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Supplementary material to “Continental Transform Basins: Why Are They Asymmetric?”
26 January 2010
Leonardo Seeber, Lamont-Doherty Earth Observatory, Palisades, New York
Christopher Sorlien, Institute of Crustal Studies, University of California, Santa Barbara
Michael Steckler, Lamont-Doherty Earth Observatory, Palisades, New York
Marie-Helene Cormier, University of Missouri, Columbia
Citation:
Seeber, L., C. Sorlien, M. Steckler, and M.-H. Cormier (2010), Continental transform basins: Why are they asymmetric?, Eos Trans. AGU, 91(4), 29–30. [Full Article (pdf)]
Figure S1. Plate tectonics of the eastern Mediterranean (A). Anatolia moves westward because it is squeezed and pushed by Arabia-Asia convergence and is pulled by rollback subduction along the Hellenic arc. The right-lateral North Anatolian fault (NAF) and left-lateral Eastern Anatolian fault (EAF) are continental transforms carrying most of this motion. In the Marmara Sea area (B; boxed in A) the NAF has many bends and is flanked by basins and highs. NAF-N and NAF-S are the northern and southern branches of the NAF. Dotted trace marks the two M7.4 and M7.2 earthquake ruptures in 1999. The box marks the area in Figure 1. (Redrawn from Seeber et al., 2006)
Figure S2. The Ridge Basin started forming in the Miocene along the San Gabriel fault (SGF), a strand of the right-lateral San Andreas transform (SAF) in southern California. This basin kept growing for 14 my until a new strand of the SAF shunted and deactivated the SGF in the Pliocene. In the current thrusting regime, it has been uplifted and dissected. The basin was only partially filled with marine sediment during the first 3 million years of development (Castaic Formation), as the Marmara Sea basins are now. Afterwards the sediment was fluvial and lacustrine (Ridge Formation) and the basin was full. The Violin Breccia was deposited along the fault-scarp and is present in both marine and terrestrial settings of the basins. Note structural similarities with the active Marmara basins depicted in Figure 1. In all cases the faults dip toward the concave side of the bend; the basins develop on that side, the hangingwall side, and on the extensional flank 'downstream' of the bends, by oblique-normal slip on the faults. The bend is thus fixed onto the convex side. The depocenter, where subsidence is fastest at any one time, is on the concave side and migrates 'upstream' at the velocity of the fault so as to remain at the same place relative to the bend. Gradually, the normal component of slip decreases away from the bend, thus tilting the sediments toward the bend and forming the shingled sequence. Modified from Crowell [2003] and Link [2003].
Reference:
Link, M. H. (2003), Depositional systems and sedimentary faciesof the Miocene-PlioceneRidge Basin, southern California, in Evolution of Ridge Basin, Southern California, An Interplay Of Sedimentation and Tectonics, edited by J. C. Crowell, Spec. Pap. Geol. Soc. Am., 367, 1–15.
Crowell, J. C. (2003), Introduction to geology of Ridge Basin, southern California, in Evolution of Ridge Basin, Southern California: An Interplay of Sedimentation and Tectonics, edited by J. C. Crowell, Spec. Pap. Geol. Soc. Am., 367, 1–15.
Seeber, L., M.-H. Cormier, C. McHugh, Ö. Emre, A. Polonia, and C. Sorlien (2006), Rapid subsidence and sedimentation from oblique slip near a bend on the North Anatolian Transform in the Marmara Sea, Turkey, Geology, 34, 933–936, doi:10.1130/g22520A.1.