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2018 Geological Survey of Canada (GSC) Atlantic Science Hour

Who: R. Andrew MacRae

Department of Geology, Saint Mary's University
Halifax, Nova Scotia

What: Palynology of the Triassic-Jurassic section in the Argo F-38 well, Orpheus Graben, Scotian Margin: A salty bio- and chemostratigraphic tale

The oldest part of the Scotian Basin formed during the rift phase of the nascent Atlantic Ocean. The rift fill is mainly clastic redbeds and salt deposited in harsh, arid or saline environments that exclude most biostratigraphically useful groups with the exception of terrestrial pollen and spores (palynology). The salt itself plays an essential role in basin history because much of the later sedimentation is affected by salt tectonics, yet understanding of salt stratigraphy and coeval units is quite limited. The near lack of conventional cores in the interval makes the contamination issues from cuttings samples a constant concern for biostratigraphy, and there are also few well penetrations. Despite these challenges, with careful well selection and sampling technique, biostratigraphy is possible. At the Argo F-38 well, over 800m of salt-bearing section is present in a succession relatively undisturbed by subsequent salt tectonics. Proceeding downhole from unambiguous Middle Jurassic (Bajocian), dinoflagellate-bearing strata of the Mohican Formation, a distinctive pollen and spore flora of probable Hettangian or younger age (Early Jurassic Echinitosporites cf. iliacoides Zone of Bujak and Williams 1977) occurs in the Iroquois Formation, just above the youngest salt in the succession. This assemblage is dominated (usually >90%) by species of the pollen Classopollis. Towards the base of the salt interval, a few distinctive spore tops and plausible basal occurrences of spores typical of the Triassic-Jurassic boundary interval occur, though the exact position of the base occurrences must be regarded carefully in cuttings samples. There is no sign of marine dinoflagellates through this interval, but rare acritarchs may represent in-place aquatic flora, or arguably Paleozoic reworking. At the very base of the succession, just above basement in redbeds of the Eurydice Formation, the occurrence of a solitary Patinosporites densus specimen implies passage into the Late Triassic.

Coincident bromine geochemistry from the salt unit shows a transition from low Br salt near the base (<60ppm) to higher concentrations more typical of marine conditions higher in the succession (>60ppm). This trend is consistent with observations by previous workers on the southern Grand Banks, where there is a succession from the lower Br Osprey Formation to the younger, higher-Br Argo Formation within the Triassic-Jurassic interval. Comparison of the Argo F-38 biostratigraphy to previously published work at the Glooscap C- 63 well implies the latter's salt-bearing succession below CAMP basalt is significantly older within the Late Triassic than the base of Argo F-38, also consistent with the occurrence of the low-Br Osprey Formation there. Such a "two salt" stratigraphic model has broader implications for basin configuration and paleoenvironments across the region during the rift and early drift phase Atlantic Ocean tectonics.

Although the number of wells penetrating this interval in stratigraphic context is limited, this study shows that a finer biostratigraphic subdivision of it is possible with careful biostratigraphic sampling in cooperation with geochemical techniques.

When: 10:30 am, Wednesday, October 31, 2018

Where: AGC Boardroom, 5th Floor Murray, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Kristopher L. Kendell

Canada-Nova Scotia Offshore Petroleum Board
Halifax, Nova Scotia

What: Anthropic impacts on coastal systems, submarine geohazards and continental margins evolution

Carboniferous strata of the Sydney Basin outcrop onshore Cape Breton Island and extend offshore beneath the Laurentian Channel and Burin Platform. The offshore portion of the basin, between Nova Scotia and Newfoundland, is the predominant focus of this study. Subsurface maps were generated using an extensive suite of 2D seismic surveys that vary significantly in vintage and quality across the basin. Exploration wells intersecting the seismic data are shallow and only provide calibration of the Late Carboniferous seismic stratigraphy for the western and nearshore regions. To enhance interpretation of these variable quality surveys with limited well control, additional data sets were integrated into the workstation environment; including modern topography, surface geology, gravity, magnetics and research seismic.

