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Plate Tectonic Reconstructions of the Cretaceous and Cenozoic Ocean Basins

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Plate Tectonic Reconstructions of the Cretaceous and Cenozoic Ocean Basins Tectonophysrs, 155 (1988) 27-48 Elsevier Science Publishers B.V.. Amsterdam - Printed in The Netherlands Plate tectonic reconstructions of the Cretaceous and Cenozoic ocean basins CHRISTOPHER R. SCOTESE I, LISA M. GAHAGAN ’ and ROGER L. LARSON ’ ’ Shell Deuelopment Co.. Beilarre Research Center, P.O. Box Ml. Houston. TX 77001 (U.S.A. I ’ The Department ofGeological Soences, The Unwer.r# of Texas. Austtn. TX 7X713 (l!S.A.) and The Instrtutefor Geophvsics. Universit,: of Texcrs, Austrn. TX 78759 (U.S.A.) -’ School of 0ceanograph.v. Uniuerslt_v of Rhode Island, kbgston, RI 0_‘8XI (U.S.A.) (Received May 18, 1987: revised vrersion accepted September 8. 19x7) Abstract Scotese. C.R.. Gahagan. L.M. and Larson, R.L.. 1988. Plate tectonic reconstructions of the Cretnceous and Cenozoic ocean basins. In: C.R. Scotese and W.W. Sager (Editors), Mesozoic and Cenozoic Plate Reccm\tructions. Tectonophysics. 155: 27-48. In this paper we present nine reconstructions for the Mesozoic and Cenozoic. based on previously published sea-floor spreading tsochrons*. The purpose of this study was (1) to determine if the isochrons could he refitted to produce accurate plate tectonic reconstructions. (2) to identify areas of apparent mismatch between magnetic iaochrons as a focus for further investigations, and (3) to test the capabilities and accuracy of interactive computer graphic methods of plate tectonic reconstruction. In general. Tertiary and Late Cretaceous isochrons could be refitted wtth little overlap and few gaps: however. closure errors were apparent in the vicinity of the Bouvet and Macquarie triple Junctions. It was not possible to produce Early Cretaceous reconstructions that were consistent with the previously published isochrons. In this paper we also propose that the Late Cretaceous and Early Tertiary plate reorganizations ob\erved in the Indian Ocean were the result of the progressive subduction of an intra-Tethyan rift system. Introduction ceous (chron MO, 118.7 Ma) and Early Cretaceoua (chron M17, 143.8 Ma). The isochrons were drawn In 1985 a map illustrating the age of the ocean using published and unpublished magnetic basins and continents was published by Larson et anomalies and bathymetric information. and were al. (1985) (Fig. l), on which the oceans were modified to take into account new data from divided into colored regions bounded by magnetic Seasat altimetry (Haxby, 1985). This map super- isochrons representing the following geologic time cedes the maps of the age of the ocean floor intervals: Pleistocene (chron 2, 1.9 Ma), Pliocene published by Pitman III et al. (1974) and Sclater (chron 3a, 5.9 Ma), Miocene (chron 6b, 23 Ma), et al. (1981). Oligocene (chron 15, 37.7 Ma), Eocene (chron 25. In this study, we have used interactive com- 59.2 Ma), Paleocene (chron 29, 66.2 Ma), Late puter graphics to produce plate tectonic recon- Cretaceous (chron 34, 84.0 Ma), Middle Creta- structions for each of the sea-floor spreading iso- chrons described by Larson et al. (1985). The goals of this investigation were (1) to determine if ____ * Larson et al. (1985). the isochrons mapped by Larson et al. could be 0040.1951/88/$03.50 ‘1’)1988 Elsevier Science Publishers B.V. Fig. 1. Isochron map illustrating the age of the ocean basm.s (modified after Larson et al., 1985). Fine light stipple-chrons 1. 3a and 6, fine dark stipple-chrons 15 and 25. coarse light stipple- --chrons 29 and 34, coarse dark stipple---chrons MO and Ml?. Continental sutures after Scotese et al. (1979), Ziegler et al. (1983) and Ross and Scotese (this issue). refitted to produce accurate plate tectonic recon- digitizing program was to convert X and Y map structions, (2) to identify the areas of apparent coordinates into coordinates of latitude and longi- mismatch between magnetic isochrons as a focus tude, the program also recorded important infor- for further study and (3) to test the capabilities mation that was used to build a geographic data- and accuracy of interactive computer graphic base. This database consisted of bibliographic in- methods of plate tectonic reconstruction. In the formation as well as a description of the age of the following sections we outline the methods used to feature, the plate with which it was travelhng, and produce the reconstructions, discuss how well the a simple coded description of the feature that was isochrons can be refitted, review the major plate being digitized (for example, BA = bathymetric tectonic events illustrated in Figs. 3-11, and con- contour, RI = spreading ridge, CS = coastline, sider the predictions made for relative plate mo- etc.). This information was later used by data tions across complex plate circuits. management programs that searched and sorted the data, and by the interactive computer graphics M&hods and