Full text loading...
-
Approaching the Meaning of Regional Unconformities of Tectonic Origin Present in Passive Margins from a Numerical-modelling Perspective
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
Understanding the formation of unconformities is key to unravel the history of rifted margin formation. Available data, does not always provide enough information to relate unconformities and rift evolution. Here, we explore the tectonic meaning of unconformities by using numerical models, which reproduce different modes of extension.
We find that regional unconformities occur due to migration of extension from one sector of the margin towards another. For intermediate strength crust, sequential faulting, younging towards the ocean, leads to the formation of asymmetric basins and to progressively younger syn- and post-kinematic sediments ocean-wards. Thus, the unconformity that separates syn-kinematic sediments from sag-fill sediments, dates the beginning of the sequential faulting phase and is diachronous along the basin. For weak crusts, a first phase of rifting occurs along a wide area, followed by a narrow rifting phase that ends in crustal break-up. In this case, localization of the deformation in the narrow rifting phase results in an unconformity that separates syn- from post-kinematic sediments. Although, these modelled unconformities have all the geometric characteristics of break-up unconformities, they form before break-up. Consequently, the coupled use of thermo-mechanical and stratigraphic modelling is key to complement seismic interpretation of unconformities, reducing exploration risk.