B.A.S.S. DIVISION
Upcoming Division Talk

Coeval deposition and the implications for sequence stratigraphic correlations in a structurally controlled area of the Viking Formation

SPEAKER: Sarah K. Schultz | Alberta Geological Survey

Co-authors: James A. MacEachern and Shahin E. Dashtgard | Simon Fraser University; Octavian Catuneanu | University of Alberta
LOCATION: geoLOGIC Room (2nd Floor), Aquitaine Tower, 540-5th Avenue S.W., Calgary
DATE & TIME: 12:00 Noon Wednesday, October 30th, 2019


*CSPG members can register for free and track their CPD hours!

ABSTRACT
The late Albian Viking Formation is a stratigraphically complex unit that exhibits significant along-strike variability of paleoshorelines that developed in response to autogenic processes as well as allogenic controls that were active during deposition. Structural reactivation of Precambrian basement structures occurred during Viking deposition and led to changes in depositional environments along the paleoshoreline. This tectonic activity influenced sedimentation patterns and the creation of anomalous zones of accommodation in localized areas of the basin. Across fault boundaries, both progradational and retrogradational stacking patterns occur within broadly contemporaneous deposits, complicating the correlation of stratigraphic units. These local structural controls that influenced deposition must be incorporated into the working sequence stratigraphic model.

Variability in accommodation and sedimentation rates within a basin generates significant deviations in the along-strike stratal stacking patterns of systems tracts. This variability can lead to coeval depositional units that record juxtaposition of transgressive (retrogradational) and regressive (progradational) stratal stacking patterns. In instances where transgressive and regressive units are deposited concurrently, problems arise when attempting to correlate the systems tracts and place their accompanying deposits into a sequence stratigraphic framework. In order to accurately incorporate these complex areas into a developing framework, a data-driven approach that integrates both allogenic and autogenic controls must be utilized when modelling the 3D architectural variability of subsurface units.

Few studies have documented the effect(s) of structural control on systems tract development. Coeval deposition of regressive and transgressive units can occur in multiple environmental settings including: i) tectonically active fault zones (leading to differential subsidence); ii) depositional environments wherein sedimentation rates may vary significantly along strike (e.g., deltas); and iii) areas where both sedimentation and accommodation rates are variable (Catuneanu, 2019). Under any combination of these depositional settings, conditions may operate wherein progradational and retrogradational stacking patterns are generated concurrently, leading to challenges when extending correlations at a basin-scale.
Coeval deposition of transgressive and regressive units is likely more common than has been documented in the literature to date. Modern marginal-marine examples highlight how variabilities in accommodation and sedimentation rates play a pronounced role in the development of shoreline architecture. Coeval deposition has likely occurred in other formations in the Western Canadian Sedimentary Basin, and it is therefore crucial to integrate this concept into future stratigraphic models in order to generate high-resolution datasets even in well-explored areas of the basin.

BIOGRAPHY
Sarah is in the final year of her PhD studies at Simon Fraser University. The results of her PhD on the Viking Formation have been presented at 8 conferences, including 4 core conferences and a CSPG BASS Luncheon in 2017.
Sarah currently works for the Alberta Geological Survey and is focusing on resolving the stratigraphic architecture of Paleozoic successions throughout Alberta.


The Sunset Prairie Formation: Insight on the Complexity of the Montney-Doig Boundary through the Integration of Sedimentology, Ichnology and Sequence Stratigraphy

SPEAKER: Carolyn Furlong | University of Alberta

LOCATION: geoLOGIC Room (2nd Floor), Aquitaine Tower, 540-5th Avenue S.W., Calgary
DATE & TIME: 12:00 Noon Wednesday, November 5th, 2019


*CSPG members can register for free and track their CPD hours!

ABSTRACT
The Sunset Prairie Formation is a newly named Middle Triassic formation in the Western Canada Sedimentary Basin and is found mainly in northeastern British Columbia (Furlong et al., 2018a). Sitting above the Montney Formation (one of Canada's most important unconventional reservoir intervals), the Sunset Prairie Formation has the potential to contribute valuable hydrocarbon resources to wells drilled into Triassic horizons. This study incorporates sedimentological and ichnological characteristics of the Sunset Prairie Formation to construct a sequence stratigraphic framework to understand depositional dynamics and basin evolution. All of this is useful for evaluating and predicting reservoir distribution and exploration potential of the Sunset Prairie Formation.

