***Luminescence dating results from the research project: Subsurface stratigraphic controls on subsidence and carbon sequestration in Mississippi Delta diversion receiving basins***
Authors: E.L. Chamberlain, L. van der Lee
Soil Geography & Landscape group and Netherlands Centre for Luminescence dating, Wageningen University and Research
Contact: liz.chamberlain@wur.nl
***General introduction***
This excel file contains optically stimulated luminescence (OSL) dating results for sedimentary deposits of Barataria Bay, Louisiana (U.S.). The ages were produced using standard procedures to date quartz sand grains extracted from the sediment samples. The luminescence dating was performed at the Netherlands Centre for Luminescence dating (NCL) of Wageningen University. This work is part of a project funded by the RESTORE Act Center for Excellence for Louisiana entitled Subsurface stratigraphic controls on subsidence and carbon sequestration in Mississippi Delta diversion receiving basins.
***Methodology***
For paleodose estimation, purified quartz sand of the desired grain size was obtained through wet sieving, treatment with hydrogen peroxide and hydrochloric acid, separation at 2.67 kg/cm3 and 2.63 kg/cm3 in a high-density liquid, and treatment with hydrofluoric acid. Optically stimulated luminescence signals were measured on a Riso TL/OSL DA-15 or DA-20  using the Single Aliquot Regenerative (SAR) dose procedure (Murray and Wintle, 2003). Signals and backgrounds were integrated using the Early Background approach (Cunningham and Wallinga, 2010). Measurements were repeated on 48 1-mm diameter aliquots per sample if sufficient sand was available. Aliquot acceptance criteria included a test dose error of less than 20%, recuperation less than 10% of the greatest regenerative dose, and recycling ratios of less than 10%, including one test for infrared (IR) depletion (Duller, 2003). The SAR protocol was validated with dose-recovery and thermal-transfer tests. The paleodose of each sample was obtained using the bootstrapped version (Cunningham and Wallinga, 2012) of the Minimum Age Model (Galbraith et al., 1999) with a sigma_b input of 9.5  3.0 (Chamberlain et al., 2018a; Chamberlain et al., 2018b). 
For dose rate estimation, radionuclide activities were obtained from bulk sediment using a gamma spectrometer or MuDose instrument. Water content was assumed to be 40% dry weight for muds and 35% dry weight for sands with 10% relative uncertainty. In situ organic contents were determined through ashing and 10% relative uncertainty was assumed. The dose rate includes an internal alpha dose of 0.010  0.005 Gy/ka in dose rate calculation (Vandenberghe et al., 2008). Cosmogenic contributions were determined following Prescott and Hutton (1994); grain-size attenuation was determined following Mejdahl (1979), and attenuation by water content and organics was determined following Aitken (1998).
Luminescence ages were determined by dividing the paleodose by the dose rate for each sample. 
***Data specific information***
The data set consists of 5 data tables in excel. 
Data table 1 provides a description of the boreholes and OSL samples taken from each borehole. The headers for each column in Data table 1 are: Borehole, TU; Borehole, LSU; Modern environment; Interpretation; Date of coring; Latitude; Longitude; Surface elevation (m, NAVD88); Water depth to core (m); Hand core depth (m); Vibracore 1 depth (m); Vibracore 1 length (m); Vibracore 1 compaction (m); Vibracore 2 depth (m); Vibracore 2 length (m); Vibracore 2 compaction (m); Core sampled; OSL samples. 
Data table 2 provides an OSL sample inventory. The headers for each column in Data table 2 are: Sample; Borehole, TU; Borehole, LSU; Surface elevation (m, NAVD88); Depth in core (m) (estimated); Depth in vibracore (m); Water depth to core (m); Sample elevation (m, NAVD88); Lithologic unit; Clastic Overburden thickness (m) (estimated)	; Organic overburden thickness (m) (estimated); Clastic Overburden thickness in vibracore (m); Organic overburden thickness in vibracore (m). 
Data table 3 provides a summary of the OSL dating results. The headers for each column in Data table 3 are: Sample; Borehole, TU; Borehole, LSU; Uncompacted depth in core (m); Elevation (m, NAVD88); Grain size fraction (microns); Accepted aliquots (n)	; Paleodose (Gy); Age model; Dose rate (Gy/ka); Age (ka); Validity judgement. 
Data table 4 provides the dose rate details. The headers for each column in Data table 4 are: Sample; In situ water content (%); Estimated water content (%); In situ organic content (%); U (Bq/kg); Th (Bq/kg); 40K (Bq/kg); Machine; Burial regime; Cosmogenic dose (Gy/ka); Dose rate (Gy/ka). 
Data table 5 provides age model results. The headers for each column in Data table 5 are: Sample; Grain size; Bootmam (9.5 +- 3% sigma_b); De (Gy); CAM De (Gy); CAM OD (%); Iterated mean (2 SD) (Gy); Aliquots measured; Aliquots accepted; Aliquots excluded by iteration. 
Units of measurement are: meters (m) for depths and elevations, with elevations relative to North American Vertical Datum 1988 (NAVD88); Becquerels per kilogram (Bq/kg) for radioactivity; Gray per thousand year (Gy/ka) for dose rate; percent (%) for water and organic contents and overdispersion; Gray (Gy) for paleodose and equivalent dose; thousand years (ka) relative to 2022 for age. 
Other abbreviations are: TU for Tulane University; LSU for Louisiana State University; U for uranium; Th for thorium; 40K for potassium-40; Bootmam for the bootstrapped minimum age model; CAM for the central age model; De for equivalent dose; OD for overdispersion. 
***References***
Aitken, M.J., 1998. An introduction to optical dating: the dating of Quaternary sediments by the use of photon-stimulated luminescence. Oxford University Press, London.
Chamberlain, E.L., Trnqvist, T.E., Shen, Z., Mauz, B., Wallinga, J., 2018a. Anatomy of Mississippi Delta growth and its implications for coastal restoration. Science Advances 4, eaar4740.
Chamberlain, E.L., Wallinga, J., Shen, Z., 2018b. Luminescence age modeling of variably-bleached sediment: Model selection and input. Radiat Meas 120, 221-227.
Cunningham, A.C., Wallinga, J., 2010. Selection of integration time intervals for quartz OSL decay curves. Quat Geochronol 5, 657-666.
Cunningham, A.C., Wallinga, J., 2012. Realizing the potential of fluvial archives using robust OSL chronologies. Quat Geochronol 12, 98-106.
Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H., Olley, J.M., 1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part I, experimental design and statistical models. Archaeometry 41, 339-364.
Mejdahl, V., 1979. Thermoluminescence Dating - Beta-Dose Attenuation in Quartz Grains. Archaeometry 21, 61-72.
Murray, A.S., Wintle, A.G., 2003. The single aliquot regenerative dose protocol: potential for improvements in reliability. Radiat Meas 37, 377-381.
Prescott, J.R., Hutton, J.T., 1994. Cosmic-Ray Contributions to Dose-Rates for Luminescence and Esr Dating - Large Depths and Long-Term Time Variations. Radiat Meas 23, 497-500.
Vandenberghe, D., De Corte, F., Buylaert, J.-P., Ku?era, J., 2008. On the internal radioactivity in quartz. Radiat Meas 43, 771-775.

