Recent temperate carbonate deposits on the Continental Shelf north and west of Scotland : distribution, sedimentology and reserves

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 1983
Thesis identifier
  • T4688
Qualification Level
Qualification Name
Department, School or Faculty
  • Widespread shelly carbonate sands and gravels have been revealed by a reconnaissance of the seabed north and west of Scotland using IG5 samples and geophysical data supplemented by material from further shipboard work. The carbonates cover large areas of the platform around Orkney and Shetland, and are generally less than 1m thick., although possibly reaching 30m in sandwaves and sandbanks around Orkney. Further west the deposits are rarely over 1m thick, smaller, and more isolated, except on the large platform west of the Outer Hebrides. Coastal carbonates occur as extensive beaches and machairs, and in bays and channels close inshore. Petrographic analysis, radiocarbon dating and bedforms show that most of the material is post-glacial and a product of the modern sedimentary regime. Theoretical considerations of shelly carbonate sediment transport and bedform formation support this, indicating that such bioclastic debris is extremely mobile. The basic requirements for the. formation of these temperate carbonates are relatively strong currents and low terrigenous input. These are inter-related and linked to the major controlling factors, bathymetry and exposure to open sea. Thus-carbonate sediments often occur on bathymetric highs: platforms, shoals and knolls, where rocky substrates are often exposed, where there are high rates of both growth and removal of carbonate-secreting organisms, and where the debris is not diluted by non-carbonate. Estimates of the reserves of each deposit and the total mass of superficial carbonate indicate average accumulation and production rates on the shelf of at least 24 g/m2 /yr. Around Orkney local accumulation rates may reach 580 g/m2/yr and production rates 97 g/m2/yr. An order of magnitude less than for tropical carbonates, these rates are very similar to those of ancient temperate carbonates and thus the Scottish sediments are important modern analogues. The material has considerable potential for commercial extraction, particularly in the Orkney area.
Advisor / supervisor
  • Duff, Donald
  • Russell, Mike
  • Fannin, Nigel
  • Bowes, George
Resource Type