Analogue Modeling of Plate Rotation Effects in Transform Margins and Rift‐Transform Intersections

Abstract

Transform margins are first-order tectonic features that accommodate oceanic spreading.Uncertainties remain about their evolution, genetic relationship to oceanic spreading, and general structural character. When the relative motion of the plates changes during the margin evolution, further structural complexity is added. This work investigates the evolution of transform margins and associated rift-transform intersections, using an analogue modeling approach that simulates changing plate motions. We investigate the effects of different crustal rheologies by using either (a) a two-layer brittle-ductile configuration to simulate upper and lower continental crust, or (b) a single layer brittle configuration to simulate oceanic crust. The modeled rifting is initially orthogonal, followed by an imposed plate vector change of 7°that results in oblique rifting and plate overlap (transpression) or underlap (transtension) along each transform margin. This oblique deformation reactivates and overprints earlier orthogonal structures and is representative of natural examples. We find that (a) a transtensional shift in the plate direction produces a large strike-slip principal displacement zone, accompanied by en-echelon oblique-normal faults that accommodate the horizontal displacement until the new plate motion vector is stabilized, while (b) a transpressional shift produces compressional structures such as thrust fronts in a triangular zone in the area of overlap. These observations are in good agreement with natural examples from the Gulf of California (transtensional) and Tanzania Coastal Basin (transpressional) shear margins and illustrate that when these deformation patterns are present, a component of plate vector change should be considered in the evolution of transform margins.Plain Language Summary Tectonic plate boundaries on our planet are categorized by their relative motion with respect to each other. The three main categories are those moving away, toward, and parallel to one another. We study the processes occurring when two tectonic plates moving parallel begin to rotate and move away or toward each other. Currently, this is occurring in the Gulf of California, and in the past, it occurred in areas such as the Southern Atlantic, creating the segmented pattern along its midocean ridge. To study these tectonic plate boundaries, we use sandbox modeling. We make miniature models of the Earth's crust with silicone putty and sand and recreate the same movements that tectonic plates go through. This allows us to understand the structures created in such environments better. The pattern and the height or depth of these structures are related to how fast the plates move. This work can help recognize areas where similar deformation has occurred in the past, which is important for hydrocarbon exploration. It can also assist with geothermal energy exploration, as areas where plates move parallel and away from each other present good opportunities for hotter temperatures in the subsurface.

Segmentation of Rifts Through Structural Inheritance: Creation of the Davis Strait

“…Results from our modeling show the impact of mantle lithosphere scarring related to a Palaeoproterozoic orogenic event in the development of the complex Mesozoic-Cenozoic rifting and ocean basin formation between Greenland and Canada ( Figure 5), and highlight the potential role of obliquity in the rift evolution (Figure 7). Although a number of studies have previously modeled oblique rifting in three dimensions (Brune et al, 2014;May et al, 2015;Zwaan et al, 2016;Zwaan & Schreurs, 2017;Brune et al, 2017;Farangitakis et al, 2019), our study shows tectonic features related to West Greenland and offers a new geodynamic explanation for the Phanerozoic rift event in the region. Figure 10 outlines a mechanism for the evolution of the Davis Strait during the Paleocene.…”

The structural evolution of pull‐apart basins in response to changes in plate motion

“…We use a modified experimental apparatus based on Farangitakis et al. (2019; originally inspired by Basile & Brun, 1999), where a moving plate slides away from a static plastic sheet at the base of a brittle/ductile layer configuration (Figure 4a). Hence, deformation is entirely driven through the applied basal boundary conditions, with pre‐imposed velocity discontinuities (VDs), similar to those in Allemand and Brun (1991) and Tron and Brun (1991).…”

“…However, it can be applied to other examples around the world with similar structure (as seen in Reber et al, 2020), and we extend our study with a comparison to the Bohai Basin. For a parametric study on the effects of transtension and transpression on strike-slip boundaries with a similar apparatus, we refer readers to Farangitakis et al (2019). Relative motion between the basal plates varies during the first cm of deformation and deviates from purely orthogonal by ~0.5° due to experimental conditions.…”

“…A transtensional component is sufficient to create two to three times more accommodation space for sediments compared to an orthogonal pull‐apart basin (ten Brink et al., 1996). Transtensional pull‐apart basins also form wider PDZs (Farangitakis et al., 2019), comprising transtensional zones ranging from elongate negative flower structures to complex zones with mini‐basin characteristics themselves (Figure 1b). A transtensional pull‐apart basin thus has a distinct form and evolutionary history compared with classic, purely strike‐slip pull‐apart basins.…”

Early Neoproterozoic Deformation Kinematics in the Chottanagpur Gneiss Complex (Eastern India): Evidence from the Curvilinear Hundru Falls Shear ZoneAnalysis

“…Reorganization of early-formed deformation structures during progressive deformation is widely reported [36,[51][52][53][54]. Emerging data suggests that changing convergence vectors during plate motions can play a major part in the development of new structures that reorient earlier fabrics in the rocks [176][177][178][179][180].…”