Many of the seismic surveys were collected in the 1980's or earlier and imaging artefacts such as conventional seafloor and peg-leg multiples present a significant interpretation challenge. A recent seismic survey collected on the eastern side of the basin has substantially improved imaging, providing a higher degree of interpretation confidence that was used to guide interpretation on neighbouring poorer-quality surveys. In some areas, shallow, high-resolution research seismic profiles were vectorized and incorporated into the database. These shallow penetrating profiles helped to clearly distinguish higher amplitude flat-lying artefacts on the industry profiles, from folded dipping, and erosionally truncated Carboniferous and/or Permian strata. Significant efforts were also made to ensure that the shallow offshore geological interpretations were consistent with the stratigraphy exposed on Cape Breton Island. Likewise, exposed basement terranes in onshore areas were correlated with a moderate degree of confidence into offshore areas, with interpretations bolstered by the integrated gravity and magnetics data sets.

The integration and analysis of multiple data sets has reduced the many uncertainties that impeded an accurate subsurface interpretation of the Sydney Basin. Despite the remaining uncertainties, two significant observations can be made. (1) Pre-Carboniferous basement rocks are conceivably much shallower in the northern extent of the basin, consequently the overlying Carboniferous section thins to less than 1 km in some areas. (2) Horton Group rocks, and to a lesser degree the Windsor Group, may be localised and restricted to narrow grabens in the central Sydney Basin, thus occupying a less extensive area than previously interpreted.

When: 10:30 am, Wednesday, October 24, 2018

Where: AGC Boardroom, 5th Floor Murray, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Dr. Thomas James

GSC-Pacific (Sidney)

What: Projected Sea-Level Rise in Canada

Recent scientific findings on projected global sea-level rise, especially those related to stability of the Antarctic ice sheet, will be discussed in the context of recent work on updating relative sea-level projections for Canada.

When: 11:00 am, Wednesday, October 18, 2018

Where: AGC Boardroom, 5th Floor Murray, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Vittorio Maselli

School of Geosciences
University of Aberdeen

What: Anthropic impacts on coastal systems, submarine geohazards and continental margins evolution

This talk is aimed to present a brief overview of my experience in three particular research subjects and its potential application to the study of the Eastern Canada margin, in the light of my future position at the Department of Earth Sciences at Dalhousie University.

In the first part, I concentrate on coastal environments, probably the most complex, fragile and densely populated landscapes on Earth. Focusing on the largest southern European deltas, I will show how enhanced, and unaware, anthropic pressures on the landscape controlled their formation and retreat during the last few thousands of years. In the second part, I will outline research results associated with the study of marine geohazards, in particular tsunamis and landslides. I will present the results of a series of field campaigns along the coastline of Tanzania and the discovery of a 1000-yr old event that appears to have devastated a Swahili settlement. Tsunamis can be generated by earthquakes or by large submarine landslides, and it is often difficult to disentangle the role of different processes in promoting continental margin instability. Here, I will show how sediment supply, halokinesis and deep ocean circulation promoted margin instability along the Sigsbee Escarpment in the deep water Gulf of Mexico during the Late Quaternary. Continental margins form and evolve in response to allogenic and autogenic processes. The East Africa margin is one of the few places in the world where it is possible to observe the effect of continental rifting on the evolution of both continental and marine landscapes. In this last section of the talk, I will show how the East African Rift System (EARS) led to a physiographic change of the western Somali basin, promoting a reorganization of the deepwater drainage system and a shift in ocean bottom circulation.

When: 10:30 am, Wednesday, September 12, 2018

Where: AGC Boardroom, 5th Floor Murray, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Who: Valentina Yanko

Head of the Department of Physical and Marine Geology
Head of the Laboratory of Marine Geology and Geochemistry
Head of the Scientific and Educational Center of Geoarchaeology
Marine and Environmental Geology (SECGMEG)
Odessa I. I. Mechnikov National University, Ukraine

What: Degassing of the Black Sea Bottom under global climate change: significance for environment, geological exploration and navigation

The Black Sea basin contains great resources of methane gas stored in form of gas hydrates beneath sea floor, the amount of which is believed higher than in any other known gas reservoir on Earth. Gas related features e.g. submarine volcanoes, gas seeps, and gas bogs release methane to water column. The project is focussed on mapping these features on the Black Sea shelf and slope and on understanding energy resources and related geohazards in the world's largest (428,000 km2) meromictic basin. This research is relevant to energy policy makers and coastal managers who deal with environmental hazards and sustainable development in the region under the Global Climate Change. The presentation will address the current knowledge of the methane resources and seep-related features in the Black Sea, and discuss approaches, significance and benefits of the research into methane degassing.

When: 10:30 am, Wednesday, August 1, 2018

Where: AGC Boardroom, 5th Floor Murray, Bedford Institute of Oceanography, Dartmouth, Nova Scotia

Last Modified: 2018-10-25