map-making programs that rotated and plotted the data as a function of plate identifica- Digitization of map data and interactive computer tion and age. graphics After the map data had been digitized, the geographic data was displayed and m~ipulated The first step in our procedure was to encode using the Evans and Sutherland PS300 interactive map data into digital form. This was done using a computer graphics system and the Megadrifter large digitizing tablet and a computer program program (MI. Ross and CR. Scotese). This pro- that converted X and Y map coordinates into gram displays geographic information in three di- latitude and longitude coordinates (Scotese and mensions on the surface of the globe. The user Eaker, 1975). Although the main function of the visually determines best-fitting rotations by inter- 29 b 60 B’N C 55 ?N Fig. 2. Contour piot representing a surface whose peak is the location of best-fittmg Euler poles for the closure of South Atlantic isochrons for (a) chron 25, (b) chron 15 and (c) chron 6. The star represents the Euler poIe determined using interactive graphic>. the dot is the location of the best-fitting Euler pole determined using the method of McKenzie and Sclater (1971). Pilger (1978) and Pattiat (1983). actively manipulating dials that control the loca- Gruphicul test of the best fit tion and amount of rotation about finite rotation poles (LePichon et al.. 1973). By rotating the dials The computer graphic approach described and adjusting the finite rotation pole, isochrons above represents a novel way of making plate can he visually superimposed, and in a matter of reconstructions. However, it is reasonable to en- minutes, a visual best fit can be determined. quire “how well can the isochrons be recon- The main advantages of interactive computer structed using this technique?” To answer this graphics for plate reconstructions are (1) it is question, the rotations that were determined visu- possible to test all possible plate tectonic reassem- ally using the interactive computer graphic method blies in a matter of minutes, (2) reconstruction of were compared with best-fitting rotations that were multiple plates simultaneously is possible, and (3) determined by iterative statistical techniques. In the production of plate reconstructions that in- Fig. 2, the locations of the best-fitting rotations tegrate both marine- and land-based information determined by the interactive computer graphics is enabled. At present, the main disadvantage of method (star) can be compared with the location the method is that there is no numerical quantifi- of the best~fitting rotations (dot) calcufated by cation of the goodness of fit. _ _,- .-_-I_lI,” 34 35 ‘- 3x ai % -E -0 . 39 iterative statistical methods (McKenzie and Late Tertiary: Chrons 2, 3a und 6h (Figs. 3. 4 and Sclater, 1971; Pilger Jr., 1978; Patriat, 1983). 5) Figure 2a is a contour plot that represents a surface whose peak is the location of a finite There is generally a good fit of the magnetic rotation pole (54.80”N-31.80’W) that best fits isochrons that were used to produce the re- chron 25 on the African plate with its counterpart constructions for the Late Tertiary (chrons 2. 3a on the South American plate. Similar contour and 6b). The only areas of notable misfit occur plots of the best-fit surface were made for chron along the northwestern extension of the Central 15 and chron 6 in the South Atlantic (Figs. 2b and Indian Ridge in the Arabian Sea. between the c). In both cases. the finite rotation pole de- Nazca and Pacific plates. and in the vicinity of the termined by the interactive computer graphic triple junction between Australia. Antarctica and method falls close to the calculated best-fit pole. the Pacific plates, south of Macquarie Ridge. We feel that this graphic test indicates that the The major tectonic events during the Late Ter- rotations determined by the interactive technique tiary (Figs. 3, 4 and 5) include the continued are comparable to results obtained using iterative northward motion of India and Australia; the statistical techniques, and that we are justified in opening of the Red Sea (Cochran, 1983: Hemp- using this method to produce plate reconstruc- ton, 1987: Labrecque and Zitellini, 1985). the Gulf tions. However. we agree that a combination of of California (Larson et al.. 1968: Atwater, 1970) these techniques might be the best approach, and and the Sea of Japan (Otsuki and Ehiro. 1979); are planning to modify the computer graphics the convergence and sinistral strike-slip movement software in the near future so that estimates of the along the Alpine Fault in New Zealand (Kamp, goodness of fit can be calculated interactively. 1986) and the breakup of the Farallon plate to form the Cocos and Nazca plates (Menard. 1978; Wortel and Cloetingh. 1981). The evolution of the Caribbean region is based on recent syntheses by Pindell and Barrett (1987) and Ross and Scotese Mesozoic and Cenozoic plate tectonic reconstruc- (this issue).
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