| Ocean: | Marginal basin, South East Asia |
| Spreading center type: | Backarc basin spreading ridge/Intra-oceanic spreading center |
| Time of cessation: | Ca. 26 Ma, chron C8r (Gaina and Müller, 2007) |
| Subsequent active spreading center: | None in immediate area |
Relatively few studies have investigated this region in recent years, with many regional studies dating from the 1970s. Gaina and Müller (2007) proposed that chron C8 could be identified either side of the Kilsgaard Trough, although the trend of the trough structure is somewhat inconsistent with that of the magnetic anomalies west of 147 E. In the western extent of the trough, it appears to cut across crust of older age to the south of the youngest crust identified by magnetic isochrons. The trough structure is thought to be approximately the same age as the Caroline Trough that is situated to the west. The basins have somewhat different tectonic fabrics and it has been proposed that the Kilsgaard Trough spreading ridge ceased after the spreading center in the West Caroline Basin (Gaina and Müller, 2007).
A prominent fault, cross-cutting the neighbouring Eauripik Ridge, is described by Erlandson et al. (1976), who observe that this ridge is formed on thickened crust. Gaina and Müller (2007), propose that the fault post-dates formation of the ocean crust in both the East and West Caroline Basins and considered that the Eauripik Ridge may have been a leaky transform fault.
Convergence at the borders of the Caroline Basin is believed to have led to accretion of the Caroline Arc, onto Melanesia, at ca. 25 Ma that reuslted in cessation of spreading in the backarc basin (Gaina and Müller, 2007).
The morphology of the Kilsgaard Trough, that is shown by Erlandson et al. (1976) in their Figure 6, is broadly similar to a number of other extinct ridge axial troughs observed elsewhere./p>
Erlandson, D.L., Orwig, T.L., Kiilsgaard, G., Mussells, J.H. and Kroenke, L.W., 1976, Tectonic interpretations of the East Caroline and Lyra Basins from reflection-profiling investigations, Geological Society Of America Bulletin, v. 87, p. 453–462.
Gaina, C. and Müller, R. D. 2007, Cenozoic tectonic and depth/age evolution of the Indonesian gateway and associated back-arc basins, Earth-Science Reviews, v. 83, no. 3-4, p. 177–203.
