Stratigraphy Middle Magdalena Valley

1 stratigraphy

1.1 first sequence
1.2 second sequence
1.3 third sequence

stratigraphy

tectonic , stratigraphic timeline of middle magdalena basin, colombia.

the stratigraphy of middle magdalena basin can divided 3 sequences separated angular unconformities. basement of these sequences pre-mesozoic metaclastics , sediments exposed on surface of central cordillera result of deformation , uplift. geologic basement @ 15 kilometres (9.3 mi) deep, faulted sections shifted approximately 10 kilometres (6.2 mi) in depth. unconformity separates basement first sequences indicates approximate time rifting began.

first sequence

the first sequence deposited in jurassic during rifting caused initial formation of basin. jurassic formation called girón group consists of siltstones , rhyolitic tuffs. during period, basin experienced granitic plutonism along western margins. jurassic-cretaceous angular unconformity, separating first , second sequence, representative of post-rift boundary.

second sequence

the middle sequence represents formations deposited throughout cretaceous , paleocene. oldest formations in sequence tambor , los santos formations. conglomerates , sandstones indicate continental fluvial depositional environment. in cretaceous, sea level began rise , formed shallow marine environment siltstone , shale deposits of cumbre formation. sea level continued rise throughout middle cretaceous when tablazo , salto limestones , simití shales deposited. la luna formation represents maximum flooding surface deep marine deposits of limestone, chert, , shale. sea level began fall, returning environment shallow marine deposition of umir formation of shales , sandstones. finally, paleocene saw deposition of lisama formation, consisting of deltaic mudstones , sandstones. entire middle sequence indicates marine megacycle consisting of 5 transgressive-regressive cycles. angular unconformity between second , third sequences result of erosion accretion of western ranges.

third sequence

the final sequence represents deposition tertiary present day. within sequence, there 3 subsequences result of deformation , uplift of central , eastern ranges. first subsequence consists of chorro group la paz , esmeraldas formations , chuspas group mugrosa , colorado formations, deposited during eocene oligocene. these groups consist of fluvial sandstones, mudstones, siltstones, , shales, , result of erosion in central ranges. second subsequence miocene real group, consisting of fluvial sandstones , conglomerates. similar real group, final subsequence pliocene mesa formation, composed of sandstones , conglomerates deposited due eastern ranges uplift. uppermost sedimentary rocks of basin pleistocene alluvial fan deposits, overlain holocene sediments of magdalena river.