Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events

Two meter-scale pyroclastic levels are interbedded within the early Miocene succession of the Estancia 25 de Mayo (Patagoniense transgression) and Santa Cruz formations in the foreland Austral (or Magallanes) Basin, Argentina. The Lower Pyroclastic Level (LPL) is a tabular body interbedded within of...

Descripción completa

Guardado en:
Detalles Bibliográficos
Autores principales: Cuitiño, José Ignacio, Scasso, Roberto Adrian
Publicado: 2013
Materias:
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00370738_v289_n_p194_Cuitino
http://hdl.handle.net/20.500.12110/paper_00370738_v289_n_p194_Cuitino
Aporte de:
id paper:paper_00370738_v289_n_p194_Cuitino
record_format dspace
spelling paper:paper_00370738_v289_n_p194_Cuitino2023-06-08T15:02:13Z Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events Cuitiño, José Ignacio Scasso, Roberto Adrian Explosive volcanism Fluvial deposits Hyperpycnal flows Patagonia Pyroclastic deposits Explosive volcanism Fluvial deposits Hyperpycnal flows Patagonia Pyroclastic deposits Debris Fallout Laminating Quartz Sedimentology Sediments Volcanoes Deposits batholith explosive volcanism fluvial deposit foreland basin geoaccumulation grain size marine sediment Miocene plagioclase pyroclastic deposit pyroclastic flow quartz sediment thickness sediment transport tuff Patagonia Two meter-scale pyroclastic levels are interbedded within the early Miocene succession of the Estancia 25 de Mayo (Patagoniense transgression) and Santa Cruz formations in the foreland Austral (or Magallanes) Basin, Argentina. The Lower Pyroclastic Level (LPL) is a tabular body interbedded within offshore marine deposits, laterally continuous for 30. km and varying in thickness from few centimeters to around 4. m. Grain-size grades from coarse to extremely fine ash with upward-fining along with a northeastern-fining trends. Structureless fine to very fine tuffs dominate and rare parallel laminations are the only tractive sedimentary structures. The Upper Pyroclastic Level (UPL) lies within low energy fluvial deposits and is laterally discontinuous, and it is composed by lenticular bodies reaching a maximum of 15. m thick and 100. m wide, with a concave-up base and a plane top. Grain-size range is similar to the LPL but it coarsens upward. The lower portion of the UPL shows parallel lamination, current ripple lamination and mud drapes with large pumice lapilli and plant debris, whereas the upper portion shows parallel lamination and trough cross-stratification. Both pyroclastic levels are composed mainly of pumice grains and glass shards with minor proportions of quartz and plagioclase crystals and lithic fragments. The LPL shows no mixing with epiclastic material whereas the UPL shows an upward increase in epiclastic material, and an upward increment in the scale of cross-bedding.The large thickness in relation to the possible emission center and the content of plant debris of the LPL does not suggest a direct, submarine, ash-fallout origin. The LPL is interpreted as a deposit of hyperpycnal-flows generated at the coastal zone when tephra-laden rivers plunged into the ocean. Large amounts of well preserved plant debris support the hypothesis of a terrestrial source of the sediments. The UPL is entirely composed of tractive deposits, so an ash fallout origin is disregarded. This, together with the lenticular shape and the alluvial plain origin of the encasing sediments, suggests accumulation within fluvial channels. Cycles of upper-flow-regime parallel lamination, current-ripple lamination and mud drapes at the lower portion, suggest short-lived turbulent flows that initially filled semi-abandoned channels. They were followed by sheet floods and channel reactivation, expressed by large-scale cross-bedding. The low degree of particle mixing observed in both levels is explained by the inability of streams to erode the substrate as they are suddenly over-saturated with pyroclastic sediments during and after the eruption. The grain-size distribution of the LPL and geochemical data indicate a contemporaneous volcanic source located to the west/southwest in the Andean ranges, where the South Patagonian Batholith is presently located. © 2013 Elsevier B.V. Fil:Cuitiño, J.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Scasso, R.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2013 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00370738_v289_n_p194_Cuitino http://hdl.handle.net/20.500.12110/paper_00370738_v289_n_p194_Cuitino
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Debris
Fallout
Laminating
Quartz
Sedimentology
Sediments
Volcanoes
Deposits
batholith
explosive volcanism
fluvial deposit
foreland basin
geoaccumulation
grain size
marine sediment
Miocene
plagioclase
pyroclastic deposit
pyroclastic flow
quartz
sediment thickness
sediment transport
tuff
Patagonia
spellingShingle Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Debris
