@article{fdi:010070095,
  title = {{C}omplex remanent magnetization in the {K}izilkaya ignimbrite (central {A}natolia ): implication for paleomagnetic directions},
  author = {{A}gro, {A}. and {Z}anella, {E}. and {L}e {P}ennec, {J}ean-{L}uc and {T}emel, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{P}yroclastic flow deposits, known as ash-flow tuffs or ignimbrites, are invaluable materials for paleomagnetic studies, with many applications for geological and tectonic purposes. {H}owever, little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy. {I}n this work we investigate this issue by concentrating on the {K}izilkaya ignimbrite, the youngest large-volume unit of the {N}eogene ignimbrite sequence of the {C}entral {A}natolian {V}olcanic {P}rovince in {T}urkey, bringing evidence of significant magnetic heterogeneities in ignimbrite deposits (magnetic mineralogy, susceptibility, magnetic remanence, coercivity, etc.) and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data. {S}ix sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite. {I}sothermal remanence measurements point to low-{T}i titanomagnetite as the main magnetic carrier at all sites; at some sites, the occurrence of oxidized {T}i-magnetite and hematite is disclosed. {T}he bulk susceptibility (k(m)) decreases vertically at two out of six sections: its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base. {I}n most cases, low k(m) values relate to high coercivity of remanence ({B}-{CR}) values, which range from 25 to >400 m{T}, and to low {S}-ratios (measured at 03 {T}) between 0.28 and 0.99. {T}hese data point to the occurrence of oxidized magnetic phases. {W}e therefore consider the k(m) parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized {T}i-magnetite and hematite within the deposit. {T}he characteristic remanent magnetization is determined after stepwise thermal and {AF} demagnetization and clearly isolated by principal component analysis at most sites. {F}or these sites, the site mean paleomagnetic direction is consistent with data from the literature. {A}t a few other sites, the remanence is more complex: the direction moves along a great circle during demagnetization and no stable end-point is reached. {T}he occurrence of oxidized {T}i-magnetite or hematite as well as two remanence components with overlapping coercivity and blocking temperature spectra suggest that the {K}izilkaya ignimbrite acquired first a thermal remanent magnetization and then, during the final cooling or a short time later, a secondary remanent magnetization component which is interpreted as a {CRM} acquired during post-emplacement devitrification processes. {N}otwithstanding the {K}izilkaya ignimbrite is a single cooling unit, its magnetic properties suffered substantial variations laterally and vertically within the deposit. {T}he {K}izilkaya case shows that thick pyroclastic deposits should be sampled using a stratigraphic approach, at different sites and different stratigraphic heights at each individual sampling location, otherwise, under-sampling may significantly affect the paleomagnetic results. {W}hen sampling is performed on a short duration or on very poorly preserved deposits we recommend drilling the lower-central portion in the most strongly welded and devitrified fades. {S}uch sampling strategy avoids complications arising from the potential presence of a pervasive secondary {CRM} masking the original {C}h{RM}.},
  keywords = {{I}gnimbrite ; {M}agnetic remanence ; {K}izilkaya ; {C}appadocia ; {TURQUIE} ; {ANATOLIE}},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {336},
  numero = {},
  pages = {68--80},
  ISSN = {0377-0273},
  year = {2017},
  DOI = {10.1016/j.jvolgeores.2017.02.007},
  URL = {https://www.documentation.ird.fr/hor/fdi:010070095},
}