Karst development in Ordovician carbonates: Western Platform of Newfoundland

Abstract

<p>The Appalachian fold belt system in Newfoundland is divided into three tectonic divisions: Western Platform; Central Mobile Belt; Avalon Platform Rocks of the Western Platform range in age from Precambrian to Carboniferous. Major karst areas are found there is Ordovician and Carboniferous rocks. Karst features of the study area (Goose Arm to Bonne Bay Big Pond) are in the Ordovician carbonates of the undivided St. George and Table Head Formations, covering a few hundred square kilometers. Features include karren, sinkholes, sinking streams, and karst springs, caves and other solutional and collapse features.</p> <p>In the study area multiple fold and faulting episodes complicate the geology. Extensive and probably repeated glaciations have produced rugged terrane with U-shaped valleys and as much as 300m relief on the carbonates. There is variable but thick till cover. A class or classes of ice-scoured closed depressions with internal drainage are recognized. Postglacial karst forms are limited to varieties of karren (mainly littoral), small sinkholes, and cave systems that are inaccessively small in most instances. Distribution of all karst features is highly irregular.</p> <p>Hydrologic patterns follow fluvial, fluviokarstic and holokarstic drainage. Large number of sinking ponds have seasonal overflow channels. The ground water drainage routes are generally short and shallow, with varied hydraulic gradients. Few instances of ground water route integration to regional springs is found.</p> <p>The water chemistry of the area displays a tight normal distribution of hardness. This is attributed to the ponding effect. Seasonal trends show an overall increase in total hardness and other parameters, with some ponds showing linear increases and others cyclic variations.</p> <p>Karst type and distribution is complex and irregular, but both glaciokarstic and karstiglacial development is present. The majority of karst forms point to karstiglacial development where previous karst forms have been modified by ice. Karstification is controlled by geology, rock lithology, hydraulic gradients and glacial scour and infill. Karstic processes continue to operate today, modifying the scoured basins and creating new karst forms.</p>