PALEOMAGNETIC RECONSTRUCTION OF A DIAPIR EMPLACEMENT - A CASE-STUDY FROM SEDOM DIAPIR, THE DEAD-SEA RIFT

Reconstructing the emplacement path of a diapiric sequence is relative ly complex, in part because the stratigraphic (top versus bottom) sens e of the sequence can be obscured by the complex structure. Paleomagne tic study of the diapiric sequence may reveal simultaneously three cha racteristics of it: (1) the stratigraphic sense, (2) the three-dimensi onal rotation path of the tilted sequence, and (3) the magnetic polari ty of the sequence. We apply paleomagnetism to reconstruct the emplace ment path of the Sedom diapir in the Dead Sea Rift, Israel. This appli cation resolves the ambiguity regarding the geometrical orientation of the thickest intrarift stratigraphic section (2 km) exposed in the De ad Sea region. We here report the natural remanent magnetization for 1 72 oriented samples (mainly dolomite and siltstone) from seven localit ies in the steeply inclined beds of the Sedom diapir. A fold test, as well as other field and laboratory tests, shows that the characteristi c remanent magnetization (ChRM) component of the rocks was acquired be fore the tilting of the Sedom sequence, whereas the low-coercivity mag netic component of probably chemical remanent magnetization origin was acquired after the tilting. This low-coercivity (secondary) component , likely acquired in the Brunhes Normal chron, records up to 40 degree s young counterclockwise rotation about a vertical axis. The ChRM and secondary components (together with the bedding plane) were restored t o their expected (original) position by rotating them about horizontal , vertical, or inclined axes to get the complete three-dimensional rot ation path. The resulting structure of the southern Sedom diapir is co mposed of a thin western ''salt wall'' that is juxtaposed against a th ick eastern salt wall. In the northern part of the mountain apparently only the thick eastern salt wall is exposed.