Structural Inheritance and Rapid Rift‐Length Establishment in a Multiphase Rift: The East Greenland Rift System and its Caledonian Orogenic Ancestry

Abstract

We investigate (i) margin-scale structural inheritance in rifts and (ii) the time scales of rift propagation and rift length establishment, using the East Greenland rift system (EGR) as an example. To investigate the controls of the underlying Caledonian structural grain on the development of the EGR, we juxtapose new age constraints on rift faulting with existing geochronological and structural evidence. Results from K-Ar illite fault dating and syn-rift growth strata in hangingwall basins suggest initial faulting in Mississippian times and episodes of fault activity in Middle-Late Pennsylvanian, Middle Permian, and Middle Jurassic to Early Cretaceous times. Several lines of evidence indicate a close relationship between low-angle late-to-post-Caledonian extensional shear zones (CESZs) and younger rift structure: (i) reorientation of rift fault strike to conform with CESZs, (ii) spatial coincidence of rift-scale transfer zones with CESZs, and (iii) close temporal coincidence between the latest activity (late Devonian) on the preexisting network of CESZs and the earliest rift faulting (latest Devonian to earliest Carboniferous). Late-to post-Caledonian extensional detachments therefore likely acted as a template for the establishment of the EGR. We also conclude that the EGR established its near-full length rapidly, i.e., within 4-20% of rift life. The "constant-length model" for normal fault growth may therefore be applicable at rift scale, but tip propagation, relay breaching, and linkage may dominate border fault systems during rapid lengthening.

Terrane Boundary Reactivation, Barriers to Lateral Fault Propagation and Reactivated Fabrics: Rifting Across the Median Batholith Zone, Great South Basin, New Zealand

“…The WNW‐trending Terrane Boundary Fault is oriented at a high angle to the NE‐trending faults of the Great South Basin (Figure ). While it is possible that local stress perturbations relating to preexisting structures led to the development of non‐optimally oriented structures such as the TBF (e.g., Morley, ; Philippon et al, ; Phillips et al, ; Rotevatn, Kristensen, et al, ; Samsu et al, ), we do not think that this is the case due to the subperpendicular geometric relationship between the Terrane Boundary Fault and other NE‐trending faults. Based on geometric relationships between the NE‐ and E‐trending basement fabrics (Figures and c), we suggest that the WNW‐trending structures formed prior to the NE‐trending faults and fabrics.…”

Extensional fault and fold growth: Impact on accommodation evolution and sedimentary infill

“…Pronounced lateral fault segmentation with separated depocenters contrasts rapid length attainment of fault systems and early coalesced depocenters in reactivated rifts as described by e.g. Walsh et al (), Henstra et al () and Rotevatn, Kristensen et al (). However, considering the mode of reactivation is important; upward propagation of previously established faults seems to have been the principal mode of reactivation in the studies by Walsh et al (), Henstra et al (), Rotevatn, Kristensen et al ().…”

“…Walsh et al (), Henstra et al () and Rotevatn, Kristensen et al (). However, considering the mode of reactivation is important; upward propagation of previously established faults seems to have been the principal mode of reactivation in the studies by Walsh et al (), Henstra et al (), Rotevatn, Kristensen et al (). In the Fingerdjupet Subbasin, on the other hand, vertically decoupled faulting and reactivation through dip linkage is documented for three of the extensional phases herein.…”

“…The vertically decoupled faulting likely allowed for lateral fault segmentation and thus a slower attainment of final fault length compared to other 984 | EAGE SERCK and BRaaTHEn studies of reactivated rift faults (e.g. Rotevatn, Kristensen et al, 2018b).…”

“…Prosser, 1993;Gupta, Cowie, Dawers, & Underhill, 1998;McLeod et al, 2002;Leppard & Gawthorpe, 2006). In multiphase rifts, fault reactivation leads to rapid attainment of fault lengths (Henstra, Gawthorpe, Helland-Hansen, Ravnås, & Rotevatn, 2017;Rotevatn, Kristensen et al, 2018b;.…”