Influence of Sediment Input and Plate‐Motion Obliquity on Basin Development Along an Active Oblique‐Divergent Plate Boundary: Gulf of California and Salton Trough

Abstract

Transtensional basins have formed along the Pacific-North America plate boundary in the Gulf of California and Salton Trough region during Late Cenozoic time. Axial basins occupy a 50-60 km wide belt along the main plate boundary, and change from sedimentstarved oceanic spreading centers in the south that are oriented perpendicular to long NW-striking transform faults, to oblique N-trending pull-apart (stepover) basins in the north that contain thick sediments and lack evidence for normal oceanic crust. Marginal basins are found along the flanks of the Gulf-Trough corridor and consist mainly of supradetachment basins (only in the north), transtensional fault-termination basins, and classic orthogonal rift basins.A review of previous studies suggests that three main parameters govern the structural style, composition, and total thickness of sedimentary basins in this setting: (1) the rift angle (a), defined as the acute angle between the overall trend of the plate boundary and the direction of relative plate motion; (2) proximity to voluminous input of sediment from the Colorado River and other smaller drainages in the north; and (3) the degree of strain partitioning. Detachment faults and supradetachment basins are well documented in the northern Gulf and Salton Trough where a ! 30 , whereas no detachment faults are recognized in the central and southern Gulf of California (a < 20 ). We suggest that faster extension associated with a higher rift angle is the main factor responsible for creation of supradetachment basins in the northern region.Voluminous input of sediment derived primarily from the Colorado River exerts a first-order control on crustal thickness and composition, lithospheric mechanics, and rift architecture. In the sediment-starved southern Gulf of California, the plate boundary has completed the transition from continental rifts to seafloor spreading centers with normal ocean crust and magnetic lineations. The Guaymas spreading center in the central Gulf has young oceanic crust with an upper layer of sediments and shallow intrusions. In contrast, sediment-filled and overfilled basins in the north are characterized by thick new transitional crust that is formed by input and magmatic modification of sediment, which fills the new space created by lithospheric rupture and oblique divergence. Thus the rate of sediment input appears to determine whether or not continental rifting progresses to the ultimate formation of a new ocean basin floored by normal basaltic crust.

Stratigraphic record of basin development within the San Andreas fault system: Late Cenozoic Fish Creek-Vallecito basin, southern California

“…The volume of sediment in the basins is roughly equal to material eroded from the Colorado Plateau in the past 5-6 m.y., and it contributes to crustal growth along the plate boundary at rates similar to those documented for subductionrelated magmatic arcs and seafl oor spreading centers (Dorsey, 2010). Although input of sediment clearly affects thermal structure, crustal rheology, and deformation style in this setting (Persaud et al, 2003;González-Fernández et al, 2005;Lizarralde et al, 2007;Bialas and Buck, 2009;Dorsey and Umhoefer, 2010), little is known about the interplay between crustal subsidence and Pliocene progradation of the Colorado River delta into and across the Salton Trough basin. This paper presents the results of an integrated fi eld, stratigraphic, paleomagnetic, and geohistory analysis of the Fish Creek-Vallecito basin in the western Salton Trough (Fig.…”

The time scales of continental rifting: Implications for global processes

“…One class is orogenic rifts within late-stage collisional belts where the crust has been thickened and heated by thrust faulting and/or magmatism, leading to a broad zone of extensional deformation within weak lithosphere (e.g., Buck, 1991;Brun, 1999;Lavier and Manatschal, 2006). Active examples are the Basin and Range Province that extended thickened crust (e.g., Hamilton, 1987;Buck, 1991;Kreemer and Hammond, 2007), the Gulf of California, where rifting initiated immediately after arc volcanism (e.g., Stock and Hodges, 1990;Dorsey and Umhoefer, 2012), and the incipient rift zones of the Apennines (e.g., Jolivet et al, 1998). A second class is cratonic rifts underlain by relatively strong crust and thick lithosphere far from subduction or collisional zones, leading to strain localization in a single rift zone with narrow, deep basins (e.g., Weissel and Karner, 1989;Buck, 1991).…”

“…2). This along-axis segmentation effectively partitions stratigraphic sequences and strongly infl uences erosion and drainage patterns in rifts (e.g., Gawthorpe and Leeder, 1997;Mats et al, 2000;Densmore et al, 2004;Dorsey and Umhoefer, 2012). Initially discrete border-fault segments interact and are mechanically connected through transfer faults and relay ramps oriented obliquely to the strikes of border faults (e.g., Larsen, 1988;Morley and Nelson, 1990;Walsh and Watterson, 1991;Peacock and Sanderson, 1994).…”

Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

“…1). Dorsey & Umhoefer (2012) further suggest that the high rate of sediment input from the Colorado River plays a major role in delaying the creation of new magnetized oceanic crust in the northern Gulf and Salton Trough regions compared to the central Gulf (Guaymas Basin). The influence of sediment input at both early and late stages of rifting may be what distinguishes the northern and central-southern rift segments.…”