Investigating the final cause of the catastrophic flooding of , Rebecca Bateman | Supervisor: Dr. Tim Kinnaird | University of St Andrews

ELF003 PROFILE

STORED DOSE ELF003 0. 00 20. 00 40. 00 60. 00 From sedimentology studies, the core was divided 0 into marine sands (0-92cm), mudflats (92-311cm), What were we setting out to look at? sands (311-335cm) and reworked till (335-341cm). Doggerland was a land corridor sitting The sands between 311 and 335cm have been between Britain and continental Europe. 50 interpreted as either high energy storm beach Around 8,150 years ago, Doggerland was deposits or the deposits related to the . This is highlighted in figure A. finally submerged. There are two theories Marine Sands for the cause of the submersion: 100 • The Storegga tsunami, the worst Preliminary Screening natural disaster thought to hit To begin with I produced single aliquot Scotland in the last 10,000 years measurements along the length of core ELF003. 150 (Fruergaard, et al., 2015). These were analysed in RISO analyst, and used to • Sea level rises from the melting of identify sub-samples from the core for further

the Laurentide ice sheet (Hill, et al., investigation. Figure B. shows stored dose vs depth. DEPTH (CM) DEPTH 2017). 200 The equivalent dose ( also referred to as stored dose) represents the stored charge in the quartz on the The project seeks to interpret the aliquot built up by background radioactivity whilst processes and timing of when buried. Typically, the greater the dose, the older the 250 Doggerland was finally submerged using represented sample is. Optically Stimulated Luminescence (OSL) profiling and dating methods. • The marine sands show a stratigraphic 311m to 300 Gaffney et al. 2020 identified deposits Mudflats progression . 335m is shelly • The mudflats are poorly bleached, and show related to the tsunami in core ELF001a. sand with, High energy sand deposit They identified cores ELF003 as potential some small significant scatter from ~4 to 24 Gy. candidates for also containing historical clasts <1cm, 350 Reworked till • The sands between 311 and 335 cm also have a evidence of the tsunami. and bivalves. stratigraphic signature, promising for dating MeanMean Paleodose dose per depth

Figure A: Photograph of core ELF003 Figure B: Store dose profile of core ELF003 STORED DOSE SENSITIVITY EQUIVALENT DOSE OF 39. 0. 00 10. 00 20. 00 30. 00 1000 10000 EACH SAMPLE 285 285 Equivalent Dose Central Dose 290 290 DOSE 295 295 5.00 10.00 15.00 20.00 25.00 305

300 300 39. 310 40. 305 305 40. 315

310 39. 310 DEPTH (CM) DEPTH DEPTH (CM) DEPTH 40.

315 315 (CM) DEPTH 320 42. 320 320 325 42. 325 325 43. 42. 330 43. 330 330 Figure D: Plot of equivalent doses of each sub- sample taken 335 335 Weighted Mean Central Age Model Figure C: Sub-section of the profile of core ELF003 seen in figure B. Unweighted Mean Common Age Model

Figure C. shows the same profile as B., but enlarges the section from 275cm to 335cm. There are two 43. values for all depths, but in the sands both doses are very similar and they overlap. Sub-samples taken for further final analysis were ELF003/39, ELF003/40, ELF003/42 and ELF003/43.

Equivalent dose determinations Equivalent doses were determined on 24 aliquots of quartz using a single aliquot regenerative dose (SAR) OSL procedure. Figures D and E show the equivalent dose distributions obtained for each sample these are shown as Kernel density estimation (KDE) plot (left) and Abanico plots (right). I explored several dose models and these are represented by coloured lines on figure E. Figure E: KDE and Abanico plots for each sub-sample of ELF003 Weighted Mean Central Dose Common Dose Figure F: Table of different age models Method Mean Method Method Method

Depth Dose Dose Rate Model 3 Model Model 2 Model (cm) Rate Error Age (ka) Error Age (ka) Error Age (ka) Error Age (ka) Error 39 309 1.454 0.194 6.95 1.41 7.87 1.02 7.62 1.56 7.33 1.42 40 312 1.333 0.177 6.28 1.2 7.52 0.98 7.45 1.5 6.88 1.22 42 323 0.793 0.092 11.37 1.17 13.17 1.53 12.61 1.4 12.57 1.16 43 328 0.965 0.099 8.44 0.93 10.87 1.05 10.23 1.18 9.28 0.93

Central Dose (Ka) SD [Ka] OD [%] Central Dose (Ka) SD [Ka] OD [%] Combined Combined Model 2 7.54 0.32 21.2 Model 3 11.37 0.46 30.98 Figure I + J: Table of Central Age values for combined Model 2 and Combined Model 3.

Figure G: KDE and Abanico plots for select combined models. Age determinations and conclusions A luminescence age is calculated as the quotient of the stored dose (in Gy) divided by the dose rate (in mGy a-3). Figure F. presents the different age estimates that are determined using four different models for assimilating equivalent doses: mean, weighted mean, central dose and common doses. For 39: 7.62 ± 1.56 ka age determinations, the central dose model was selected. • The final inundation of Doggerland was approximately around 7.45 ± 1.5 ka and 7.62 ± 1.56 ka (ELF003/40 and ELF003/39 respectively), as these sit on the transition between terrestrial and marine. This shows that final inundation was caused by sea level change, and not the Storegga tsunami. • The beach sands at the base of the core (311- 335cm) were probably deposited at around 12.61 ± 1.4 and 10.23 ± 1.18 ka. (ELF003/42 and SILTS 311cm ELF003/43 respectively), long before the Storegga tsunami. SAND Weighted combinations of ages Future Work Different statistical approaches for combining I am now exploring ELF059, another core identified as potentially recording the Storegga tsunami. 40: 7.45 ± 1.5 ka the equivalent doses and corresponding age For this core, I will follow the same procedures to establish relationships between Doggerland’s estimates for several groupings of the date were inundation and the tsunami. explored: • Model 1: ELF003/40, EF003/42, Acknowledgements: 42: 12.61 ± 1.4 ka ELF003/43 combined. This research was supported by a Carnegie Trust Vacation Scholarship to Rebecca Bateman • Model 2: ELF003/39, ELF003/40 combined. (ref: VAC009630) Additional thanks to the Lost Frontiers Project for their support. • Model 3: ElF003/42, ELF003/43 combined. References: Using this approach final inundation most Fruergaard, M. et al., 2015. Tsunami propagation over a wide, shallow caused by the Storegga slide, southeastern probably occurred at 7.54 ± 0.32 ka (Model 2), North Sea, Denmark. Geology, 43(12), p. 1047–1050. and the sands at the base accumulated between Gaffney et al, 2020. Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the 43: 10.23 ± 1.18 ka Southern North Sea, Geoscience, 10, 270 11.37 ± 0.46 ka (Model 3) and inundation. Hill, J. et al., 2017. Was Doggerland catastrophically flooded by the Mesolithic Storegga tsunami?, Physics Figure H: diagram showing ages relative to depths within core ELF003.