Tertiary spreading geometries north of Iceland

Continental separation between Greenland and NW Europe occurred around the Paleocene-Eocene boundary (Chron 24R), the final part of the Atlantic Ocean to open. On the basis of spreading history, this relatively young oceanic basin can be divided into northern, central and southern segments, separated by fracture zones.

The northern segment (north of the Jan Mayen Fracture Zone) and the southern segment (south of Iceland) have much in common: a relatively simple spreading history with linear COBs and a single, central spreading axis. However, the central segment, between Iceland and the Jan Mayen Fracture Zone, exhibits a much more complex spreading history involving an active spreading centre (the Kolbeinsey Ridge), an extinct spreading centre (the Aegir Ridge), and an intervening microcontinent (the Jan Mayen microcontinent), which was formerly part of the East Greenland margin. Uncertainties in the duration and geometry of spreading on each ridge, and the dimensions of the Jan Mayen microcontinent, have led to conflicting hypotheses for tectonic evolution. Furthermore, continental break-up in the northern North Atlantic was associated with the eruption and intrusion of large volumes of magma related to the Iceland plume. The voluminous magmatic rocks tend to mask the location of the COB across transitional regions that may be well in excess of 100 km across. This uncertainty in positioning of the COB can have serious consequences for continental fits.

The central segment of oceanic crust is adjacent to a number of prospective hydrocarbon basins. Accurate palinspastic reconstructions provide a regional framework for understanding tectonic evolution, and are an essential tool in evaluating regional hydrocarbon potential. For example, using high-resolution reconstructions, it should be possible to determine sediment transport paths for individual sediment bodies, to correlate specific structural elements, and to predict the likely timing and stress patterns associated with structural development. We present the results of a recent study aimed at constraining the spreading history of the central segment in which geophysical datasets were manipulated in a geographic information system (GIS), with the aim of accurately locating the COBs and picking the magnetic anomalies. These data have then been used to define plate rotations in a GIS-compatible reconstruction program.