Jade Yesim Unal HBSc thesis abstract

The diagenetic history of a Carboniferous limestone sheet (Ardness Formation) present in the Cumberland Basin, Nova Scotia, was studied.

The diagenetic environments that altered the limestones of the study area were:  1) Near-Surface Processes  2) Vadose Processes, which only affected Knoydart Brook oolitic shoals  3) Freshwater Phreatic Processes  4) Deep Burial Processes  5) Hydrothermal Processes.

Petrographic evidence suggested the following sequence of diagenetic events:  1) bioturbation as a form of biological diagenesis in Knoydart Brook but not in Northumberland Shore,  2) microboring and the consequent micritization of bioclasts forming micrite envelopes,  3) early compaction,  4) very early freshwater-phreatic cements around echinoderm plates in the form of syntaxial overgrowth cement, and around ooids in the form of drusy cement,  5) grain-to-grain pressure solution,  6) blocky cement as well as void filling calcite cement.

Other processes which were pervasive throughout the sections are  7) neomorphism,  8) stylolite formation,  9) pyrite and hydrocarbon overprints.

The cements in the study area were mostly Mn-enriched and are likely to have precipitated from Mn-rich fluids that were related to hydrothermal vein systems.  Mn content in some ooids is higher than nearby cement indicating that the ooids were formed from Mn-rich seawater.  The hydrothermal processes were most affective near the basin margin of the shallow Windsorian area, a continental setting similar to the present day Persian Gulf.  In this case a hydrothermal vein system was operative near the continental transform faults of the Cumberland Basin during an early stage of block movement.  Hydrothermal fluids which were generated by convection within the basin rose along the permeable zones and fractures of the basin margin faults and carried Mn and other base metals towards the surface.