40 290 - Table S3.1. Foraminiferal data (taxa and taphonomy) for four samples obtained from the Lhok Cut site. 13 Figure S3.1. Dominant foraminiferal species and taphonomic characters from the Lhok Cut exposure. 14 Lubhok Bay Beach site Total foraminifera abundances are low and do not differentiate between tsunami and nontsunami sediment (Table S3.2). Benthics appear in all seven units, whereas planktics are present only in LB 3, the upper tsunami deposit. Depth below surface (cm) Unit No. Benthic sp. present? Planktic sp. present? Total specimens per 10 cm3 47.5 62.5 68.5 74.5 87.5 105.5 112.5 123.0 126.0 137.5 167.5 LB 2 LB 2/3 LB 3 LB 4 LB 4 LB 4 LB 5a LB 5b LB 5b LB 6 LB 7 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes no no yes no no no no no no no no 6 7 6 4 6 2 2 2 4 3 6 Table S3.2. Foraminiferal data for eleven samples obtained from the Lubhok Bay Beach site. 15 4. Geochemical analysis 4.1 Methods The utility of δ13C as a tracer in fluvial and marine sediments is based upon whether plants use atmospheric CO2 (terrestrial plants), dissolved CO2 or bicarbonate (HCO3) (aquatic plants and organisms) to fix carbon during photosynthesis. Ultimately, terrestrial organic matter is depleted in 13C compared to marine organic matter. Thus marine particulate and dissolved organic matter typically yield δ13C values of between 18 to -23‰, whereas freshwater particulate and dissolved organic matter show more negative δ13C values in the range of -26 to -32‰ (Deines, 1980). In theory the main source(s) of marine and terrestrial of organic matter supplied to estuarine, coastal and marine sediments can be readily determined (Kemp et al., 2010). However, in practice a number of physical processes such as tidal mixing, grain-size sorting, seasonality of river discharge, organic matter residence time and biological decay processes including bioturbation by invertebrates, fungal and bacterial decay as well as overprinting of the natural carbon signature by anthropogenic pollution may hinder such distinctions (Abril et al., 2002; Middelburg & Herman, 2007; Vane et al., 2010). Rock Eval Pyrolysis has been used to track organic carbon sources and transformations in mangrove peats and paleaolake sediments (Copard et al., 2006; Jacob et al., 2004; Marchand et al., 2008). The two most important parameters for paleoenvironmental reconstructions are thermo-vaporized free hydrocarbons (oil) expressed in mg/HC/g rock (S1) and hydrocarbons released from cracking of bound organic matter (polymers or kerogen) expressed in mg/HC/g rock (S2). The basic interpretive premise applied to the Rock Eval data is that marine/coastal sediments contain lower amounts of thermally labile organic matter (S1 and S2) than terrestrial or riverine sediments. We do not use a third Rock Eval parameter, the hydrogen index (HI = [100 × S2]/TOC) because of very low value, ranging from just 5 up to 98 (typical HI values range from 100 to 600). Stable Carbon Isotope (δ13C) and C/N For measurement of δ13C and TOC, four sediment samples from the Lhok Cut seacliff exposure and eleven from Lubhok Bay were treated with 5% HCl for 18 hours, washed with deionised water, dried in an oven at 40ºC overnight and milled to a fine powder using a pestel and mortar. Plant samples were treated with 5% HCl for 2-3 hours washed with deionised water, dried in an oven at 40ºC overnight and milled to a fine powder using a freezer mill.13C/12C analyses were performed on sediment samples by combustion in a Costech Elemental Analyser coupled on-line to an Optima dual-inlet mass spectrometer. δ13C values were calculated to the VPDB scale using a within-run laboratory standard (cellulose, Sigma Chemical prod. no. C-6413) calibrated against NBS-19 and NBS-22. TOC values were analysed on the same instrument. Replicate analysis indicated a precision of <0.1‰ (1 SD) for δ13C and TOC% (wt/wt) measurements. Rock Eval Pyrolysis Pyrolysis was performed on approximately 60 mg of powdered sediment (dry/wt) using a Rock-Eval 6 analyser (Vinci Technologies) in standard configuration (pyrolysis and oxidation as a serial process). Briefly samples were heated from 300ºC (hold 3 min) 16 to 650ºC (hold 3 min) at 25ºC/min in an inert atmosphere of N2. The residual carbon was then oxidized at 300ºC to 850ºC at 20ºC/min (hold 5 min). Hydrocarbons (HC) released during the two stage pyrolysis were measured using a flame ionization detector (FID). The CO and CO2 released during thermal cracking of the bound organic matter (OM) was monitored using an IR cell. The performance of the instrument was checked every 10 samples against the accepted values of Institut Français du Pétrole (IFP) standard (IFP 160 000, S/N1 5-081840). 