Lower Border Group (Tournaisian) stromatolites from the Northumberland basin

Abstract

Synopsis: Lower Border Group stromatolites contain detrital, micritic and calcareous algal filament laminae. Growth forms include domes, blisters, polygons, pillars, clubs, cusps, crinkles, bioherms and oncolites. Environments of growth are interpreted from comparisons with Recent stromatolites and from the evidence of associated carbonate lithofacies. Stromatolites in the Liddel Formation are often of intertidal origin and their outcrops mark the former northern shorelines of the Northumberland gulf sea. Seaward accretion of algal flats over shallow subtidal carbonate lithofacies gave rise to shoreline regressional sequences, now seen in vertical sections. Stromatolites in the Main Algal Formation are of shallow subtidal origin and accreted in central parts of the gulf sea.