Lower Jurassic felsic diatreme volcanism recognized in central Patagonia as evidence of along-strike rift segmentation

The early Jurassic volcanism of Central Patagonia covers an extensive area 50,000 km2 where the volcanic deposits occur as isolated systems. records form elongated belt in which composition, depositional and genetic features, show several differences along with its distribution. Cañadón Chileno Complex (CCHC), located Río Negro province, provides opportunity to evaluate improve knowledge about Lower stratigraphy regional setting Patagonia. Based on field laboratory data developed present work, 22 lithofacies were recognized grouped into eight facies associations. continental sedimentary environments include alluvial fan (FA 1), ephemeral 2), braided fluvial 3), plains, or over banks 4), lacustrine 9). On other hand, pyroclastic separated according currents involved during deposition; fall-out, dilute, density 5, FA 6, 7). Effusive andesitic feeders lava-flows 8) also recognized. stratigraphic obtained work allow proposing existence two felsic diatreme volcanoes CCHC - described here Southern Northern Zone-, a local subsided area, represented by asymmetrical basin. Seven units (Units a, b, c, d, e, f, g: unit (a) represents initial stage sedimentation recorded throughout entire Complex. Unit (b) upper facies, Zone Complex, debris flows are interbedded massive lapilli-tuff deposits. (c) consists lavas feeder dikes, (d) welded lapilli tuff interpreted growth system. evolves similarly intra-diatreme (e). (f) consisting effusive extended lava flows. Finally, deep system is installed (unit g) that includes shallow intercalations Also, new geochronological (U-Pb zircon age 188 ± 3 Ma) was determined confirm reinforce correlation criteria between different areas Patagonia, indicating synchronous silica-rich calderas Garamilla Formation well large Lonco Trapial southward CCHC. changes described, connected N-S rift segment limited E-W transfer fault systems continuity strike-slip structures La Esperanza area.