Congratulations to Harold Kuehn for the successful defense of his PhD thesis entitled “Along-trench segmentation and downdip limit of the seismogenic zone at the eastern Alaska-Aleutian subduction zone“. His examining committee were all uniformly impressed by the quality of his work! Congrats also to his supervisor Mladen Nedimovic.
B.Sc. Honours (Earth Science), McGill University, 2005
M.Sc. (Geology), University of New Brunswick, 2008
DEPARTMENT OF EARTH SCIENCE
THE GENESIS AND EVOLUTION OF
MAKAROV BASIN, ARCTIC OCEAN
9:30a.m., Tuesday, April 24, 2018
Room 3107, The Mona Campbell Building
1459 LeMarchant Street
Dr. Carmen Gaina, Centre for Earth Evolution and Dynamics, University of Oslo (External Examiner)
Dr. Keith Louden, Department of Oceanography, Dalhousie University (Reader)
Dr. Gordon Oakey, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography (Reader)
Dr. John Gosse, Department of Earth Science, Dalhousie University (CoSupervisor)
Dr. David Mosher, Adjunct, Department Earth Sciences, Dalhousie University and Geological Survey of Canada- Atlantic, Natural Resources Canada, Bedford Institute of Oceanography (Co-Supervisor)
Dr. James Brenan, Department of Earth Science, Dalhousie University
Jure Gantar, PhD Defence Panel, Faculty of Graduate Studies
Plate tectonic theory commenced with the observation that continental margins fit together like pieces of a puzzle. No such fit is readily apparent to the margins of Amerasia Basin of the Arctic Ocean, resulting in a stubborn outlier to global plate-reconstructions. This problem persists partly because of a paucity of data in the perennial ice-covered seas. Makarov
Basin is well-positioned to address this problem, situated at the northern margin of Amerasia Basin, adjacent to Lomonosov Ridge. This study tests the hypothesis that this segment is a transform margin that resulted from rotational opening of Amerasia Basin. For this purpose, this study analyses the seismic stratigraphy, geomorphology, potential field and seismic
velocity data of Makarov Basin and surrounding areas. The data are mainly from a unique seismic line that transects Makarov Basin and onto Lomonosov Ridge.
The sedimentary cover averages 1.9 km-thick in Makarov Basin, with a maximum thickness of – 5 km in a northern deep subbasin. The deeper successions within the subbasin host interbedded volcanic and/or volcaniclastic material. A shift in sedimentary supply, from proximal to distal, is recorded after the onset of Cenozoic rifting that separated Lomonosov Ridge from the Barents-Kara Shelf and formed Eurasia Basin. Thereafter, sedimentation is largely pelagic to hemipelagic.
The crust of Makarov Basin is typically 9 to 11 km thick, except beneaththe subbasin where it is 5 km thick. The crust abruptly thickens to >20 km from Makarov Basin to central Lomonosov Ridgb. Results from gravity modelling reveal that the tectonic style of the Amerasian margin of Lomonosov Ridge varies from passive rifting to strike-slip along its length. The rhomboid shape of Makarov Basin, the straight and steep morphology of the Amerasian flank of Lomonosov Ridge, the presence of numerous sub-parallel ridges created by splay faulting and the abrupt crustal transition between the two provinces is evidence of transverse/transtensional tectonics along the central segment of the ridge. This result supports a rotational model of opening for Amerasia Basin, at least for its initial stages, and is a critical element to understanding the larger tectonic framework of the Arctic Ocean.
M.Sc. THESIS DEFENCE
DEPARTMENT OF EARTH SCIENCES
“SEISMIC STRATIGRAPHY AND ARCHITECTURE OF THE JURASSIC ABENAKI MARGIN,
AT COHASSET-MIGRANT, AND POTENTIAL FOR DISTAL ORGANIC-RICH FACIES”
PLACE: The Milligan Room, 8th Floor Biology Wing, LSC, Dalhousie University
DATE: Friday, April 20, 2018
TIME: 10:00 a.m.
Dr. Laurence Davis Husky Energy, Atlantic Region External Examiner
Dr. Mladen Nedimovic Dalhousie University Reader
Mr. David Brown Canada-N.S. Offshore Petroleum Board Reader
Dr. Grant Wach Dalhousie University Supervisor
Dr. John Gosse Dalhousie University Chair
PLEASE NOTE: A copy of the thesis is available in the main Earth Sciences Office
This study uses well data, extensive 3D seismic data and geologic analogs to test and extend stratigraphic concepts and models in a mixed clastic-carbonate depositional setting: the Middle Jurassic to Early Cretaceous of the Sable Sub-basin, offshore Nova Scotia. The study focuses on basinward mapping of third-order depositional sequences identified in the Abenaki carbonate bank at Deep Panuke Field and addresses: source rock potential in coeval basinal calcareous mudstones; changes in bank margin morphology related to underlying basement; the transition from a dominantly carbonate system at the shelf margin to a fluvio-deltaic system, the Sable Delta, that extends to the Late Cretaceous; the presence of thick fluvio-deltaic sediments adjacent to basinal mudstones outboard of the carbonate bank.
These depositional systems are uniquely imaged by 3D seismic data in the area around the Cohasset L-97 and Migrant N-20 well penetrations. Core studies of wells which penetrated the Abenaki carbonate bank and field studies in the Lusitanian Basin, onshore Portugal, provide calibration and analogs to shallow water carbonates in the Cohasset area. Further ancient and modern analogs are discussed in Morocco and at the termination of the Great Barrier Reef in the Gulf of Papua.
Geological, petrophysical and geophysical interpretation methods are used to interpret the depositional cycles and stratigraphic framework of limestones and calcareous shales that were deposited in increasingly deeper water outboard of the Abenaki margin. This framework formed the basis for a 3D geocellular model that was populated with lithologies from well data via a seismic inversion. This model was interpreted in terms of environments of deposition and source rock potential.
The third-order sequence stratigraphic framework was modified from a framework established at Deep Panuke gas field where commercial production began in August 2013. This third-order chrono-stratigraphic framework (“Abenaki 1-7 surfaces”) incorporates multiple litho-stratigraphically defined formations: the Mohican, Mohawk, Mic Mac, Abenaki, Missisauga and Verrill Canyon formations. Thick fluvio-deltaic successions adjacent to basinal mudstones in the Migrant N-20 well are interpreted to be structurally controlled, deposited in local depocentres, that formed in response to sediment loading, listric faulting and mobile salt substrate.
Results from the study show that condensed sections of the distal carbonate depositional system in Abenaki 1-4 sequences have potential to host organic-rich material. The basinal shales of these sequences are estimated to have been deposited in up to approximately 200 m water depths and have type 2 source rock potential. A change in seismic signatures and facies occurs between Abenaki sequences 1-4 and Abenaki sequences 5-7 reflecting encroachment of the Sable Delta, and it is interpreted that the Abenaki 5-7 sequences have predominantly type 3 source potential, with some potential for a type 2 source in intervening calcareous mudstones.
Congratulations to Jennifer Frail-Gauthier on a very successful PhD defence yesterday, with External Examiner Dr. Gail Chmura.