The Sunset Prairie Formation is lithologically, ichnologically and paleontologically distinct from underlying and overlying strata. The formation consists of interbedded light gray, pervasively bioturbated sandstone and dark gray, diminutively bioturbated to non-bioturbated siltstone. Trace fossils within the unit include Asterosoma, Chondrites, Cylindrichnus, Diplocraterion, Helminthopsis, Palaeophycus, Phycosiphon, Planolites, Rhizocorallium, Rosselia, Scolicia, Skolithos, Teichichnus, Thalassinoides and Zoophycos. Paleontological assemblages include bivalves, gastropods, lingulid brachiopods (which all occur within the Montney and Doig Formations), and spiriferid brachiopods, terebratulid brachiopods, echinoderm spines and crinoid ossicles (which are quintessential components of the Middle Triassic fauna).
Collectively, seven facies were identified and are ascribed to offshore, offshore transition and lower shoreface depositional facies associations (Furlong et al., 2018b). Three shoaling-upward parasequences can be identified through upward increases in grain size (up to very fine-grained sandstone), bioturbation intensity and trace fossil size. Additionally, a Glossifungites-demarcated discontinuity surface and/or conglomeratic lag deposit is observed at the base of each parasequence. The retrogradational stacking pattern of parasequences suggests an increase in relative sea level during deposition. The formation is bound by unconformities. The lower unconformity truncates the underlying Montney Formation. The upper unconformity, at the base of the Doig phosphate zone, truncates the Sunset Prairie Formation and, to the east, incises into the Montney Formation. Two sequence stratigraphic frameworks are proposed for the Sunset Prairie Formation. The first interprets the formation to represent lowstand systems tract during deposition of the lowermost parasequence, which is capped by a maximum regressive surface; the overlying two parasequences represent the transgressive systems tract. The second model interprets the entire formation to represent a transgressive systems tract. Each model has strengths and flaws associated with its interpretation. 

Regardless of which model is favoured, the retrogradational nature of the parasequences cause the lowermost parasequence to exhibit the thickest packages (up to 7 meters) of pervasively bioturbated, very-fine grained sandstone. Fine-grained sand content, thickness of coarse-grained beds and bioturbation intensity decrease with each proceeding parasequence. The result of this retrograde stacking pattern and high net to gross sand in the lowermost parasequence produces a “pseudo conventional” reservoir within a dominantly tight sandstone/siltstone interval. Elucidating the sequence stratigraphic architecture allows for better prediction of potential reservoir intervals to optimize hydrocarbon recovery within the Sunset Prairie Formation.

References
Furlong, C.M., Gingras, M.K., Moslow, T. and Zonneveld, J-P. 2018a. The Sunset Prairie Formation: Designation of a new Middle Triassic formation between the Lower Triassic Montney Formation and Middle Triassic Doig Formation in the Western Canada Sedimentary Basin. Bulletin of Canadian Petroleum Geology, v. 66, p. 193-214.
Furlong, C.M., Gegolick, A., Gingras, M.K., Hernandez, P., Moslow, T., Prenoslo, D, Playter, T. and Zonneveld, J-P. 2018b. Sedimentology and Ichnology of the Middle Triassic (Anisian) Sunset Prairie Formation of the Western Canada Sedimentary Basin. Bulletin of Canadian Petroleum Geology, v. 66, p. 215-236.

BIOGRAPHY
Carolyn Furlong recently received her PhD in geology from the University of Alberta. Her thesis focused on naming and describing the Sunset Prairie Formation. Her previous research has focused on understanding the interplay between geology and biology within both modern and ancient settings. Carolyn holds a B.Sc. in earth science education from the State University of New York College at Cortland and a M.Sc. in geology from the University of Alberta. 

Division Profile

Our meeting schedule is to have at least one informal brown-bag talk every month, except during the summer. Talks normally start at 12:00 noon and finish before 1:00 p.m. Each talk consists of a 40 minute technical presentation followed by a 10 minute question period. 

Involvement of our CSPG members is the key to the success of the Division. Individuals are encouraged to take part in all activities. Service companies are also encouraged to attend Division meetings and be involved in all Division activities. Basin Analysis and Sequence Stratigraphy Technical Division Talks are free to CSPG members. Please bring your lunch. For further information about the division, joining our mailing list, a list of upcoming talks, or if you wish to present a talk or lead a field trip, please contact either Steve Donaldson at (403) 808-8641 or Mark Caplan at (403) 975-7701.

Committee Members
Co-Chair: Steve Donaldson 
Co-Chair: Mark Caplan
Committee members: 
Dragos Distaru
Rob North
Russ Phillips
Richard Wong
     Division Sponsor         Refreshment Sponsor            Venue Sponsor
                              

Past Presentations

January 16th, 2019
Western Canada Sedimentary Basin Petroleum Systems: A Working and Evolving Paradigm - Kirk Osadetz
Download Slides (.PDF)
April 27th, 2016
Sequence Stratigraphic Analysis of Mixed, Reefal Carbonate and Siliciclastic Systems - Ashton Embry
Download Slides (.PDF)
March 11th, 2015
Geological Risk - Kirk Osadetz
Download Slides (.PDF)
March 14th, 2014
The Future of Gas Hyrdates as a Fuel - Kirk Osadetz 
Download Slides (.PDF)
February 11th, 2014
Alberta Hydrocarbon - Bearing Shales & Siltstones - Steve Lyster & Dean Rokosh
Download Slides (.PDF)