Abstract
Summary Middle Old Red Sandstone lacustrine sequences in the Orcadian Basin include rocks of petroleum source-rock potential, most extensively exposed onshore in Orkney and Caithness. The richest source rocks are carbonate laminites, in which carbonate and carbonaceous laminae are believed to be the deposits of algal blooming and mortality in a stratified lake (Donovan 1980). Many carbonate laminites and some other organic-rich laminites contain chert nodules, interpreted as magadi-type chert enclosing pseudomorphs after (?) trona. The cherts and evaporites were precipitated in sub-lacustrine sediment from groundwaters rich in dissolved sodium carbonate/bicarbonate. This implies that the source rocks were deposited from saline, alkaline lake waters.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
