Table 3 Radiocarbon dates are presented as conventional radiocarbon and uncalibrated measured AMS ¹⁴C ages, with information on the dated material and its geographical location.

Sample code	Longitude (X)	Latitude (Y)	Relative stratigraphic depth (cm)	Measured AMS ¹⁴C age in BP^a	Error (year)	Calibration curve	Delta R (year)	Delta R Error (year)	Conventional radiocarbon age (BP)	Calibrated age in BP^b (2σ)	Calibrated age in BP^b (1σ)	Significance for event chronology
21JE125A	− 70.6891	18.4281	532	1600	± 30 BP	MARINE20	− 161	± 24	2030 ± 30 BP	1746–1430	1681–1530	pre−E3
22BF03F	− 70.6897	18.4279	458	1690	± 30 BP	MARINE20	− 161	± 24	2100 ± 30 BP	1850–1530	1770–1604	pre−E3
22BF02FC	− 70.6895	18.4281	376	1850	± 30 BP	MARINE20	− 161	± 24	2260 ± 30 BP	2048–1714	1972–1803	pre−E2
22JE10C	− 70.6896	18.4280	312	1860	± 30 BP	MARINE20	− 161	± 24	2270 ± 30 BP	2063–1724	1982–1814	pre−E2
22BF02FD	− 70.6895	18.4281	174	1900	± 30 BP	MARINE20	− 161	± 24	2330 ± 30 BP	2142–1802	2056–1881	pre−E1
22JE10A	− 70.6896	18.4279	118	1890	± 30 BP	MARINE20	− 161	± 24	2330 ± 30 BP	2268–1932	2180–2008	pre−E1
22JE10B	− 70.6896	18.4279	78	2150	± 30 BP	MARINE20	− 161	± 24	2560 ± 30 BP	2426–2082	2332–2171	pre−E1

Quality assurance measurements
Reference material 1
Expected value	0.44 ± 0.04 pMC
Measured value	0.44 ± 0.04 pMC
Agreement	Accepted
Reference material 2
Expected value	129.41 ± 0.06 pMC
Measured value	129.43 ± 0.39 pMC
Agreement	Accepted
Reference material 3
Expected value	96.69 ± 0.50 pMC
Measured value	96.89 ± 0.30 pMC
Agreement	Accepted

Known-value reference materials were analyzed quasi-simultaneously with the unknowns.
Results are reported as expected values versus measured values.
Reported values are calculated relative to NIST SRM-4990C and corrected for isotopic fractionation.
Results are reported using the direct analytical measure percent modern carbon (pMC) with one relative standard deviation.
Agreement between expected and measured values is taken as being within 2σ agreement (error × 2) to account for total laboratory error.
Dated material are shells of marine bivalve mollusks. Radiocarbon dating was performed at the beta analytic laboratory.
^aConventional radiocarbon age in years before present (BP), where “present” is AD 1950, without δ ¹³C correction.
^bCalibrated ages have been calculated using the Radiocarbon Calibration Program BetaCal4.20 and the Marine20 calibration curve, with Delta-R = − 161 ± 24 derived for marine samples²⁹. Age ranges are given at 2σ (95.4%) probability level. The reported results are accredited to ISO/IEC 17,025:2017 Testing Accreditation PJLA #59,423 standards.

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