Thick deltaic sedimentation and detachment faulting delay the onset of continental rupture in the Northern Gulf of California: Analysis of seismic reflection profiles

Abstract

[1] The transition from distributed continental extension to the rupture of continental lithosphere is imaged in the northern Gulf of California across the obliquely conjugate Tiburón-Upper Delfin basin segment. Structural mapping on a 5-20 km grid of seismic reflection lines of Petroleos Mexicanos demonstrates that~1000% extension is accommodated on a series of NNE striking listric-normal faults that merge at depth into a detachment fault. The detachment juxtaposes a late-Neogene marine sequence over thinned continental crust and contains an intrabasinal divide due to footwall uplift. Two northwest striking, dextral-oblique faults bound both ends of the detachment and shear the continental crust parallel to the tectonic transport. A regional unconformity in the upper 0.5 s (two-way travel time) and crest erosion of rollover anticlines above the detachment indicates inversion and footwall uplift during the lithospheric rupture in the Upper Delfin and Lower Delfin basins. The maximum length of new crust in both Delfin basins is less than 40 km based on the lack of an acoustic basement and the absence of a lower sedimentary sequence beneath a wedge-shaped upper sequence that reaches >5 km in thickness. A fundamental difference exists between the Tiburón-Delfin segment and the Guaymas segment to the south in terms of presence of low-angle normal faults and amount of new oceanic lithosphere, which we attribute to thermal insulation, diffuse upper-plate extension, and slip on low-angle normal faults engendered by a thick sedimentary lid.

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“…1) (Oskin and Stock, 2003;Bennett et al, 2012), where marine incursion has been well dated as latest Miocene. However, we note that Isla Tiburón is at the southeastern margin of a basin that, in its central part, has >7 km of sediments overlying the Late Cretaceous basement (Martín-Barajas et al, 2013). The well T-1 drilled by PEMEX near the deepest part of the Tiburón Basin encountered ~4.8 km of marine deposits (Helenes et al, 2009), which in their lower part are considered not reworked and have an upper age limit of 11.9 Ma based on the microfossils Ciclycargolithus fl oridanus (known range 37-11.9 Ma), Cribroperdinium tenuitabulatum (69.9-11.63 Ma), Paleocystodinium golzowense (56-9.2 Ma), and Dapsilidinium pseudocolligerum (56-7.12 Ma) (J.…”

“…Helenes, 2013, written commun.). The recent seismic profi les of Martín-Barajas et al (2013) show that the lowermost sedimentary package pinches out to the south and is not deposited on the basement high at the southeastern margin of the basin (Tiburon shelf and Isla Tiburón).…”

Consag Basin: northern Gulf of California, evidence of generation of new crust, based on seismic reflection data

“…In the northern Gulf there are several tectonically active and inactive rift basins (Persaud et al 2003;González-Escobar et al 2006;Aragón-Arreola and Martín-Barajas 2007;González-Escobar et al 2009;MarHernández et al 2012;Sojo-Amezquita 2012;Martín-Barajas et al 2013). The group of active basins in the northern Gulf includes Wagner, Consag, Upper Delfín, and Lower Delfín.…”

“…It is part of a transtensional rift dominated by the transcurrent right lateral faults that, along with the San Andreas fault of California, form the San Andreas-Gulf of California fault system (Larson et al 1972). Within this transtensional system, deformation takes place along the transcurrent faults as well as along the oblique normal faults that accommodate much of the right lateral movement between the Pacific and North America plates in the Gulf of California region (Fenby and Gastil 1991;Nagy and Stock 2000; Aragón-Arreola and Martín-Barajas 2007; Martin- Barajas et al 2013). Some workers propose that creation and development of the Gulf of California began during the Neogene (Martin-Barajas 2000) and took place in two tectonic stages: (1) orthogonal extension during the middle to late Miocene; and (2) development of major transform faults at the margin between the Pacific and North America plates during the Pliocene (Stock and Hodges 1989).…”

“…Consequently, the bathymetric expression of these two basins does not define the entire structural geometry due to the thick sedimentary cover. Recently, González-Escobar et al (2009, MarHernández et al (2012), and Martin- Barajas et al (2013) reported the depth of the acoustic basement (inferred from seismic two way travel time (TWTT)) of the northern Gulf of California, in some basins, at more than 7 km (Figure 2). At greater depths there is no seismic resolution, so it appears that the depth of the basement must be greater than these depths (>7 km).…”