Bianucci, Giovanni

Bosio, Giulia

Celma, Claudio Di

Gariboldi, Karen

Gioncada, Anna

Malinverno, Elisa

Urbina, Mario

Villa, Igor Maria

The upper Miocene Pisco Formation (Peru) represents a world-known fossil Lagerstätte containing abundant and exceptionally well-preserved marine vertebrates. A detailed chronostratigraphic reconstruction is indispensable to study this fossil record and to understand the evolution of marine vertebrates. Recent work (Bianucci et al., 2016; Di Celma et al., 2016; Gariboldi et al., in press) in the area of the western Ica River Valley defined a detailed
chronostratigraphic framework for the Pisco Formation, containing all the fossil vertebrates observed in the area.
Such chronostratigraphic framework, based on new 40Ar/39Ar ages on biotite from tephra layers integrated with diatom biostratigraphy, implements previous scattered radiometric data (Brand et al., 2011; Esperante et al., 2015). Tephra layers representing primary air-fall deposition of volcanic ash from the Peruvian Andes volcanoes are very frequent in the Pisco Formation. Several of them do not show evidence of reworking or bioturbation. Due to their regional dispersal and to their geologically instantaneous deposition (Lowe, 2011), they provide the opportunity not only to date specific layers, when suitable for radiometric age determination, but also to correlate different localities, through the chemical fingerprinting of tephra.
We collected more than 200 tephra layers from different localities in the Ica Desert along six measured stratigraphic sections. Based on the estimated stratigraphic position, we analyzed specific tephra layers through petrographic characterization, glass shard morphology, electron probe microanalyses of glass shards and, where present, biotite crystals. Despite some difficulties encountered, such as similar magma or mineral composition, local weathering, lack of record due to marine current transport and change in depositional environments among different localities,
the correspondence of the obtained data allowed to verify correlations that were supposed during field work and to trace tephra layers from distant outcrop localities, allowing to refine the chronostratigraphy of the Pisco Formation in the western Ica River Valley

GIONCADA, ANNA

GARIBOLDI, KAREN

BIANUCCI, GIOVANNI

Archivio della Ricerca - Università di Pisa

Geophysical Research AbstractsVol. 19, EGU2017-13433, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.The potential of chemical fingerprinting of tephra for stratigraphiccorrelations in the fossil Lagerstätte of the Pisco Formation (Peru)Giulia Bosio (1), Anna Gioncada (2), Elisa Malinverno (1), Igor Maria Villa (1,3), Claudio Di Celma (4), KarenGariboldi (2), Mario Urbina (5), and Giovanni Bianucci (2)(1) Dipartimento di Scienze dell’Ambiente e del Territorio e di Scienze della Terra, Università di Milano-Bicocca, Milan, Italy(g.bosio1@campus.unimib.it; elisa.malinverno@unimib.it; igor.villa@unimib.it), (2) Dipartimento di Scienze della Terra,Università di Pisa, Pisa, Italy (anna.gioncada@unipi.it; karengariboldi@gmail.com; bianucci@dst.unipi.it), (3) Institut fürGeologie, Universität Bern, Bern, Switzerland (igor.villa@geo.unibe.ch), (4) Scuola di Scienze e Tecnologie, Università diCamerino, Camerino, Italy (claudio.dicelma@unicam.it), (5) Departamento de Paleontología de Vertebrados, Museo deHistoria Natural, Universidad Nacional Mayor de San Marcos, Lima, Peru (mariourbina01@hotmail.com)The upper Miocene Pisco Formation (Peru) represents a world-known fossil Lagerstätte containing abundant andexceptionally well-preserved marine vertebrates. A detailed chronostratigraphic reconstruction is indispensable tostudy this fossil record and to understand the evolution of marine vertebrates. Recent work (Bianucci et al., 2016;Di Celma et al., 2016; Gariboldi et al., in press) in the area of the western Ica River Valley defined a detailedchronostratigraphic framework for the Pisco Formation, containing all the fossil vertebrates observed in the area.Such chronostratigraphic framework, based on new 40Ar/39Ar ages on biotite from tephra layers integrated withdiatom biostratigraphy, implements previous scattered radiometric data (Brand et al., 2011; Esperante et al., 2015).Tephra layers representing primary air-fall deposition of volcanic ash from the Peruvian Andes volcanoes are veryfrequent in the Pisco Formation. Several of them do not show evidence of reworking or bioturbation. Due to theirregional dispersal and to their geologically instantaneous deposition (Lowe, 2011), they provide the opportunitynot only to date specific layers, when suitable for radiometric age determination, but also to correlate differentlocalities, through the chemical fingerprinting of tephra.We collected more than 200 tephra layers from different localities in the Ica Desert along six measured stratigraphicsections. Based on the estimated stratigraphic position, we analyzed specific tephra layers through petrographiccharacterization, glass shard morphology, electron probe microanalyses of glass shards and, where present, biotitecrystals. Despite some difficulties encountered, such as similar magma or mineral composition, local weathering,lack of record due to marine current transport and change in depositional environments among different localities,the correspondence of the obtained data allowed to verify correlations that were supposed during field work and totrace tephra layers from distant outcrop localities, allowing to refine the chronostratigraphy of the Pisco Formationin the western Ica River Valley.Bianucci G. et al (2016) Journal of Maps, 12: 1037–1046.Brand L.R. et al (2011) J. South Am. Earth Sci., 31: 414–425.Di Celma C. et al (2016) Journal of Maps, 12: 1020-1028.Esperante R. et al. (2015) Palaeogeography, Palaeoclimatology, Palaeoecology, 417: 337–370.Gariboldi K. et al (in press) Newsletters on Stratigraphy.Lowe D.J. (2011) Quaternary Geochronology, 6: 107-153.

English

The potential of chemical fingerprinting of tephra for stratigraphic correlations in the fossil Lagerstätte of the Pisco Formation (Peru)

The potential of chemical fingerprinting of tephra for stratigraphic correlations in the fossil Lagerstätte of the Pisco Formation (Peru)

The potential of chemical fingerprinting of tephra for stratigraphic correlations in the fossil Lagerstätte of the Pisco Formation (Peru)

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