4.2 Results Lhok Cut site Sediments from Lhok Cut seacliff exposure show δ13C values in the range of-24.3 to -23.8 which suggests little variation in organic matter source through the section (Table S4.1; Figure S4.1). In general marine organic matter yield δ13C of -18 to -23‰ whereas terrestrial organic matter show more negative δ13C values in the range of -26 to 32‰. Thus the values obtained here lie between the two suggesting possibly mixed source(s). TOC values increased from <0.9 % (125 to 40 cm) up to 2.4 % (2.5cm) which perhaps, gives credence to the notion that the uppermost interval (0-5 cm) has either a different source of organic matter or that has undergone less diagnetic alteration than the lower intervals. Similarly, the simultaneous rise in HI from <50 to >100 mg/HCgTOC and S2 parameter (concentration of bound hydrocarbons) suggest a change in organic matter source. Depth below surface (cm) 2.5 45.0 90.0 120.0 Unit No. LC 1 LC 2 LC 3 LC 4 S1 (mg/g) S2 (mg/g) TOC (%) HI δ13C 0.17 0.02 0.02 0.02 2.81 0.34 0.21 0.37 2.38 0.76 0.39 0.89 118 38 56 39 -20.2 -24.1 -25.2 -24.9 Table S4.1. Geochemical data for the Lhok Cut site. 17 Figure S4.1. Geochemical data for the Lhok Cut site. Lubhok Bay Beach site From the base of the Lubhok Bay Beach seacliff exposure (170 cm to 135 cm depth; LB 7 and lower portion of LB 6) the δ13C down values range from -23.2 to -21.6‰ and show very low TOC values ranging from 0.1 to 0.4%. In contrast the overlying sediment interval (128 to 121 cm depth; includes LB 5b channel soil) shows less negative δ13C values (-19.5 to -18‰) and maximal TOC values of 0.78% (wt/wt) (Figure and Table S4.2 S4.2). The increase in TOC between is in complete agreement with the visual observation of a palaeo-soil. There isn’t a parallel shift to more negative δ13C values of > -26‰ that would usually be associated with soils comprised in part of partially decomposed C3 plant biomass and humic C3 terrestrial organic matter is not shown. One plausible explanation for the more positive δ13C values (~ 19‰) could be that the soil (catchment) was dominated by either C4 or CAM plants. Between 115 to 110 cm depth (LB 5a lower tsunami deposit) the δ13C is -20.7‰ and TOC is 0.3 %. The three sediment intervals between 108 up to 71 cm depth (LB 4) show rather invariant δ13C values of ~22‰ and TOC values ranging from 0.2 to 0.5 %. The shift back to marine sourced organic matter is then reflected at 70 to 67 cm core depth (LB 3 upper coral rubble) by a δ13C of -19.2‰. The upper two intervals from -65 to 45 cm depth (LB 2 and the diffuse contact with LB 3) represent a transition to very high δ13C values but slightly greater TOC values than the underlying coral rubble. The δ13C values from the seacliff exposure suggest a marine origin for all layers (marine organic matter δ13C values range -18 to -24‰). Our interpretations are in part supported by analysis of a single sample of known marine origin (UBK-B-4 Trench) which gave somewhat similar negative δ13C value of -23.9‰ and TOC of 0.3 %. 18 The S1 and S2 profiles deviate to low values similar to that of the marine endmembers at -170 to -165 cm (LB 7), -125 to -110 cm (includes LB 5) and between 77 to 60 cm (includes LB 3; Table S4.2; Figure S4.2). This suggests that these sediment intervals have received some marine organic matter. Depth below surface (cm) Unit No. 47.5 62.5 68.5 74.5 87.5 105.5 112.5 123.0 126.0 137.5 167.5 LB 2 LB 2/3 LB 3 LB 4 LB 4 LB 4 LB 5 LB 5 LB 5 LB 6 LB 7 S1 (mg/g) S2 (mg/g) TOC (%) HI δ13C 0.07 0.02 0.01 0.02 0.03 0.04 0.01 0.01 0.01 0.04 0.01 0.47 0.2 0.17 0.16 0.28 0.42 0.07 0.04 0.08 0.25 0.04 0.48 0.23 0.21 0.20 0.34 0.51 0.26 0.78 0.33 0.36 0.10 98 