Controls of Basement Fabric on the Linkage of Rift Segments

Heilman, Erin; Kolawole, Folarin; Atekwana, Estella A.; Mayle, Micah

doi:10.1029/2018tc005362

Cited by 50 publications

(93 citation statements)

References 98 publications

(278 reference statements)

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“…There are multiple geometric and kinematic interactions between basement shear zones and rift‐related faults. Rift‐related faults have previously been shown to exploit internal mylonitic layers within shear zones (Gontijo‐Pascutti et al, ; Heilman et al, ; Kirkpatrick et al, ; Morley, ; Paton & Underhill, ; Salomon et al, ), with examples also documented from the northern North Sea rift (Figure ; “exploitative” interaction of Fazlikhani et al () and Phillips et al ()). Numerical and analog modeling has shown that rocks containing a fabric are weaker, and thus more likely to fail, along said fabric when subject to favorably oriented stress fields (Chattopadhyay & Chakra, ; Tong & Yin, ; Youash, ; Zang & Stephansson, ).…”

Section: Discussionmentioning

confidence: 98%

The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

et al. 2019

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The northern North Sea rift evolved through multiple rift phases within a highly heterogeneous crystalline basement. The geometry and evolution of syn-rift depocenters during this multiphase evolution and the mechanisms and extent to which they were influenced by preexisting structural heterogeneities remain elusive, particularly at the regional scale. Using an extensive database of borehole-constrained 2D seismic reflection data, we examine how the physiography of the northern North Sea rift evolved throughout late Permian-Early Triassic (RP1) and Late Jurassic-Early Cretaceous (RP2) rift phases, and assess the influence of basement structures related to the Caledonian orogeny and subsequent Devonian extension. During RP1, the location of major depocenters, the Stord and East Shetland basins, was controlled by favorably oriented Devonian shear zones. RP2 shows a diminished influence from structural heterogeneities, activity localizes along the Viking-Sogn graben system and the East Shetland Basin, with negligible activity in the Stord Basin and Horda Platform. The Utsira High and the Devonian Lomre Shear Zone form the eastern barrier to rift activity during RP2. Toward the end of RP2, rift activity migrated northward as extension related to opening of the proto-North Atlantic becomes the dominant regional stress as rift activity in the northern North Sea decreases. Through documenting the evolving syn-rift depocenters of the northern North Sea rift, we show how structural heterogeneities and prior rift phases influence regional rift physiography and kinematics, controlling the segmentation of depocenters, as well as the locations, styles, and magnitude of fault activity and reactivation during subsequent events.

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Section: Discussionmentioning

confidence: 98%

The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

et al. 2019

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“…The Malawi Rift (henceforth MR) (Figures 2a and 2b), which is the southern segment of the western branch of the EARS, extends for~900 km from southern Tanzania, through Malawi, to northern Mozambique. The rift is largely magma poor except for the Pliocene-Pleistocene RVP located in northern tip of the rift (e.g., Ebinger et al, 1989;Fontijn et al, 2012;Heilman et al, 2019). From north to south, the first 550 km extent of the rift is occupied by Lake Malawi, which has a width ranging between 50 and 75 km.…”

Section: Tectonic Setting and Architecture Of The Malawi Riftmentioning

confidence: 99%

“…Globally, there is ample support for magma-assisted rifting provided by the occurrence of surface magmatism associated with many rift systems such as the eastern branch of the East African Rift System (EARS; Figure 1; Ebinger, 2005;Kendall et al, 2005). However, numerous examples also exist worldwide where rifting is accompanied by limited exposure of volcanic rocks, such as in the Rio Grande Rift (Wilson et al, 2005) and the Malawi Rift, which is the focus of this study and represents the southern segment of the western branch of the EARS (e.g., Ebinger et al, 1989;Fontijn et al, 2012;Heilman et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Lithospheric Structure of the Malawi Rift: Implications for Magma‐Poor Rifting Processes

et al. 2019

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Our understanding of how magma‐poor rifts accommodate strain remains limited largely due to sparse geophysical observations from these rift systems. To better understand the magma‐poor rifting processes, we investigate the lithospheric structure of the Malawi Rift, a segment of the magma‐poor western branch of the East African Rift System. We analyze Bouguer gravity anomalies from the World Gravity Model 2012 using the two‐dimensional (2‐D) radially averaged power‐density spectrum technique and 2‐D forward modeling to estimate the crustal and lithospheric thickness beneath the rift. We find: (1) relatively thin crust (38–40 km) beneath the northern Malawi Rift segment and relatively thick crust (41–45 km) beneath the central and southern segments; (2) thinner lithosphere beneath the surface expression of the entire rift with the thinnest lithosphere (115–125 km) occurring beneath its northern segment; and (3) an approximately E‐W trending belt of thicker lithosphere (180–210 km) beneath the rift's central segment. We then use the lithospheric structure to constrain three‐dimensional numerical models of lithosphere‐asthenosphere interactions, which indicate ~3‐cm/year asthenospheric upwelling beneath the thinner lithosphere. We interpret that magma‐poor rifting is characterized by coupling of crust‐lithospheric mantle extension beneath the rift's isolated magmatic zones and decoupling in the rift's magma‐poor segments. We propose that coupled extension beneath rift's isolated magmatic zones is assisted by lithospheric weakening due to melts from asthenospheric upwelling whereas decoupled extension beneath rift's magma‐poor segments is assisted by concentration of fluids possibly fed from deeper asthenospheric melt that is yet to breach the surface.

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“…As the extension direction was oriented at a high angle to the WNW-trending Terrane boundary, this structure does not appear to have been active during this rift phase. However, the presence of the Terrane boundary Shear Zone, and the granitic laccoliths beneath the TBF Footwall Block, blocked the lateral propagation of faults forming at this time and acted to segment the overall rift (Figure 13b) (Corti, 2008;Dore et al, 1997;Heilman et al, 2019;Henstra et al, 2015;Koopmann et al, 2014;Peace et al, 2017).…”

Section: 1029/2019tc005772mentioning

confidence: 99%

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

Phillips

McCaffrey

2019

Tectonics

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Prominent preexisting structural heterogeneities within the lithosphere may localize or partition deformation during tectonic events. The NE‐trending Great South Basin, offshore New Zealand, formed perpendicular to a series of underlying crustal terranes, including the dominantly granitic Median Batholith Zone, which along with the boundaries between individual terranes exert a strong control on rift physiography and kinematics. We find that the crustal‐to‐lithospheric scale southern terrane boundary of the Median Batholith Zone is associated with a crustal‐scale shear zone that was reactivated during Late Cretaceous extension between Zealandia and Australia. This reactivated terrane boundary is oriented at a high angle to the faults defining the Great South Basin. We identify a large granitic laccolith along the southern margin of the Median Batholith, expressed as subhorizontal packages of reflectivity and acoustically transparent areas on seismic reflection data. The presence of this strong granitic body inhibits the lateral southwestward propagation of NE‐trending faults, which segment into a series of splays that rotate to align along the margin as they approach. Further, we also identify two E‐W‐ and NE‐SW‐oriented basement fabrics, likely corresponding to prominent foliations, which are exploited by small‐scale faults across the basin. We show that different mechanisms of structural inheritance are able to operate simultaneously, and somewhat independently, within rift systems at different scales of observation. The presence of structural heterogeneities across all scales needs to be incorporated into our understanding of the structural evolution of complex rift systems.

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Controls of Basement Fabric on the Linkage of Rift Segments

Cited by 50 publications

References 98 publications

The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

Lithospheric Structure of the Malawi Rift: Implications for Magma‐Poor Rifting Processes

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

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