Sedimentary evolution of the north Norfolk barrier coastline in the context of Holocene sea-level change

Abstract

Holocene sediments of the north Norfolk coast (NNC) between Weybourne and Hunstanton have been studied using geophysical, sedimentological, biofacial and dating techniques. New cores and refraction seismic data have defined the topography of the pre-Holocene surface and show that the NNC sediment prism is underlain by an east-west trending Quaternary trough, probably a palaeo-river-valley. The age of the Holocene fill has been dated using radiocarbon and luminescence dates, while sedimentation rates were constrained by, and compared with, modern rates using radionuclide data. The Holocene sediments are divided into a sandy-barrier lithofacies association (LFA), and a muddy-silty-peat back-barrier LFA. The oldest Holocene sediments are peats, formed on an undulating till surface. These peats were forming by 11-10 cal. ka bp and continued to form until at least 7 cal. ka bp in a number of places. As Holocene sea-level rose, marine mudflat and saltmarsh environments began to form between 7 and 6 cal. ka bp east of Holkham and around 6 cal. ka bp or younger west of Holkham. A marked erosion surface between the barrier and back-barrier LFA in the Holkham to Burnham Overy area is imperfectly dated at <3 cal. ka bp, but suggests the sediment prism has thinned by about 3 km over 6 to c. 3cal. ka bp. This surface probably records the westward progress of laterally migrating tidal channels that caused back-barrier sediment erosion, along with shoreface processes, as sea-level rose. Small-scale regressive and transgressive saltmarsh sequences occur at different elevations along strike but cannot be correlated, suggesting that the control on saltmarsh and mudflat development is autocyclic rather than allocyclic. Generally, transgressive and regressive events are related to disposition of coastal barriers and these are superimposed on a general facies evolution governed by regional sea-level change. Predictions about how this barrier coastline might respond to increased rates of regional sea-level change caused by global warming, or climatic events like increased storminess, require an understanding of how specific segments of the coastline have responded over millennial time-scales. This longer-term evolution provides the baseline information for decision making and management strategy. It is likely that sandy sediment supply is limited on the NNC and this implies that the barriers will continue to move landward, probably at increased rates relative to today, suggesting that parts of the NNC will become more vulnerable to erosion and flooding.

Investigating the carbon isotope composition and leaf wax n-alkane concentration of C3 and C4 plants in Stiffkey saltmarsh, Norfolk, UK

“…Spring tides can be in excess of 5 m, and storm surges from the North Sea can occur (Callaway et al, 1998;Andrews et al, 2000).…”

Instant luminescence chronologies? High resolution luminescence profiles using a portable luminescence reader

“…North Norfolk has a low-lying coast with a moderate to low wave regime from the north-east, a westerly longshore drift and macro-meso tidal ranges (Andrews et al 2000). Its wide sandy beaches and/or subtidal sand flats have given rise to extensive coastal dunes that form multiple coast parallel barriers up to 10 m high.…”

“…Its wide sandy beaches and/or subtidal sand flats have given rise to extensive coastal dunes that form multiple coast parallel barriers up to 10 m high. The coast at Holkham is known to have been prograding during the Holocene (Andrews et al 2000). Historic maps (1 st series ordnance survey) and aerial imagery (Crown copyright Royal Air Force aerial photographs 1946, Norfolk County Council aerial survey 1988 and Get Mapping imagery 2007 via Google Earth) show the coast to have continues to prograde and the back beach dunes are still actively accumulating sediment today.…”

Sedimentary records of coastal storm surges: Evidence of the 1953 North Sea event

“…This coastline is low-lying and characterised by a moderate to low wave regime from the North Sea, westerly longshore drift and macro-meso tidal ranges (Andrews et al, 2000;Bateman et al, 2015). The coast at Holkham prograded during the Holocene and there is active accumulation of beach dunes at present (Andrews et al, 2000;Bateman et al, 2018). We shingle and sand on salt marshes at this location (Steers, 1953;Spencer et al, 2015).…”