Conodonts and phosphatic problematica from the Cambro-Ordovician Cooks Brook and Middle Arm Point formations, Bay of Islands, western Newfoundland

• Main Author: Roy, Kaustuv
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1989
• Subjects: Middle Arm; Arm Point; Middle Arm Point; Newfoundland
• Online Access: https://research.library.mun.ca/4289/; https://research.library.mun.ca/4289/1/Roy_Kaustuv.pdf; https://research.library.mun.ca/4289/3/Roy_Kaustuv.pdf

The Cooks Brook and Middle Arm Point formations, situated in Bay of Islands, western Newfoundland mainly consist of deep-water carbonates and shales ranging in age from middle Cambrian to early Ordovician. Previous studies have shown that these rocks were deposited as a "base-of-slope sediment apron", downslope from a carbonate platform. -- A total of 143 samples from five sections spanning the Cooks Brook and Middle Arm Point formations were collected for conodonts and other microfossils. Of these, 38 samples yielded identifiable conodonts and 19 samples yielded various types of phosphatic problematica. Systematic study of the conodonts have resulted in the identification of 68 species which are assignable to 36 genera. Three new unnamed genera have been described. -- The conodont fauna permits the recognition of six standard uppermost Cambrian-lowermost Ordovician conodont zones within the Cooks Brook Formation. These zones are: (i) Proconodontus tenuiserratus Zone, (ii) Proconodontus muelleri Zone, (iii) Eoconodontus Zone, (iv) Cordylodus proavus Zone, (v) Cordylodus angulatus Zone and the (vi) Loxodus bransoni Interval. -- The conodonts from the lower part of the Middle Arm Point Formation are assigned to Fauna D of Ethington and Clark (1971) while conodonts from the uppermost Middle Arm Point Formation are assigned to the Prioniodus elegans Zone. -- Based on the conodont fauna the age of middle and upper Cooks Brook Formation ranges from uppermost Franconian to middle(?) Tremadocian. The Middle Arm Point Formation, on the other hand, ranges in age from middle(?) Tremadocian to lower Arenigian. Within the Cooks Brook Formation, the Cambro-Ordovician Boundary can be placed either at the base of the Cordylodus proavus Zone or at the base of the Cordylodus angulatus Zone. -- The abundance and distribution of conodonts within the Cooks Brook and Middle Arm Point formations show strong environmental control and suggest that most of these conodonts were benthic or nektobenthic in habit. -- The phosphatic ...