87 81 80 82 82 27 5 24 69 40 -14.1 -18.6 -19.2 -22.6 -22.3 -22.7 -20.7 -18.9 -19.5 -21.6 -23.2 Table S4.2. Geochemical data for Lubhok Bay Beach site. 19 Figure S4.2. Stable carbon isotope (δ13C), total organic carbon (TOC), free and bound hydrocarbon concentration and hydrogen index for the Lubhok Bay Beach site. 20 5. Geochronological analyses This section contains all the documentation of dates that appear in the paper. The first section contains radiocarbon analyses. The second contains Uranium-Thorium analyses. In each section, the analyses for the Lhok Cut site appear first and the analyses for Lubhok Bay appear second. The Lubhok Bay data include radiocarbon and U-Th analyses conducted on materials from Fort Lubhok, about 200 hundred meters southeast along the coast from the seacliff exposure that we mapped (Figure 7). For lack of space, we do not discuss these dates in the paper, but present them here, so that they will be available to future researchers. We did not find suitable materials to date the man-made earthen ridge or mound at the Lhok Cut site (Figures 2, 3 and 4). Nor were we able to find materials within the uppermost, cobbly unit at the Lubhok Bay Beach seacliff exposure (Figures 7 and 8), which we suspect to have resulted from accelerated erosion after construction of the dirt road above the site. We suspect that these layers and landforms are contemporaneous with the construction of the two forts on Lamreh peninsula, the Fort of the Widows above Lhok Cut and Fort Lubhok on Lubhok Bay (Figure 2). Edwards McKinnon [2009] argues that these forts and several other stone structures between the peninsula and Banda Aceh were constructed in the early decades of the Aceh sultanate, specifically in the middle of the 16th century. If so, then their construction dates would provide a minimum age for the tsunami deposits within our exposures. 5.1 Radiocarbon analysis 5.1.1 Methods All radiocarbon samples were analyzed by Beta Analytic Inc, Miami, Florida, using accelerator mass spectrometry. 5.1.2 Results Lhok Cut site Sample Material: number Pre(LAMBS1- treatment ) 21 tooth: collagen extraction: with alkali 20 charred material: acid/alkali/aci d Measured Age (BP) 590 +/- 30 640 +/- 40 13C/12C Convention 2 Sigma (‰) al Calibration Age (BP) (Common Era) -19.8 680 +/- 30 1270-1310 and 13601390 -21.6 700 +/- 40 1260-1310 and 13601390 21 19 18 17 16 13 12 11 8 6 bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali bone collagen: collagen extraction with alkali tooth: collagen extraction: with alkali bone collagen: collagen extraction with alkali 590 +/- 30 -16.8 720 +/- 30 1260-1300 610 +/- 30 -14.6 780 +/- 30 1210-1280 520 +/- 30 -9.0 780 +/- 30 1210-1280 700 +/- 30 -19.1 800 +/- 30 1200-1270 590 +/- 40 -19.4 680 +/- 40 1270-1320 and 13501390 460 +/- 40 -9.4 720 +/- 40 1240-1300 and 13701380 600 +/- 40 -20.1 680 +/- 40 1270-1320 and 1350-1390 410 +/- 40 -7.3 700 +/- 40 1260-1310 and 13601390 640 +/- 40 -18.8 740 +/- 40 1220-1300 22 3 bone 320 +/- 40 -9.3 580 +/- 40 1300-1430 collagen: collagen extraction with alkali 2 bone 440 +/- 40 -13.8 620 +/- 40 1280-1410 collagen: collagen extraction with alkali Table S5.1. Radiocarbon analyses for the Lhok Cut seacliff exposure, which appear in Figure 4. Lubhok Bay Beach site Sample Material: number Pre-treatment (LMR 10-B-) Measured Age (BP) 13C/12C (‰) Conventional Age (BP) AM6a organic sediment: acid washes 810 +/- 30 -17.9 930 +/- 30 2 Sigma Calibration (Common Era) 1030-1170 7a charred material: acid/alkali/acid 1050 +/- 40 -24.6 1060 +/- 40 890-1030 6b charred material: acid/alkali/acid 800 +/- 40 -25.6 790 +/-40 1170-1280 6a charred material: acid/alkali/acid 980 +/- 40 -24.3 990 +/- 40 980-1160 4b2 charred material: acid/alkali/acid 510 +/- 40 -23.1 540 +/- 40 1310-1360 and 13901440 Table S5.2. Radiocarbon analyses for the Lubhok Bay Beach site, which appear in the map of the Lubhok Bay Beach seacliff exposure (Figure 6). 