@article{fdi:010061302,
  title = {{S}edimentology and geomorphology of the deposits from the {A}ugust 2006 pyroclastic density currents at {T}ungurahua volcano, {E}cuador},
  author = {{D}ouillet, {G}. {A}. and {T}sang-{H}in-{S}un, {E}. and {K}ueppers, {U}. and {L}etort, {J}. and {P}acheco, {D}. {A}. and {G}oldstein, {F}. and {V}on {A}ulock, {F}. and {L}avallee, {Y}. and {H}anson, {J}. {B}. and {B}ustillos, {J}. and {R}obin, {C}laude and {R}amon, {P}. and {H}all, {M}. and {D}ingwell, {D}. {B}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he deposits of the pyroclastic density currents from the {A}ugust 2006 eruption of {T}ungurahua show three facies associations depending on the topographic setting: the massive, proximal cross-stratified, and distal cross-stratified facies. (1) {T}he massive facies is confined to valleys on the slopes of the volcano. {I}t contains clasts of >1 m diameter to fine ash material, is massive, and interpreted as deposited from dense pyroclastic flows. {I}ts surface can exhibit lobes and levees covered with disk-shaped and vesicular large clasts. {T}hese fragile large clasts must have rafted at the surface of the flows all along the path in order to be preserved, and thus imply a sharp density boundary near the surface of these flows. (2) {T}he proximal cross-stratified facies is exposed on valley overbanks on the upper part of the volcano and contains both massive coarse-grained layers and cross-stratified ash and lapilli bedsets. {I}t is interpreted as deposited from (a) dense pyroclastic flows that overflowed the gentle ridges of valleys of the upper part of the volcano and (b) dilute pyroclastic density currents created from the dense flows by the entrainment of air on the steep upper flanks. (3) {T}he distal cross-stratified facies outcrops as spatially limited, isolated, and wedge-shaped bodies of cross-stratified ash deposits located downstream of cliffs on valleys overbanks. {I}t contains numerous aggrading dune bedforms, whose crest orientations reveal parental flow directions. {A} downstream decrease in the size of the dune bedforms, together with a downstream fining trend in the grain size distribution are observed on a 100-m scale. {T}his facies is interpreted to have been deposited from dilute pyroclastic density currents with basal tractional boundary layers. {W}e suggest that the parental flows were produced from the dense flows by entrainment of air at cliffs, and that these diluted currents might rapidly deposit through "pneumatic jumps". {T}hree modes are present in the grain size distribution of all samples independently of the facies, which further supports the interpretation that all three facies derive from the same initial flows. {T}his study emphasizes the influence of topography on small volume pyroclastic density currents, and the importance of flow transformation and flow-stripping processes.},
  keywords = {{T}ungurahua ; {P}yroclastic density currents ; {F}low stripping ; {S}edimentary ; wedge ; {H}ydraulic jump ; {EQUATEUR}},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {75},
  numero = {11},
  pages = {765},
  ISSN = {0258-8900},
  year = {2013},
  DOI = {10.1007/s00445-013-0765-7},
  URL = {https://www.documentation.ird.fr/hor/fdi:010061302},
}