Litho- and Biostratigraphic analysis of the Upper Cretaceous Carlile and Niobrara formations in southern Saskatchewan, Canada

The Carlile and Niobrara formations were deposited during the regressive phase of the Greenhorn cycle and the transgressive phase of the Niobrara cycle (early Turonian-late Santonian). The lateral distribution of these units was controlled by eustatic sea level changes and differential accommodation space generated by dynamic and flexural subsidence of the Western Interior Basin (WIB). Analyses of these two units and stratigraphic equivalents within the Canadian portion of the WIB have been made mainly in the neighboring provinces of Alberta and Manitoba, but little is known about them in Saskatchewan. To fulfill the litho- and biostratigraphic gap of information in this area, lithological descriptions, and micropaleontological analyses were made in six cores along the southernmost portion of the basin (between Townships 13 and 24). Foraminifera have been used in this study not only as biostratigraphic markers but also as tools for the reconstruction of oceanographic conditions during the Turonian-Santonian. The lithostratigraphic framework adopted in this study indicates that in southwestern Saskatchewan, the Carlile Formation is subdivided into three informal subunits whereas the Niobrara Formation is subdivided into the Govenlock, Medicine Hat, and First White Specks members, as previous studies have suggested. In south-central Saskatchewan, only a three meters unconformity-bounded interval of the Carlile Formation (Morden Member) was identified. This model also indicates that the Morden Member in southeastern Saskatchewan is a condensed stratigraphic equivalent of the lower and middle Carlile subunits of the west, whereas the slightly calcareous Boyne Member in the same area is a stratigraphic equivalent of the upper Carlile subunit. The Niobrara Formation in south-central and southeastern Saskatchewan is subdivided into the lower Calcareous Shale Member and the upper First White Specks Member. Seven foraminiferal zones and three subzones were recognized in the Carlile and Niobrara formations, the uppermost part of the Second White Specks Formation and the lowermost part of the Milk River Formation. The Whiteinella aprica Subzone (Muricohedbergella loetterlei Zone) represents the transgressive phase of the Greenhorn Cycle occurred during the early Turonian. This maximum transgression was followed by a major environmental shift as a result of increased tectonic activity and a drop in eustatic sea level. During this time, agglutinated foraminiferal species of the Pseudoclavulina sp. Zone dwelled at the sea floor mainly in southwestern Saskatchewan and were subsequently replaced by calcareous benthic and planktic species of the Gavelinella kansasensis Subzone (Trochammina sp. Zone). The initial stage of the transgressive Niobrara Cycle (early Coniacian) is characterized by increased volcanic activity, the disappearance of foraminifera and the first occurrence of radiolarians at the base of the Govenlock Member of the Niobrara Formation. After the volcanic event, foraminifera of the Marsonella oxycona Subzone recolonized the sea floor followed by the highly diverse Bullopora laevis microfauna. The late stage of the transgressive Niobrara Cycle is represented by the benthic-dominated Gavelinella henbesti Zone and the planktic-dominated “Heterohelix cf. reussi” Zone.

Name thesis:degree_name

Master of Science (MSc)

Level thesis:degree_level

Master's

Discipline thesis:degree_discipline

Geology

Grantor dc:publisher

Faculty of Graduate Studies and Research, University of Regina

Year dc:date.issued

2017

Author dc:creator

• Diaz Tamayo, Juan Fernando

Advisor dc:contributor.advisor

• Velez Caicedo, Maria

Committee member dc:contributor.committeemember

• Bend, Stephen

Language dc:language.iso

en

DOI

https://doi.org/10.82465/4729

OAI identifier oai:identifier

oai:uregina.scholaris.ca:10294/7710