@article{fdi:010042681,
  title = {{P}aleomagnetism, magnetic fabric, and {A}r-40/{A}r-39 dating of {P}liocene and {Q}uaternary ignimbrites in the {A}requipa area, southern {P}eru},
  author = {{P}aquereau-{L}ebti, {P}. and {F}ornari, {M}ichel and {R}operch, {P}ierrick and {T}houret, {J}. {C}. and {M}acedo, {O}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A}r-40/{A}r-39 ages and paleomagnetic correlations using characteristic remanent magnetizations ({C}h{RM}) show that two main ignimbrite sheets were deposited at 4.86 +/- 0.07 {M}a ({L}a {J}oya {I}gnimbrite: {LJI}) and at 1.63 +/- 0.07 {M}a ({A}requipa {A}irport {I}gnimbrite: {AAI}) in the {A}requipa area, southern {P}eru. {T}he {AAI} is a 20-100 m-thick ignimbrite that fills in the {A}requipa depression to the west of the city of {A}requipa. {T}he {AAI} is made up of two cooling units: an underlying white unit and an overlying weakly consolidated pink unit. {R}adiometric data provide the same age for the two units. {A}s both units record exactly the same well-defined paleomagnetic direction (16 sites in the white unit of {AAI}: {D}ec=173.7; {I}nc=31.2; alpha 95=0.7; k=2749; and 10 sites in the pink unit of {AAI}; {D}ec=173.6; {I}nc=30.3; alpha 95=1.2; k=1634), showing no evidence of secular variation, the time gap between emplacement of the two units is unlikely to exceed a few years. {T}he > 50 m thick well-consolidated white underlying unit of the {A}requipa airport ignimbrite provides a very specific magnetic zonation with low magnetic susceptibilities, high coercivities and unblocking temperatures of {NRM} above 580 degrees {C} indicating a {T}i-poor titanohematite signature. {T}he {A}nisotropy of {M}agnetic {S}usceptibility ({AMS}) is strongly enhanced in this layer with anisotropy values up to 1.25. {T}he fabric delineated by {AMS} was not recognized neither in the field nor in thin sections, because most of the {AAI} consists in a massive and isotrope deposit with no visible textural fabric. {P}umices deformation due to welding is only observed at the base of the thickest sections. {AMS} within the {AAI} ignimbrite show a very well defined pattern of apparent imbrications correlated to the paleotopography, with planes of foliation and lineation dipping often at more than 20 degrees toward the expected vent, buried beneath the {N}evado {C}hachani volcanic complex. {I}n contrast with the relatively small extent of the thick {AAI}, the {L}a {J}oya ignimbrite covers large areas from the {A}ltipano down the {P}iedmont. {T}i-poor titanomagnetites are the dominant magnetic carriers and {AMS} values are generally lower than 1.05. {M}agnetic foliations are sub horizontal and lineations directions are scattered in the {LJI}. {T}he {AMS} fabrics are probably controlled by post-depositional compaction and welding of the deposit rather than transport dynamics.},
  keywords = {{I}gnimbrite ; {P}aleomagnetism ; {A}r-40/ar-39 age ; {A}ms ; {M}agnetic mineralogy ; {E}mplacement mechanisms ; {P}eru},
  booktitle = {},
  journal = {{B}ulletin of {V}olcanology},
  volume = {70},
  numero = {8},
  pages = {977--997},
  ISSN = {0258-8900},
  year = {2008},
  DOI = {10.1007/s00445-007-0181-y},
  URL = {https://www.documentation.ird.fr/hor/fdi:010042681},
}