N. Bingham-Koslowski, M. Miller, T. McCartney, J. Carey
{"title":"Revised biostratigraphic and thermal alteration interpretations for the Paleozoic of the Hopedale Basin, offshore Labrador, Canada","authors":"N. Bingham-Koslowski, M. Miller, T. McCartney, J. Carey","doi":"10.35767/gscpgbull.67.3.185","DOIUrl":null,"url":null,"abstract":"\n Paleozoic rocks occur in seven wells in the Hopedale Basin, offshore Labrador (Hopedale E-33, South Hopedale L-39, Tyrk P-100, Gudrid H-55, Roberval K-92, Indian Harbour M-52, and Freydis B-87), where they represent erosional remnants primarily associated with Cretaceous syn-rift half grabens. Previous palynological studies have reported a range of ages for the Paleozoic in these wells, including Ordovician, Devonian, Carboniferous, and undifferentiated Paleozoic. Palynological analyses in the present study confirm that recovery is limited, primarily due to the predominance of lithologies that hinder palynomorph preservation, specifically dolostones. Palynomorphs (predominantly acritarchs and chitinozoans) have been analyzed from new and archived samples from the seven wells and have, for the first time, produced consistent age determinations for the Paleozoic strata in all wells: palynomorph assemblages considered in place indicate a Middle to Late Ordovician age. Thermal maturity was determined from Ordovician acritarchs and leiospheres observed in the Gudrid H-55, Roberval K-92, Indian Harbour M-52, and Freydis B-87 wells, with thermal alteration indices (TAI) ranging from approximately 5+ to 6+ (dry gas). Carboniferous miospores are present from Paleozoic strata in the southern Hopedale Basin wells, where their TAI values range from 3+ to 4. These miospores are interpreted as contaminants introduced into the samples via cavings or as drilling mud contamination. The data presented here provides new biostratigraphic constraints for the Paleozoic of the Hopedale Basin (Middle to Late Ordovician), facilitates the correlation of the Paleozoic intervals in these wells, and enables the consideration of Labrador margin Lower Paleozoic strata in regional studies as well as in paleogeographic and paleoenvironmental reconstructions.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":" ","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2019-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bullentin of Canadian Petroleum Geology","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.35767/gscpgbull.67.3.185","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Earth and Planetary Sciences","Score":null,"Total":0}
引用次数: 1
Abstract
Paleozoic rocks occur in seven wells in the Hopedale Basin, offshore Labrador (Hopedale E-33, South Hopedale L-39, Tyrk P-100, Gudrid H-55, Roberval K-92, Indian Harbour M-52, and Freydis B-87), where they represent erosional remnants primarily associated with Cretaceous syn-rift half grabens. Previous palynological studies have reported a range of ages for the Paleozoic in these wells, including Ordovician, Devonian, Carboniferous, and undifferentiated Paleozoic. Palynological analyses in the present study confirm that recovery is limited, primarily due to the predominance of lithologies that hinder palynomorph preservation, specifically dolostones. Palynomorphs (predominantly acritarchs and chitinozoans) have been analyzed from new and archived samples from the seven wells and have, for the first time, produced consistent age determinations for the Paleozoic strata in all wells: palynomorph assemblages considered in place indicate a Middle to Late Ordovician age. Thermal maturity was determined from Ordovician acritarchs and leiospheres observed in the Gudrid H-55, Roberval K-92, Indian Harbour M-52, and Freydis B-87 wells, with thermal alteration indices (TAI) ranging from approximately 5+ to 6+ (dry gas). Carboniferous miospores are present from Paleozoic strata in the southern Hopedale Basin wells, where their TAI values range from 3+ to 4. These miospores are interpreted as contaminants introduced into the samples via cavings or as drilling mud contamination. The data presented here provides new biostratigraphic constraints for the Paleozoic of the Hopedale Basin (Middle to Late Ordovician), facilitates the correlation of the Paleozoic intervals in these wells, and enables the consideration of Labrador margin Lower Paleozoic strata in regional studies as well as in paleogeographic and paleoenvironmental reconstructions.
期刊介绍:
The Bulletin of Canadian Petroleum Geology is a peer-reviewed scientific journal published four times a year. Founded in 1953, the BCPG aims to be the journal of record for papers dealing with all aspects of petroleum geology, broadly conceived, with a particularly (though not exclusively) Canadian focus. International submissions are encouraged, especially where a connection can be made to Canadian examples.