Sedimentology and depositional history of the Chapel Island Formation (late Precambrian to early Cambrian), southeast Newfoundland
The Chapel Island Formation, a 1000 m thick shelf sequence of late Precambrian-Early Cambrian age, is receiving considerable attention as a leading candidate for the boundary stratotype for the Precambrian-Cambrian boundary. The formation, composed of five informally defined members, has been divide...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
1987
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| Online Access: | https://research.library.mun.ca/6779/ https://research.library.mun.ca/6779/1/PaulMichaelMyrow.pdf https://research.library.mun.ca/6779/3/PaulMichaelMyrow.pdf |
| Summary: | The Chapel Island Formation, a 1000 m thick shelf sequence of late Precambrian-Early Cambrian age, is receiving considerable attention as a leading candidate for the boundary stratotype for the Precambrian-Cambrian boundary. The formation, composed of five informally defined members, has been divided into six facies associations (1-6). -- Facies Association 1 consists of red and green sandstones and shales (Facies 1.1/1.2), and grey to black, thinly laminated shales and silty shales (Facies 1.3), deposited in tidally-influenced peritidal and semi-restricted shoreline environments, respectively. -- Facies Association 2 consists of very thin to medium bedded sandstones and siltstones (Facies 2.1/2.2) with subordinate green and red laminated siltstones (Facies 2.3/2/4), deposited within a muddy deltaic system. Storm-generated sandstones (tempestites), and other storm-related features (e.g., gutter and pot casts), dominate Facies 2.1 and 2.2. These facies are also characterized by abundant and diverse slide and gravity-flow features (debrites, turbidites, and liquefied flow deposits) formed under conditions of high sediment supply in a delta front/upper prodelta setting. Thin bedded and laminated siltstones of Facies 2.3/2.4 form excellent marker horizons and represent delta abandonment facies. -- Laminated green siltstones of Facies Association 3 are considered outer shelf deposits. Sandstone laminae are interpreted as distal tempestites deposited by waning flows below storm wave base. -- Facies Association 4 consists of red, green and gray mudstones of inner shelf origin and thing fossiliferous algal limestones deposited in peritidal environments. Deposition took place on a low energy, oxygen-stratified muddy shelf, with the limestone beds forming during low stands of sea level. -- Facies Associations 5 and 6 were deposited on a storm- and wave-dominated shelf below and above the influence of storm waves, respectively. The thin to medium bedded sandstones and siltstones of Facies Association 5 represent distal ... |
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