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John Evanelatos

ES_GS_2015_JE_210H-214W

Ph. D. Candidate

Department of Earth Sciences

Email: j.evan@Dal.Ca
Phone: +1 902 494 2358
Fax: +1 902 494 6889
Mailing Address:

Dalhousie University
1459 Oxford Street
PO BOX 15000
Halifax NS B3H 4R2
CANADA
 

Office:

  Life Sciences Centre
  4th floor, Ocean Wing
  Rm. 4654
  Floor Plans

Supervisor:

David Mosher

Thesis Title:

Seismic stratigraphy and morphology of Makarov Basin: tectonic implications

The tectonic history of Amerasia Basin, Arctic Ocean, is not well known due to a lack of information and the geological complexity of the region. The lack of information is due to perennial cover of sea ice, making conventional shipborne investigations difficult or impossible. The northern part of Amerasia Basin, comprising Makarov and Podvodnikov basins, and the Alpha, Mendeleev and Lomonosov ridges, is particularly underexplored and understudied. As a result of this lack of knowledge, there exists numerous, often contradictory, tectonic models for the genesis of Amerasia Basin (cf. Døssing et al., 2013; Miller and Verzhbitsky, 2009). The objective of the thesis, therefore, is to gain a better understanding of the origin and evolution of Makarov Basin at the northern limit of the larger Amerasia Basin to help constrain the tectonic evolution of the rest of Amerasia Basin.

This study is divided into four parts: 1) gravity inversion of Makarov Basin, 2) crustal structure of a 2D profile of the basin constrained by coincident multi-channel seismic reflection, seismic refraction and shipborne gravimetric data, 3) seismic stratigraphy of the seismic reflection profile, and 4) morphological analysis using bathymetric data from the area. This seminar will focus on the latter two elements.

The stratigraphic analysis is based on a 400 km seismic reflection line, extending from the Makarov-facing flank of Alpha Ridge to the crest of Lomonosov Ridge via central Makarov Basin. The seismic profile shows a thickening of the sedimentary cover from 0.6 s two-way time on the flank of Alpha Ridge to over 2 s adjacent to Lomonosov Ridge. Basin stratigraphy is divided into four units according to their unique assemblage of seismic facies. Basinward dipping reflections and sedimentary accumulation in the deepest part of the basin suggest sediments were sourced from the Barents Shelf and Lomonosov Ridge prior to opening of Eurasia Basin. Correlations with regional tectonic events indicate that lowermost units 0 and 1 were likely deposited prior to the onset of rifting that created Eurasia Basin (Late Cretaceous). Units 2 and 3 are dominated by seismic facies interpreted as pelagic to hemipelagic successions, suggesting a change in sediment source from the Barents Shelf/Lomonosov Ridge to more distal margins. Stratigraphic correlation from Makarov Basin to Alpha Ridge suggests that the sedimentary drape on Alpha Ridge is mostly Cenozoic and that this section was not subaerially exposed.

Morphological analysis of Makarov Basin and surrounding regions relies on the International Bathymetric Chart of the Arctic Ocean (Jakobsson et al., 2012) supplemented with limited multi-beam bathymetric data. Results show a straight, steep and consistent slope along the flank of Lomonosov Ridge into Makarov Basin, as opposed to the opposite flank of Lomonosov Ridge (into Amundsen Basin) which is segmented. In addition, the Amerasian flank of Lomonosov Ridge exhibits features suggestive of pull-apart basins, shearing and marginal ridges (e.g., Marvin and Geophysics spurs), and possible folding/thrusting. The co-existence of compressional and extensional features is typical of strike-slip (transform) boundaries, as is the steep consistent slope of the Amerasian flank of the ridge.

In conclusion, the seismic stratigraphy and morphology of Makarov Basin are consistent with tectonic models that predict a transform boundary along the Amerasian flank of Lomonosov Ridge. In addition, the undisturbed nature of Cenozoic sediments imposes a minimum age on Makarov Basin.