Heavy mineral assemblages of the Storegga tsunami deposit

Cascalho, João; Costa, Pedro; Dawson, Sue; Milne, F.; Rocha, Álvaro

doi:10.1016/j.sedgeo.2016.01.007

Cited by 26 publications

(20 citation statements)

References 31 publications

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“…Thus, Cascalho et al 2014) and McCarroll et al (2018) observed grain-size sorting in the course of aeolian overpass processes, where the blowout material from the beaches became finer with distance and elevation above sea level. This was partly also associated with particle density sorting (Cascalho et al 2016;Ribeiro 2017). In the present case, overpassing was (is) not associated with additional grain-size sorting as the aeolian source material was already optimally sorted.…”

Section: Sedimentological Aspectsmentioning

confidence: 94%

Sedimentology of a coastal shelf sector characterised by multiple bedload boundaries: Plettenberg Bay, inner Agulhas Bank, South Africa

Flemming

Martin²

2021

Geo-Mar Lett

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The study deals with a large sand body (spit-bar) attached to the eastern tip of the Robberg Peninsula, Plettenberg Bay, South Africa. To date, the bar has prograded about 8 km beyond the tip of the peninsula. The bar top is predominantly composed of medium sand, the upper slope of fine sand, and the lower slope of fine muddy sand. Stratigraphically, the sedimentology thus documents an upward coarsening, calcareous quartz-arenitic depositional sequence. The spit-bar as a whole forms the eastern end of a sediment compartment that is clearly distinguishable from neighbouring compartments on the basis of its geomorphology, the textural characteristics of the sediment, and the distribution of sediment thicknesses. Aeolian overpass across the peninsula appears to have formed a fan-like sand deposit in its rear, which is perched upon the upper shoreface of the bay as suggested by the bathymetry to the north of the peninsula. It forms an integral part of the sediment body defining the spit-bar. The estimated volume of sand stored in the spit-bar amounts to 5.815 km3, of which 0.22 km3 is contributed by the aeolian overpass sand. The sediment sources of the spit-bar are located up to 100 km to the west, where a number of small rivers supply limited amounts of sediment to the sea and numerous coastal aeolianite ridges in the Wilderness embayment have been subject to erosion after becoming drowned in the course of the postglacial sea-level rise since about 12 ky BP. By contrast, the sediment volume in the adjacent compartment B to the north (Plettenberg Bay), which has been supplied by local rivers, amounts to only 0.127 km3. In a geological context, large sand bodies such as the Robberg spit-bar are excellent exploration models for hydrocarbons (oil and gas).

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Section: Sedimentological Aspectsmentioning

confidence: 94%

Sedimentology of a coastal shelf sector characterised by multiple bedload boundaries: Plettenberg Bay, inner Agulhas Bank, South Africa

Flemming

Martin²

2021

Geo-Mar Lett

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“…Changing sedimentation rates or event layers were considered in the model according to Blaauw and Christen (2011) (Table S3). For the discussion, late Holocene 14…”

Section: Laboratory Methodsmentioning

confidence: 99%

The late Holocene tsunami in the Shetland Islands (UK) identified in Loch Flugarth, north Mainland

Engel

Hess

Dawson

et al. 2023

Preprint

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To assess the long-term hazard of tsunamis, particularly in regions with a short and fragmented historical record, sedimentary deposits of tsunamis are an essential tool. In the North Sea region, evidence of tsunamis is scarce. The Shetland Islands are an exception, as they contain abundant deposits of the Storegga tsunami (c. 8150 cal. a BP), and additionally more fragmented evidence of younger tsunami events c. 5500 and c. 1500 cal. a BP. Sediments of the youngest tsunami (the “Dury Voe” event) have only been found at two sites so far, marked by thin landward fining and landward thinning sand sheets which are vertically confined by peat. Here, we present sedimentary evidence for the youngest Shetland tsunami from the small coastal lake of Loch Flugarth, northern Mainland. Three gravity cores of up to 91.7 cm length were taken behind the barrier separating the lake from a shallow marine embayment. The cores show organic-rich background deposition with many sub-cm-scale sand layers, reflecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal zone. A basal 13 cm-thick sand layer, dated to 426–787 cal. a CE based on 14C, 137Cs and Bayesian age-depth modelling, was found in all three cores. High-resolution grain-size analysis identified four normally graded sublayers with inversely graded traction carpets in the lower part of two sublayers. An organic-rich ‘mud’ drape and ‘mud’ cap cover the upper two sublayers, which also contain small rip-up clasts. Grain-size distributions show a difference between the basal sand layer and the coarser and better sorted thin storm layers. Principal component analysis of X-ray fluorescence core scanning data also distinguishes both sand units: Zr, Fe and Ti dominate the basal sand, while the thin storm layers are high in K and Si. The enrichment of the basal sand layer in Zr and Ti, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content in the basal sand reflecting the additional marine sediment source of a tsunami deposit below the storm-wave base. Based on reinterpretation of chronological data from the two published sites and the chronostratigraphy of the present study, the Dury Voe tsunami seems to be slightly younger, i.e., closer to 1400 cal. a BP. Although the source of the tsunami remains unclear, the lack of evidence for this event outside of the Shetlands suggests that it was smaller than the older Storegga tsunami, which affected most of the North Sea basin.

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“…The principles applied for identification through optical properties of minerals are those given by Mange and Wright (2007) and Limonta (2014). Percentages of light and heavy minerals were counted without taking opaques, anhydrates and carbonates into account (Cascalho et al 2016). Opaque minerals were investigated individually using the ore microscope (reflection system) following the mineral description given by Bowles et al (2011).…”

Section: Methodsmentioning

confidence: 99%

Mineral Evaluation of Some Soils Representing the Geomrphic Units in the Northwestern Coast of Egypt.

Bahnasawy¹

2018

Egypt.J. Soil Sci.

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Heavy mineral assemblages of the Storegga tsunami deposit

Cited by 26 publications

References 31 publications

Sedimentology of a coastal shelf sector characterised by multiple bedload boundaries: Plettenberg Bay, inner Agulhas Bank, South Africa

Sedimentology of a coastal shelf sector characterised by multiple bedload boundaries: Plettenberg Bay, inner Agulhas Bank, South Africa

The late Holocene tsunami in the Shetland Islands (UK) identified in Loch Flugarth, north Mainland

Mineral Evaluation of Some Soils Representing the Geomrphic Units in the Northwestern Coast of Egypt.

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