Late Cenozoic volcaniclastic deposits, Andean foredeep, Colombia

Research Article| April 01, 1976 Late Cenozoic volcaniclastic deposits, Andean foredeep, Colombia FRANKLYN B. VAN HOUTEN FRANKLYN B. VAN HOUTEN 1Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08540 Search for other works by this author on: GSW Google Scholar Author and Article Information FRANKLYN B. VAN HOUTEN 1Department of Geological and Geophysical Sciences, Princeton University, Princeton, New Jersey 08540 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (4): 481–495. https://doi.org/10.1130/0016-7606(1976)87<481:LCVDAF>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation FRANKLYN B. VAN HOUTEN; Late Cenozoic volcaniclastic deposits, Andean foredeep, Colombia. GSA Bulletin 1976;; 87 (4): 481–495. doi: https://doi.org/10.1130/0016-7606(1976)87<481:LCVDAF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Volcaniclastic deposits preserved in the upper Magdalena Valley, Colombia, were derived from stratovolcanoes on Cordillera Central during and after the late Cenozoic Andean orogeny. Andesitic lava clasts and suites of mineral grains, commonly mixed with plutonic and metamorphic rock fragments, predominate in proximal debris flows and in torrential channel lenses; reworked dacitic pyroclastic material is more common in distal debris flows, sheeted overbank sands, and flood-plain muds.Earliest Colombian volcanism is recorded by montmorillonite in the mid-Cenozoic La Cira Formation (1,000 m). During early phases of Andean orogeny in middle and late Miocene time (20 to 10 m.y. ago), abundant volcanic clasts and volcanic mineral grains accumulated in coarse channel and flood-plain sediments of the Honda Group (3,000 m), along with a few thin sheets of reworked pyroclastic debris. The overlying conglomeratic Neiva Formation (200 m) records renewed uplift and a fresh supply of lava. In latest Miocene time (8 to 9 m.y. ago) the climax of explosive activity swamped the Andean foredeep with debris that accumulated on coalescing fans of the Gigante Formation (750 m).About 7 to 5 m.y. ago, the final Andean orogenic phase deformed both Cordillera Central and its foredeep. Subsequent excavation of the uplifted eastern lowland was interrupted at least ten times by local incursions of volcanic detritus 10 to 75 m thick. These deposits include polymictic debris flows and torrential sediments that filled valleys and formed large fans, and reworked pumiceous debris concentrated in fluvial valley fill and in debris flows that spread widely across the Magdalena lowland. Older deposits are preserved in high-level mesas, valley terraces, and deeply dissected fans; younger deposits form low, relatively undissected fans and inner terraces along major streams. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.