Abstract

A comparison of structures formed since the Pliocene during Australia-Banda Are collision with structures hi the central British Isles provides insights into early tectonic events and later structures formed along the Laurentian margin of the Iapetus Ocean between Ordovician and Devonian tunes. In particular, the timing of ophiolite emplacement, incorporation of a volcanic are into a continental margin and early stages hi nappe formation can be recognized by comparing seismic reflectors and mapped geological structures hi both regions. In this comparison the Midland Valley of Scotland is interpreted as a compressed and composite volcanic are, formed hi two stages as the result of are reversal and becoming more mafic than adjacent blocks which were formed from accretionary prisms.

Uniformitarian principles are used to interpret geochemical processes and tectonic events throughout the Phanerozoic and have also been used to interpret events in the Proterozoic and Archaean (e.g. Taylor & McLennan 1995). The Tonga-Kermadec, Aleutian, Andean and Banda-Sunda ares are often cited as present-day analogues of ancient convergent plate boundaries. Similar logic motivated BIRPS to acquire two deep seismic reflection profiles across the currently active Australia-Banda are collision zone to the east of Timor (Figs 1 & 2a) in order to provide a better understanding of the tectonic events represented by structures that formed along the margin of Laurentia during the closure of the Iapetus Ocean c. 450 Ma (Fig. 2) and that are observed in the crust of the British Isles today.

The Banda Arcs mark the site of subduction of

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