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Christopher L. Johnson1,
Evan K. Franseen2,
Robert H. Goldstein3
(1) University of Kansas, Lawrence, KS
(2) Kansas Geological Survey, Lawrence, KS
(3) University Of Kansas, Lawrence, KS
Abstract: Interplay of relative sea level and variable paleotopography on geometry and facies in temperate-water carbonates: An example from the Upper Miocene, Southeastern Spain
Outcrops in southeastern Spain expose Upper Miocene (Tortonian) temperate-water carbonates that formed on the flanks of a volcanic archipelago. Volcanic basement was subaerially exposed and eroded resulting in variable substrate paleoslopes and paleovalley systems that combined with relative sea level to control facies distribution and stratal geometries.
The study area around Cerro de
Los Lobos reveals two depositional sequences (DS1A, DS1B) predominantly composed
of heterozoan packstones and planktonic foraminiferal wackestones. DS1A
carbonates (35 m thick) were deposited during an overall relative sea-level
rise and fall of ~30-35 m. DS1B strata (140 m thick) were deposited during an
overall relative sea-level rise of at least 140 m. DS1B comprises approximately
11 fining-upward cycles (1-20 m thick) that reflect higher frequency relative
sea-level fluctuations. Bases of cycles are characterized by sharp contacts and
skeletal packstones, some with laterally discontinuous, m-scale trough
cross-bedding, suggesting relative sea-level falls. Overlying deposits consist
of debris flows and coarse-grained turbidites that grade upward into
hemipelagic, foraminiferal wackestones, suggesting relative sea-level rises. The
11th cycle is dominated by laterally continuous trough cross-beds suggesting an
overall relative shallowing at the end of DS1B. DS1B stratal geometries and
facies patterns indicate paleovalleys (
350 m wide; apparent slopes of valley walls
19 ) were important for localizing
sediment on sloping substrates. Variations in geometry (drape, sidelap, and
lens) respond to changes in location of the sediment source.
Detailed three-dimensional information on controls, stratal geometries and facies patterns presented here provide predictive reservoir models for temperate-water carbonates in areas of variable paleoslope.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana