Use of a Computer-based Dataset to Constrain Opening of the Labrador Sea

The PLATES project at the University of Texas at Austin has compiled an extensive database which includes published marine magnetic anomalies, plate lineations derived from satellite gravity data, published paleomagnetic data, and geological and structural data. We will show a PC-based plate reconstruction program to illustrate the tectonics of the North Atlantic - Arctic region for the Mesozoic to present. Recent aerogeophysical data from the Eurasian Basin as well as magnetic anomaly identifications from the Norwegian-Greenland Sea are used with published magnetic anomaly picks from the Labrador Sea augmented with magnetic anomaly picks from the Geological Survey of Canada Open File report 3125 published in 1996. With the exception of Rowley and Lottes (1988), it has been assumed that seafloor spreading in the Labrador Sea ended by Chron 13 or 33.9 Ma. Rowley and Lottes (1988) concluded that seafloor spreading had to have continued until 25 Ma or Chron 7 time to avoid an unacceptable overlap of Northeast Greenland with Svalbard. Our computer based work support the conclusions of Rowley and Lottes (1988). We have redated some of the older magnetic anomalies in the Labrador Sea as well as identified anomalies younger than 35 Ma. During the initial opening of the Norwegian-Greenland Sea, seafloor spreading in the Labrador Sea switched from a nearly east-west spreading from breakup in Late Cretaceous to the beginning of the Eocene, to NNE-SSW spreading which left almost transform motion along what had been the spreading center from the end of Chron 25 (55.9 Ma) to the beginning of Chron 22 (49.7 Ma). From Middle Eocene to the end of seafloor spreading in the Labrador Sea in the Late Oligocene, the seafloor spreading rate was very slow, perhaps as slow as 3 mm/yr half-rate with a direction of NE-SW. Opening in the Eurasian Basin began almost 20 million years before the opening in the Norwegian-Greenland Sea. Initial opening was very slow but allows a longitudinally fixed Lomonosov Ridge to be assumed. Northward motion of Greenland produced not only the Eurekan orogeny on Ellesmere Island but some shortening of the Eurasian Basin seafloor prior to 25 Ma. Rowley, D.B. and Lottes, A.L., 1988. Plate-kinematic reconstructions of the North Atlantic and Arctic: Late Jurassic to Present. Tectonophysics 155, 73-120.