Fallout
Laminating
Quartz
Sedimentology
Sediments
Volcanoes
Deposits
batholith
explosive volcanism
fluvial deposit
foreland basin
geoaccumulation
grain size
marine sediment
Miocene
plagioclase
pyroclastic deposit
pyroclastic flow
quartz
sediment thickness
sediment transport
tuff
Patagonia
Cuitiño, José Ignacio
Scasso, Roberto Adrian
Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
topic_facet Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Explosive volcanism
Fluvial deposits
Hyperpycnal flows
Patagonia
Pyroclastic deposits
Debris
Fallout
Laminating
Quartz
Sedimentology
Sediments
Volcanoes
Deposits
batholith
explosive volcanism
fluvial deposit
foreland basin
geoaccumulation
grain size
marine sediment
Miocene
plagioclase
pyroclastic deposit
pyroclastic flow
quartz
sediment thickness
sediment transport
tuff
Patagonia
description Two meter-scale pyroclastic levels are interbedded within the early Miocene succession of the Estancia 25 de Mayo (Patagoniense transgression) and Santa Cruz formations in the foreland Austral (or Magallanes) Basin, Argentina. The Lower Pyroclastic Level (LPL) is a tabular body interbedded within offshore marine deposits, laterally continuous for 30. km and varying in thickness from few centimeters to around 4. m. Grain-size grades from coarse to extremely fine ash with upward-fining along with a northeastern-fining trends. Structureless fine to very fine tuffs dominate and rare parallel laminations are the only tractive sedimentary structures. The Upper Pyroclastic Level (UPL) lies within low energy fluvial deposits and is laterally discontinuous, and it is composed by lenticular bodies reaching a maximum of 15. m thick and 100. m wide, with a concave-up base and a plane top. Grain-size range is similar to the LPL but it coarsens upward. The lower portion of the UPL shows parallel lamination, current ripple lamination and mud drapes with large pumice lapilli and plant debris, whereas the upper portion shows parallel lamination and trough cross-stratification. Both pyroclastic levels are composed mainly of pumice grains and glass shards with minor proportions of quartz and plagioclase crystals and lithic fragments. The LPL shows no mixing with epiclastic material whereas the UPL shows an upward increase in epiclastic material, and an upward increment in the scale of cross-bedding.The large thickness in relation to the possible emission center and the content of plant debris of the LPL does not suggest a direct, submarine, ash-fallout origin. The LPL is interpreted as a deposit of hyperpycnal-flows generated at the coastal zone when tephra-laden rivers plunged into the ocean. Large amounts of well preserved plant debris support the hypothesis of a terrestrial source of the sediments. The UPL is entirely composed of tractive deposits, so an ash fallout origin is disregarded. This, together with the lenticular shape and the alluvial plain origin of the encasing sediments, suggests accumulation within fluvial channels. Cycles of upper-flow-regime parallel lamination, current-ripple lamination and mud drapes at the lower portion, suggest short-lived turbulent flows that initially filled semi-abandoned channels. They were followed by sheet floods and channel reactivation, expressed by large-scale cross-bedding. The low degree of particle mixing observed in both levels is explained by the inability of streams to erode the substrate as they are suddenly over-saturated with pyroclastic sediments during and after the eruption. The grain-size distribution of the LPL and geochemical data indicate a contemporaneous volcanic source located to the west/southwest in the Andean ranges, where the South Patagonian Batholith is presently located. © 2013 Elsevier B.V.
author Cuitiño, José Ignacio
Scasso, Roberto Adrian
author_facet Cuitiño, José Ignacio
Scasso, Roberto Adrian
author_sort Cuitiño, José Ignacio
title Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
title_short Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
title_full Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
title_fullStr Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
title_full_unstemmed Reworked pyroclastic beds in the early Miocene of Patagonia: Reaction in response to high sediment supply during explosive volcanic events
title_sort reworked pyroclastic beds in the early miocene of patagonia: reaction in response to high sediment supply during explosive volcanic events
publishDate 2013
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00370738_v289_n_p194_Cuitino
http://hdl.handle.net/20.500.12110/paper_00370738_v289_n_p194_Cuitino
work_keys_str_mv AT cuitinojoseignacio reworkedpyroclasticbedsintheearlymioceneofpatagoniareactioninresponsetohighsedimentsupplyduringexplosivevolcanicevents
AT scassorobertoadrian reworkedpyroclasticbedsintheearlymioceneofpatagoniareactioninresponsetohighsedimentsupplyduringexplosivevolcanicevents
_version_ 1768546245363630080