In 1972 Australia and Indonesia signed a series of seabed boundary treaties (Certain Seabed
Treaties)
4
which placed the seabed boundary approximately two thirds of the way to the
Indonesian (or West Timorese) and East Timorese coastline
5
. The primary basis for the
delimitation was the presence of the Timor Trough which under the concept of the natural
prolongation of the continental shelf
6
was agreed to constitute a geomorphological break in
the continental shelves of the two countries. Portugal, which had colonised East Timor in
1701, did not accept the agreed basis for delimitation, a position subsequently taken up by
Indonesia after its annexation of East Timor
7
. The resulting gap in the maritime boundary
became known as the Timor Gap.