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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 (^bull 350 m wide; apparent slopes of valley walls ^bull 19^bull ) 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