Browsing by Subject "plate reconstruction"

Now showing 1 - 20 of 40
  • Thumbnail Image
    Item
    A Slide Show for Global Plate Motions from Jurassic to Present Day (Paleoceanographic Mapping Project Report No. 54-0389)
    (Institute for Geophysics, 1989) Mueller, R. Dietmar; Royer, Jean-Yves
    A global model for Mesozoic and Cenozoic plate motions has been developed by the Paleoceanographic Mapping Project (POMP) during the last four years. It is based on a digital tectonic database that includes modern plate boundaries, marine magnetic anomaly data, fracture zone lineations, bathymetric data, Seasat and Geosat altimetry data, mapped ocean-continent boundaries and continental tectonic data. We used this global model to produce a set of 22 slides that display global and regional plate reconstructions, which illustrate the global plate tectonic development of the ocean basins from the breakup of Pangea in the Middle Jurassic to present day. Our reconstructions for the eastern Indian Ocean are consistent with the known seafloor spreading history of the Australian-Antarctic Basin and the Wharton Basin since the Late Cretaceous. In particular, they resolve the problem of overlap between the Kerguelen Plateau and Broken Ridge. An internally consistent plate model for the entire South Pacific region has been developed using a combination of satellite altimetry, magnetic anomaly and bathymetry data. Our closure of the South Atlantic that takes into account intracontinental deformation in Africa and South America does not assume any of the substantial gaps or overlaps that are inherent in rigid plate models. Reconstructions for the North Atlantic region are based on a new compilation of magnetic and fracture zone data.
  • Thumbnail Image
    Item
    Atlas of Mesozoic and Cenozoic Plate Tectonic Reconstructions 1987 (Paleoceanographic Mapping Project)
    (Institute for Geophysics, 1987) Scotese, Christopher R.; Gahagan, Lisa M.; Ross, Malcolm I.; Royer, Jean-Yves; Mueller, R. Dietmar; Nuernberg, Dirk; Mayes, Catherine L.; Lawver, Lawrence A.; Tomlins, Robin L.; Newman, Jerry S.; Heubeck, Christoph E.; Winn, J. Kyle; Beckley, Lila; Sclater, John G.
  • Thumbnail Image
    Item
    Atlas of Mesozoic/Cenozoic reconstructions (200 Ma to Present Day) (PLATES Project, Progress Report No. 01-0192)
    (Institute for Geophysics, 1992) Coffin, Millard F.; Gahagan, Lisa M.; Lawver, Lawrence A.; Lee, Tung-Yi; Rosencrant, Eric.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Depth and Age in the South Atlantic (Paleoceanographic Mapping Project Progress Report No. 40-0888)
    (Institute for Geophysics, 1988) Nuernberg, Dirk
    A significant flattening of the relation between depths and age of ocean floor older than 80 Ma can be explained by assuming that the oceanic lithosphere acts as a thermal boundary layer on top of a viscous upper mantle. In the past, uncertainties of age, of sediment thickness and of bathymetry limited the predictions about this relationship. In this study, recent data from the South Atlantic have been averaged into half by half degree elements, so that the relationship between depth and age can be studied in detail. We constructed a high resolution isochron chart for the South Atlantic using the latest available compilation of magnetic anomaly data and satellite altimetry data. The most recent sediment thickness map is used to correct bathymetry for sediment loading in order to obtain the accurate depth to basement We have plotted the corrected basement depth versus age for the entire South Atlantic as well as for distinct areas. The depth/age relationship is presented as contours about the mode enclosing approximately two thirds of the data. In the South Atlantic, the ocean floor subsides with the square root of age on crust younger than 80 Ma. Beyond 80 Ma depths flatten significantly with age. Moreover, a change of the depth/age relationship for opposite flanks as well as with latitude is obvious, which might be related to small scale convection in the upper mantle.
  • Thumbnail Image
    Item
    Development of the Circum-Pacific Panthallassic Ocean during the Early Paleozoic (Paleoceanographic Mapping Project Report No. 10-0386}
    (Institute for Geophysics, 1986) Scotese, Christopher R.
    Though the Pacific plate is less than 200 million years old, the Circum-Pacific ocean basin (Panthallassic ocean basin) has probably been in existence since Precambrian times. During the Early Paleozoic the Tasman trans-Antarctic, arid southern Andean margins of the Panthallassic ocean basin appear to have been the site of active subduction. This convergent system may have continued north into Southeast Asia, northern China, and southern Siberia. Continental reconstructions for the Late Cambrian, Late Ordovician, Late Silurian, and Late Devonian times are presented from a "Panthallassic" point-of -view. Paleomagnetic, biogeographic, and paleoclimatic evidence supporting three different Late Devonian reconstructions is reviewed.
  • Thumbnail Image
    Item
    Evolution of the Antarctic Continental Margins (Paleoceanographic Mapping Project Progress Report No. 31-1287)
    (Institute for Geophysics, 1987) Lawver, Lawrence A.; Royer, Jean-Yves; Sandwell, David T.; Scotese, Christopher R.
    With the exception of the Pacific facing margin of West Antarctica between Thurston Island and the tip of the Antarctic Peninsula, all of the continental margins of Antarctica are either rifted passive margins or sheared transform margins. The exception was a convergent margin where subduction was active from prior to the breakup of Gondwanaland until very recently. Starting in the southwestern Weddell Sea which rifted as part of a back -arc basin connected with back-arc spreading in the Rocas Verdes Basin of southern South America during the Middle to Late Jurassic ( -170 Ma), the continental margins of Antarctica seem to young clockwise. A sheared margin along the Explora Escarpment between 25°W and 10°W connected the southwestern Weddell Sea rifting with contemporaneous rifting in the Mozambique Basin. This resulted in a Middle Jurassic rifted passive margin along Dronning Maud Land. East of the Gunnerus Ridge at 35°E, Sri Lanka and India rifted off of Antarctica sometime between 129 Ma and 118 Ma. Rifting between Australia and Antarctica, stretching in the Ross Sea Embayment and rifting between the Campbell Plateau--Chatham Rise and Marie Byrd Land, all started about 95±5 Ma. The convergent margin on the Pacific margin of the Antarctic Peninsula stopped active subduction in the west at about 50 Ma, with the most recent subduction about 5 Ma off the South Shetland Islands. The only presently active continental margin on the Antarctic Continent is a short section of left lateral transform fault along the tip of the Antarctic Peninsula. Very young volcanism in the Ross Sea region may indicate that a new continental margin is in the initial stages of formation.
  • Thumbnail Image
    Item
    Evolution of the Eastern Indian Ocean since the Late Cretaceous Contraints from Geosat Altimetry (Paleoceanographic Mapping Project Progress Report No. 41-0888)
    (Institute for Geophysics, 1988) Royer, Jean-Yves; Sandwell, David
    We propose a new model for the tectonic evolution of the Eastern Indian Ocean from the Late Cretaceous to the present. Two types of data are used to improve previously-published reconstructions. First, reinterpreted seafloor magnetic anomalies, between Australia and Antarctica and in the Wharton basin, provide new constraints on spreading rates and the timing of major reorganizations. Second, vertical deflection profiles (i.e. horizontal gravity anomaly), derived from 22 repeat cycles of GEOSAT altimeter data, reveal the tectonic fabric associated with fracture zones. These new GEOSAT data provide tight constraints on paleo-spreading directions. For example, three prominent fracture zones can be traced from south of Tasmania to the George V Basin, Antarctica providing an important constraint on the relative motions of Australia and Antarctica through the Late Eocene. In addition, the GEOSAT profiles are used to locate the conjugate continental margins and continent-ocean boundaries of Australia and Antarctica, as well as the conjugate rifted margins of Kerguelen Plateau and Broken Ridge. Based on a compilation of magnetic anomaly data from the Crozet Basin, the Central Indian Basin, the Wharton Basin and the Australian-Antarctic Basin, ten plate tectonic reconstructions are proposed. Reconstructions at chrons 5 (11 Ma), 6 (21 Ma), 13 (36 Ma) and 18 (43 Ma) confirm that the Southeast Indian Ridge behaved as a single plate boundary since chron 18. The constraints from the GEOSAT data provide an improvement in the fit of the Kerguelen Plateau and the Broken Ridge at chron 20 (46 Ma). The opening of the Australian-Antarctic Basin from break-up to chron 24 requires a decoupling between the northern and southern provinces of the Kerguelen Plateau. Finally, the model for the relative motions of India, Australia and Antarctica is consistent with the emplacement of the Ninetyeast Ridge and the Kerguelen Plateau over a fixed hotspot.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Evolution of the Southwest Indian Ridge from the Late Cretaceous (Anomaly 34) to the Middle Eocene (Anomaly 20) (Paleoceanographic Mapping Project Progress Report No. 25-0987)
    (Institute for Geophysics, 1987) Royer, Jean-Yves; Patriat, Philippe; Bergh, Hugh W.; Scotese, Christopher R.
    The determination of the motion of Antarctica relative to Africa is particularly important when considering the breakup of Gondwana. Two models have been proposed that describe the pattern of seafloor spreading between Africa and Antarctica during the Late Cetaceous (starting at chron 34, 84 Ma) through to the Middle Eocene (chron 20, 46 Ma). In the flrst model, the motion of Antarctica relative to Africa can be simply described by a rotation about a single pole of rotation. In the second model, which we favor, the relative motion of Antarctica and Africa is more complex, and a major change in spreading direction between chron 32 (74 Ma) and chron 24 (56 Ma) times is required. In this paper we present 10 plate tectonic reconstructions of the Southwest Indian Ridge that were produced using a new compilation of magnetic, bathymetric, and satellite altimetry data, in combination with interactive computer graphics. These reconstructions illustrate that spreading directions started to change at chron 32 time (74 Ma). Between chrons 31 and 28 (69 to 64 Ma), spreading was very slow ( <1 cm/yr) and the direction of spreading changed from NE-SW to a more N-S direction. Between chrons 26 and 24 (61 to 56 Ma) the direction of spreading shifted back to a NE-SW orientation. These changes in spreading direction suggest that the present-day fracture zones in the area of the Prince Edward fracture zone are younger features (Eocene) than their lengths might imply. Our results also provide important constraints concerning the Mesozoic reconstructions of the Indian Ocean and the motion of South America relative to Antarctica prior to the Eocene.