23 Kuta (Fort) Lubhok The loose lime mortar used in construction of Fort Lubhok contains abundant angular, small pebbly clasts of charcoal. This charcoal likely derives from wood fires used to create the lime mortar from nearby deposits of limestone. Hence its age should be the age of the wood used to fuel the fires. Since it would have been easier to cut younger rather than older trees, it could well be that the radiocarbon ages of the charcoal are within a decade or so of the date of construction of the fort. Table S5.3 displays three dates from charcoal within the mortar of the main wall of the fort. All three come from a location near the base of the wall and within ten or so centimeters from its seaward face. Note that two of the analyses (LK13-A1-A and G) yielded date ranges that suggest construction of the fort between 1490 and 1650 CE, consistent with construction within the first century and a half of the Aceh sultanate. The third sample (LK13-A1-B) yielded an age within the younger ranges of 1640-1670 and 1780-1800 (The third range for this analysis – 1940-1950 – is of course not plausible). We suggest that the two earlier age ranges bracket the date of construction of the fort. The one younger date could well reflect repair of the loose lime mortar at a later date, something that was common for structures held together with weak lime mortar. Sample number (LK13-) Material: Pre-treatment Measured Age (BP) A1-A charred material: acid/alkali/acid 300 +/- 30 A1-B charred material: acid/alkali/acid 170 +/- 30 A1-G charred material: acid/alkali/acid 300 +/- 30 13C/12C Conventional 2 Sigma (‰) Age (BP) Calibration (Common Era) -20.5 370 +/- 30 1450-1530 and 15401630 -20.8 240 +/- 30 1640-1670, 1780-1800 and 19401950 -24.7 300 +/- 30 1490-1600 and 16101650 Table S5.3. Radiocarbon analyses of charcoal from the lime mortar of Fort Lubhok. 24 5.2 U-Th analysis 5.2.1 Methods All coral fossil samples were selected for U-Th chemistry (Shen et al., 2003) and isotopic measurements on a multi-collector inductively coupled 4 plasma mass spectrometer (MC-ICP-MS), Thermo Electron Neptune, at the HISPEC Laboratory, Department of Geosciences, National Taiwan University (Shen et al., 2012) and at the Earth Observatory of Singapore, Nanyang Technological University. A gravimetricallycalibrated triple-spike, 229Th-233U-236U, isotope dilution method (Cheng et al., 2013) was employed to correct mass bias and determine uranium concentration. U-Th isotopic compositions and concentrations and dates are listed in the tables that follow. All measured isotopic uncertainties and date errors given are two standard deviations unless otherwise noted. 5.2.2 Results Table S5.4. Analysis of pristine coral cobble from the foundation beneath the lime plaster floor of the earthen mound at Lhok Cut. Table S5.5. Analyses of large-corallite corals from Fort Lubhok (Figure 2) and a Goniastrea retiformis from the Lubhok Bay Beach seacliff exposure. 25 Table S5.6. U-Th analyses of Porites sp. samples from the Lubhok Bay Beach Site. Two of the samples yielded isochron ages, whereas the other yielded an age based upon averaging of several analyses. 26 5.2.3 Initial Thorium assumptions Both uncorrected and corrected ages appear in Table S5.6. Corrected age reflects removal of the contribution of non-radiogenic 230Th (also called detrital 230Th) by assuming an initial 230Th/232Th ratio. The higher the Th concentration, the larger the correction. For instance, the corrected ages of coral samples with 5-14 ppb Th in our corals can easily cause the corrected age to be more than one decade younger, even if the initial 230Th/232Th ratio deviated by just 1 ppm from what we got from the isochron (that is, 8.6 ppm in Table S5.7). The isochron technique undoubtedly helps to constrain the initial 230Th/232Th ratio, but assumes a simplified two-end-member model, which we know might not always be valid. Thus the isochron calculation may not yield an accurate initial Th value. Thus, ages one to two decades older than the expected age of AD 1393±2 may well be the result of incorrectly modeled corrections. [Th] Corrected age (AD) by different initial 230Th/232Th value 8.6 ppm 9.6 ppm Uncorrected age (AD) 10.6 ppm 5 ppb 1353 ± 16.3 1365 ± 16.3 1377 ± 16.3 1247 ± 9.2 9 ppb 1325 ± 33.0 1353 ± 32.8 1380 ± 32.8 1089 ± 12.9 14 ppb 1333 ± 52.9 1377 ± 52.9 1422 ± 52.9 951 ± 20.1 Table S5.7. 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