Russian Journal of Earth Sciences
Vol. 4, No. 4, August 2002
Strontium isotopic evidence for supercontinental breakup
and formation in the Riphean: Western margin of the Siberian craton
E. M. Khabarov, V. A. Ponomarchuk, and I. P. Morozova
Abstract
Sr isotopic composition in carbonate rocks of the Baikit anteclise and
Yenisei Ridge, western margin of the Siberian craton, has been analyzed. These
rocks were formed between 1500-1450 and 850 Ma. Carbonate deposits of the
Baikit anteclise are featured by low Sr isotopic ratios that increase gradually
form 0.70404 to 0.7052 up the stratigraphy. Riphean carbonate rocks of the
Yenisei Ridge exhibit a wide scatter of
87Sr/86Sr (0.7050-0.7095 or higher).
High Sr isotopic ratios are coupled chiefly with considerable postdepositional
changes of the rocks. Comparing
87Sr/86Sr trends and rocks assemblages formed
at different positions of the relative sea-level shows that lows on the
87Sr/86Sr
curve correlate well with transgressions and relative sea level highstands, while
high Sr isotopic ratios correspond to sea-level drops.