Print this pageGlacioeustatic Fluctuation: The Mechanism Linking 
Stable
Isotope Events and Sequence Stratigraphy From the Early Oligocene to Middle
Miocene
Vitor Abreu and Geoffrey Haddad
One of the most difficult challenges of sequence stratigraphy is the
establishment of synchronism between events observed in widely-separated basins.
Problems arise because the resolution of the best stratigraphic methods is not
good enough to establish the synchronism of similar-aged events on a global
scale. Unless a common mechanism affecting global eustasy is assumed, such as
variations in the ice volume, there is no a priori reason to expect
that sequences of similar age in widely-separated basins are indeed synchronous.
The stable oxygen isotope composition of marine carbonates is a proxy for sea
level which has been underutilized in sequence stratigraphy. Identification of
isotope events is based on d18O data from DSDP and ODP sites 522,
529, 563, 608, and 747 drilled in the Atlantic and Indian oceans. These records
were used by Miller et al (1991) to define Oligocene and Miocene oxygen
isotope zones. In addition, we present isotope data from PETROBAS Well A drilled
in the Campos Basin (Brazil).
Ages of isotope events correspond well with the ages of sequence boundaries
and maximum flooding surfaces identified by Haq et al (1988), Vakarcs
et al (1995), and Hardenbol et al (1995). Because of the good
correlation between the isotope
and sequence stratigraphic records, we reconfirm
that ice-volume change is the common mechanism driving sea- level fluctuations
from the Oligocene to present.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California