A fossil canyon, known as Gevaram canyon and postulated to be of submarine origin, exists in the southern coastal plain of Israel. This canyon was excavated in rocks of Middle Jurassic age which unconformably underlie strata of Early Cretaceous age.
The canyon runs in a northwest direction into the old Tethys through the Helez oil field and is at least 16 km long and 7 km wide. The canyon widens west of Helez. Maximum canyon depth is nearly 1,000 m; sediment fill consists mostly of dark-gray shale of the Gevaram Formation. Several sandy beds are present in the central part of the channel and limestone breccia derived from the wall rock fills the base.
After the canyon was filled and buried, clastic beds of the Helez Formation accumulated in the southwestern part of the area; gray shale of the Gevaram Formation accumulated in the northwest. An embayment formed in the Helez area as a result of local subsidence caused by compaction of the shale that filled the buried canyon. Through that embayment the source beds of the Gevaram Formation reached the area in which the reservoir beds of the Helez Formation were deposited. Contact between reservoir beds and source beds thus was established, resulting in accumulation of oil in the Helez field.