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dc.contributor.author
Gómez Peral, Lucia

dc.contributor.author
Poire, Daniel Gustavo

dc.contributor.author
Kaufman, Alan J.
dc.date.available
2023-01-11T11:54:33Z
dc.date.issued
2010
dc.identifier.citation
REE of Neoproterozoic phosphate concretions and their diagenetic implications: Tandilia System, Argentina; 18° International Sedimentological Congress; Mendoza; Argentina; 2010; 397-397
dc.identifier.isbn
978-987-96296-4-2
dc.identifier.uri
http://hdl.handle.net/11336/184256
dc.description.abstract
Two phosphogenetic events are recognized in the Neoproterozoic Tandi(ia System based on the preservation of concretionary phosphate P205 abundances ranging between 25 to 35%. The o(der of the two is atop the quartz-arkosic facies association of the Villa Mónica Formation (Gómez Peral et al., 2005). The age of this unit is until controversial since it was considered Tonian-Cryogenian for stromatolite assemblages (Poiré, 1993) and Ediacarian regarding acritarch assemblages (Gaucher et al., 2005). Further investigation on micropaleontology of the phosphate concretions is considered in order to assess the age of these rocks. The younger phosphate level is at the base of the Cerro Negro Formation (Ediacarian) in association with a widespread karstic surface. In both cases these phosphate concretionary levels are related to relative sea level fall probably as a result of g(aciations. Tota( REE contents in phosphate concretions range from 311 to 1010 ppm in the Villa Mónica Formation and from 290 to 1471 ppm in the Cerro Negro Formation. These values are comparab(e with averages reported for similarly-aged phosphogenetic events wor(dwide. Cerium is unusually enriched in the Villa Monica samples (Ce/La vary from 2.3 to 3.2), which may be attributed to either diagenetic alteration or an increase in the detrital component. All samples show a progressive depletion in REE abundance patterns, and positive Eu anomalies (ranging from 1. to 1.4). Eu anomalies may be considered as real since there is no positive correlation between Ba and Eu. The overall REE results suggest reducing conditions in deep marine environments, which may be re-lated to stratification of seawater in the Villa Monica basin. In the Cerro Negro samples Ce/La varies from 1.3 to 1.9, imp(ying little enrichment in Ce, and negative Ce anomalies (Ce/Ce*) range from -0.15 to -0.18; no Eu an-oma(ies are observed. These results are consistent with oxic sea water conditions in mixed platform (marls, silty sandstone - mud limestones) facies. Ce/Ce* are typically accepted as primary signatures if there is no correlation between LaN/SmN and when these ratios are above 0.35. In our sample set five samples show LaN/SmN slightly lower than 0.35. Furthermore, diagenetic processes may result in the correlation between Ce/Ce* and DyN/SmN, and positive correlation between Ce/Ce* and REE contents. These correlations do not appear and REE abund-ances likely reflect paleoseawater redox conditions. This study suggests that marine depositional conditions where phosphates accumulated were very different in these two discrete stratigraphic levels. The REE patterns from selected unaltered samples of the Villa Mónica Formation indicate a marine depositional environment with anoxic characteristics which could be linked with a stratified ocean probably related to the Cryogenian. On the other hand, phosphate concretions of the Cerro Negro Formation are associated with oxygenated seawater more characteristic of Later Ediacarian-Lower Cambrian oceans.
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
Asociación Argentina de Sedimentología
dc.rights
info:eu-repo/semantics/restrictedAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
REE
dc.subject
PHOSPHATE
dc.subject
NEOPROTEROZOIC
dc.subject
TANDILIA SYSTEM
dc.subject.classification
Geoquímica y Geofísica

dc.subject.classification
Ciencias de la Tierra y relacionadas con el Medio Ambiente

dc.subject.classification
CIENCIAS NATURALES Y EXACTAS

dc.title
REE of Neoproterozoic phosphate concretions and their diagenetic implications: Tandilia System, Argentina
dc.type
info:eu-repo/semantics/publishedVersion
dc.type
info:eu-repo/semantics/conferenceObject
dc.type
info:ar-repo/semantics/documento de conferencia
dc.date.updated
2023-01-10T19:20:58Z
dc.journal.pagination
397-397
dc.journal.pais
Argentina

dc.journal.ciudad
Mendoza
dc.description.fil
Fil: Gómez Peral, Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina
dc.description.fil
Fil: Poire, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina
dc.description.fil
Fil: Kaufman, Alan J.. University of Maryland; Estados Unidos
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/https://www.sedimentologists.org/isc
dc.conicet.rol
Autor

dc.conicet.rol
Autor

dc.conicet.rol
Autor

dc.coverage
Internacional
dc.type.subtype
Congreso
dc.description.nombreEvento
18° International Sedimentological Congress
dc.date.evento
2010-09-26
dc.description.ciudadEvento
Mendoza
dc.description.paisEvento
Argentina

dc.type.publicacion
Book
dc.description.institucionOrganizadora
International Association of Sedimentology
dc.source.libro
Abstracts of the 18° International Sedimentological Congress
dc.date.eventoHasta
2010-10-01
dc.type
Congreso
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