A reconstruction of the Eurekan Orogeny incorporating deformation constraints

Abstract

The Eurekan Orogeny records Paleogene convergence between Greenland and the Canadian Arctic. The complexity of the region, well represented by the disputed magnitude of Cenozoic sinistral displacement of Greenland relative to Ellesmere Island, stems from the simultaneous evolution of multiple tectonic regimes, as well as overprinting of later tectonic activity. Presented here is a plate model of regional crustal deformation constructed with the interactive GPlates software that enables an evaluation of previous reconstructions of the Eurekan Orogeny. This model is built upon a synthesis of published geological and geophysical data and their interpretations. It incorporates two phases of deformation from ~63 to 35 Ma. Phase 1, ~63 to ~55 Ma, involves ~85 km of Paleocene extension between Ellesmere and Devon Island, extension of ~20 km between Axel Heiberg and Ellesmere Island, and ~85 km of sinistral strike slip along the Nares Strait/Judge Daly Fault System, matching a range of 50–100 km indicated by the offset of marker beds, facies contacts, and platform margins between the conjugate Greenland and Ellesmere Island margins. Phase 2, ~55 to 35 Ma, results in total east‐west compression of ~30 km and ~200 km of north‐south compression across Ellesmere Island. This model confirms, for the first time, that key observations from subregions deformed by the Eurekan Orogeny are compatible on a broad scale. We have also identified potential problem areas in southwestern Ellesmere Island that are less compatible with a best fit model, given current constraints. This deforming plate model offers a platform and base model for future research.

Exhuming the Top End of North America: Episodic Evolution of the Eurekan Belt and Its Potential Relationships to North Atlantic Plate Tectonics and Arctic Climate Change

“…Finally, the Paleocene age group indicates a rapid exhumation pulse at a rate of ≥0.4 km/Myr prior to sediment deposition. We interpret this rapid exhumation as reflecting a generally extensional period related to crustal thinning and tectonic denudation rather than tectonic uplift, because (i) it is coeval with basin formation and deposition in a coastal marine environment (as indicated by the palynology data) and, thus, with subsidence of parts of the continental margin, and (ii) it coincides with a period of crustal extension from Late Cretaceous‐Cenozoic times proposed by interpretation of aeromagnetic and gravity data for the northeastern Canadian Arctic margin (Anudu et al, ) and also predicted between 63 and 55 Ma by GPlates modeling (Gion et al, ; Harrison, ). Crustal thinning may have caused transtensional reactivation of preexisting fault zones, locally leading to pull‐apart(?)…”

“…Assuming geothermal gradients between 20 and 40 °C/km, average denudation rates for the lag time can be estimated between 0.85 and 0.25 km/Myr. Since denudation was presumably related to crustal extension/transtension (Harrison, ; Anudu et al, ; Gion et al, ; see also discussion on the pre‐Eurekan evolution), we consider a higher geothermal gradient to be more realistic and thus estimate denudation rates of ~0.45 to 0.25 km/Myr for the Paleocene, pre‐Eurekan stage, that is, for the time between isotopic closure (~63 Ma) and sediment deposition (~56 Ma). The increasing lag time and decreasing cooling rates from early to late Paleocene argue for an episodic high exhumation pulse during the Early Paleocene.…”

“…The Canadian Arctic must have experienced significant (trans)extension from the Late Cretaceous till at least the end of the Paleocene, as suggested by interpretations of structural data along the Nares Strait (Piepjohn et al, ) and of potential field data from the westernmost Ellesmere and Axel Heiberg islands (Anudu et al, ). An extensional regime in the Paleocene has also been assumed for a GPlates model (Gion et al, ), providing reconstructions with an estimated value of ~85 km of extension between Ellesmere and Devon Islands and of ~20 km of extension between Ellesmere and Axel Heiberg Islands (Harrison, ).…”

Depositional Evolution of the Western Amundsen Basin, Arctic Ocean: Paleoceanographic and Tectonic Implications

“…Sedimentary subunits 1b and 1c (mid-Eocene to mid-Oligocene) correspond to the lower half of the 44-18 Ma depositional hiatus inferred in the original study of the ACEX cores ; Figure 10). This time gap overlaps the main phase of Eurekan compression in North Greenland, Ellesmere Island, and Svalbard from 55 to 33 Ma (e.g., Gion et al, 2016;Oakey & Chalmers, 2012;Oakey & Stephenson, 2008;Piepjohn et al, 2016). Several recent studies suggest that the Eurekan orogeny affected large parts of the Arctic Ocean (Døssing, Hopper, et al, 2013;Døssing et al, 2014;O'Regan et al, 2008).…”

“…Following a prolonged phase of compression during the Eurekan and Svalbardian orogenies from 56 to 33 Ma (O'Regan et al, ), plate reconstructions show that the crust in northeast Greenland and west of Svalbard experienced trans‐extension beginning in the Oligocene around 30 Ma. Major extension followed much later (Gion et al, ). This does not fit with opening a seaway connection already at 36 Ma.…”