Geology of the Codroy Valley, Southwestern Newfoundland, including results of a preliminary palynological investigation

Utting, John (1966) Geology of the Codroy Valley, Southwestern Newfoundland, including results of a preliminary palynological investigation. Masters thesis, Memorial University of Newfoundland.

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Abstract

A detailed field mapping programme and palaeontological study of Codroy Valley area, southwestern Newfoundland, has yielded evidence that the boundary between the Codroy Group (Mississippian) and the Searston beds-Barachois Group (Upper Mississippian and Pennsylvanian), as mapped by earlier workers, required emendation. -- A general lack of diagnostic macrofossils in critical areas has been commented on by previous workers, and microfossils have been listed only in a few cases, but little work appears to have been done in this field. Rock samples were collected from the map area and later investigated in the laboratory for microfossils. Eighty eight rock samples were macerated for spores and good diagnostic assemblages were found in six of these. Productive samples were found in the Codroy Group, Searston beds and the Barachois Group, comprising a total spore florule of fifteen genera. These included Convolutispora, Lophotriletes, Lycospora, Reticulatisporites and Verrucosisporites from the Codroy Group; Convolutispora, Lycospora, Perotrilites and Raistrickia from the Searston Beds; and Calamospora, Cirratriradites, Densosporites, Florinites, Granulatisporites, Knoxisporites, Leiotriletes, Lophotriletes, Savitrisporites nux and Schopfipollenites from the Barachois Group. -- Five previously unrecorded localities containing ostracods were found and specimens of Glyptopleura sagae? and Paraparchites sp. were identified. A number of new macrofossil localities were also discovered comprising a total assemblage of 15 genera and 17 species. Vertebrate skeletal remains and fossil trackways of tetrapods were found in rocks of the Codroy Group. -- Structural studies revealed four general fault trends in the Codroy Valley area. A detailed sedimentary investigation was made of a coastal portion of the Searston bed sequence. Here, more than 70 diastems were counted separating cyclothems made up of conglomerate-sandstone units and lutite units. The depositional environment in which they were laid down appears to have been one of fluviatile sedimentation under warm humid climatic coiKiitions. -- Five lithostratigraphic types - coal, limestone, arkosic sediments, a boulder (conglomerate) bed, bedded chert - were investigated with a view to establishing marker or key beds in the Searston beds-Barachois Group. The first four types proved inadequate for the role of marker beds. Evidence is given for the continuity of a chert bed permitting it to be used for a key bed. The boundary between the Searston beds and the underlying Codroy Group is arbitrarily chosen at the base of this chert bed.

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