Open AccessClockwise and anticlockwise rotation of Viti Levu, Fiji—in relation to the tectonic development of the North and the South Fiji Basin
Author(s) -
Inokuchi Hiroo,
Yaskawa Katsumi,
Rodda Peter
Publication year - 1992
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1992.tb00869.x
Subject(s) - clockwise , geology , paleomagnetism , paleontology , structural basin , apparent polar wander , tectonics , neogene , stage (stratigraphy) , rotation (mathematics) , geometry , mathematics
SUMMARY Samples for palaeomagnetic study were collected from 40 sites in Viti Levu, Fiji. Reliable palaeomagnetic directions were obtained from 22 sites after magnetic cleaning. These data cover the age between late Eocene to Pliocene. Geological study indicates that Viti Levu can be structurally divided into three stages; stage 1 (late Eocene to early Oligocene), stage 2 (early to middle Miocene) and stage 3 (late Miocene to Pliocene). The mean palaeomagnetic direction ( D, I ) for each stage is (‐10d̀, ‐48d̀) in stage 1, (‐64d̀, ‐28d̀) in stage 2 and (‐32d̀ ‐45d̀) in stage 3, respectively. Expected directions of the geomagnetic field in the past were calculated from the Australian apparent polar wander path (APWP) and were subtracted from the obtained palaeomagnetic directions in geological sequence. Then, the tectonic movement in and around the island of Viti Levu with respect to the Australian Plate was estimated for post‐Eocene time. The following conclusions were reached. (1) A clockwise rotation of about 45d̀ took place during Oligocene, (2) an anticlockwise rotation of about 75d̀ had occurred since the end of the middle Miocene time, and (3) the Euler poles of these rotations were situated in or near Fiji. A tectonic history of the Fiji region since late Eocene, which can explain the episodes of clockwise and anticlockwise rotations of Viti Levu, is as follows: clockwise rotational movement in Oligocene was closely related to the formation of the South Fiji Basin and anticlockwise rotational movement since the end of middle Miocene was closely related to the formation of the North Fiji Basin. The clockwise rotation of Viti Levu was accompanied by fan‐shaped spreading in the northern half of the South Fiji Basin, in which a system, ridge‐ridge‐ridge (R‐R‐R) triple junction of plates, was involved. The subsequent anticlockwise rotation of Viti Levu can be explained as ‘ball‐bearing’ rotation associated by antithetical transform faults accompanied with the spreading of the North Fiji Basin.