Print this pageSequence Stratigraphy of Continental Strata in the Lower Paleozoic El Tibet Formation, Macizo de Floresta, Colombia
TELLEZ, G., and C. I. SOTELO
The El Tibet Formation, exposed in the central Floresta Massif, is the oldest unit of the Paleozoic sedimentary succession in the area and was accumulated in a sandy braided river.
Description and definition of the architectural elements allows to differentiate eight (8) lithofacies. The most typical facies are upward fining and thinning sequences ranging from medium- to coarse-grained sandstones, occasionally pebbly. Trough cross bedding, wavy lamination, ripple marks and horizontal lamination are present.
These lithofacies were grouped into seven (7) Facies Associations (FA) which are the product of midchannel migration of subaqueous dunes and ripples during low water stage (FA 1 and 2); linguoid or transverse bar migration formed during high-water episodes (FA 3); accretion of transverse bars during flood stages (FA 4); deposition during flash floods and high flow conditions (FA 5); and vertical aggradation of fine-grained sediments in the flood plains (FA 6). FA 7 was accumulated in a shallow marine environment.
The El Tibet Formation is composed of amalgamated channel deposits with minor associated fine-grained overbank material. These fining upward sequences are interpreted as a Lowstand Systems Tract overlying a sequence boundary unconformity. This Lowstand Systems Tract is composed of several higher order sequences, which systems tracts were recognized by the different degree of amalgamation and locally by the presence of marine sediments. The Alluvial transgressive Systems Tracts were deposited during periods of slow statigraphic base-level rise and reduced accommodation space, while the Alluvial High Stand Systems Tracts were accumulated when the accommodation space was higher due to rapid stratigraphic base-level rise.