Cyclic
Sedimentation From the Cenomanian/Turonian
of
Duque-Botero,
Fabian1, Florentin J.M-R. Maurrasse2, Mihaela Carmen Melinte3 (1) Chevron ETC,
Houston, TX (2) Florida International University, Miami, FL (3) National
Institute of Marine Geology and Geoecology - Geomar,
Sediments of the Indidura
Formation in the
Identification of calcareous nannofossils zones CC-10 to CC-13 allowed the determination
of sedimentation rates of 6.2 and 10.1 cm/ka that were used to transform
thickness to calendar years. Findings indicate that variability at the field
scale correlates with Milankovicth precession cycle
of about 23.000 years. At the microscopic scale analysis reveals that laminae register much shorter-term climatic variability
that occurred at periodicities of 10-15 year pulses similar to present day
solar Schwabe cycles.
We interpret changes as indicated by
organic geochemistry to be the result of fluctuating cyanobacterial
productivity, which increased during peak precession periods with low sediment
supply and high recycling of nutrients. A similar situation is inferred at millimetric scale, were nutrient variability that was
controlled by periodic increased in pluviosity at the
decadal scale, which in turn generated enhanced/decreased productivity
conditions where calcifying cyanobacterial bloomed.
Present work shows that climatic
variability at solar scale during peak precession cycles was the dominant
factor in the accumulation of this organic rich sequence and points to the
importance of cyanobacterial derived organic matter
as potential contributors to the generation hydrocarbons rocks in the
sedimentary record.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California