  • Thumbnail Image
    Item
    Fit of the continents around the South Atlantic (Paleoceanographic Mapping Project Progress Report No. 22-0787)
    (Institute for Geophysics, 1987) Nuernberg, Dirk; Mueller, R. Dietmar; Scotese, Christopher R.
    All reconstructions proposed for the continents around the South Atlantic that require rigid plates result in substantial misfits either in the southern South Atlantic or in the equatorial Atlantic. Different solutions have been proposed to improve the fit of Africa and South America. We describe and discuss three different proposals: a model that assumes rigid African and South American plates, a model that requires an intraplate deformation zone within Africa, and a model that requires intraplate deformation within South America. Two recent plate tectonic models for opening of the South Atlantic are compared (Klitgord & Schouten 1986 and Pindell et al. in press) by calculating spreading rates and directions. Though the models that imply non-rigidity of the African and South American plates are an improvement, problems of misfit remain. In this paper we present two new reconstructions that result in an improved fit of Africa and South America. Additional constraints used in this study were derived from Seasat altimetry data. Seasat altimetry data were used to determine the directions of equatorial fracture zones which can be traced from the African to the South American margin. These fracture zones serve as tie-points for the predrift fit. Both models we propose require intraplate deformation within South America and Africa along a complex rift and strike-slip zone. Movements along these faults took place before or simultaneously with the breakup of the continents. These models eliminate gaps between the Guinea and Demarara Plateau and between the Falkland Plateau and South Africa, while avoiding large overlaps of continental margins or coastlines. Onshore geological and geophysical data, although being sparse for some regions, are consistent with the reconstructions we propose.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Opening of the Central North Atlantic: Revised Seafloor Spreading Isochrons and Tectonic Map from Geosat Data (Paleoceanographic Mapping Project Progress Report No. 39-0888)
    (Institute for Geophysics, 1988) Mueller, R. Dietmar; Scotese, Christopher R.; Sandwell, David T.
    Plate reconstructions for the opening of the Central and North Atlantic were made by combining Geosat altimetry and magnetic anomaly data. Geosat deflection of the vertical (horizontal gravity) data, which reflect the short wavelength basement topography of the ocean floor allowed us to construct a much improved map of fracture zones m the Central and North Atlantic. The fabric of prominent fracture zones, as interpreted from Geosat deflection of the vertical data, was utilized to constrain the fits of corresponding magnetic anomaly lineations by using an Evans and Sutherland 3-D graphics computer system. For example, we have used the trace of the Charlie-Gibbs Fracture Zone to better constrain the spreading history between the North American and Eurasian plate. Movements of smaller plates such as in the Canadian Arctic and the western Mediterranean were tied to the relative motion of the major plates by applying a hierarchical plate analysis technique. Our tectonic model served as a base to construct a self-consistent isochron chart of the Central and North Atlantic ocean floor.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Ordovician to Devonian Development of the Iapetus Ocean (Paleoceanographic Mapping Project Report No. 08-0185)
    (Institute for Geophysics, 1985) McKerrow, W. S.; Scotese, Christopher R.
  • Thumbnail Image
    Item
    Paleoceanographic Mapping Project (POMP): Research Goals, Methods, and Future Plans (Paleoceanographic Mapping Project Report No. 02-1184)
    (Institute for Geophysics, 1984) Scotese, Christopher R.; Lawver, Lawrence A.; Sclater, John G.; Sawyer, Dale
  • Thumbnail Image
    Item
    Paleomagnetic Constraints on the Fit of the Continents Around the Gulf of Mexico (Paleoceanographic Mapping Project Report No. 07-1285)
    (Institute for Geophysics, 1985) McCabe, Chad; Scotese, Christopher R.
    Paleomagnetic results from the Heldenberg and Trenton carbonates have been shown to be remagnetizations of Late Carboniferous or Early Permian age, and these results differ in a systematic way from other North American poles of the same age. In this paper we argue that these well-determined remagnetized limestone results may be more valid than previously published poles because all of the latter are from red bed studies in which the nature and origin of the magnetization are uncertain. A modified Pangea A@ with North America positioned according to the limestone poles has a looser fit in the critical Gulf of Mexico region, and is therefore more in accord with reconstructions based on geological data only.
  • Thumbnail Image
    Item
    Paleozoic Basemaps (Paleoceanographic Mapping Project Report No. 03-0984)
    (Institute for Geophysics, 1984) Scotese, Christopher R.