Quench textures in altered spherules from the Cretaceous-Tertiary boundary layer at Agost and Caravaca, SE Spain

Ruiz, Francisca Martínez; Ortega-Huertas, M.; Palomo, I.; Acquafredda, Pasquale

doi:10.1016/s0037-0738(97)00057-2

Cited by 36 publications

(24 citation statements)

References 27 publications

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“…The thickness of the spherule bed at Bass River is consistent with the southeast contamination (Smit 1990;Martinez-Ruiz et al 1997). Thus, the spherule bed at Blake Nose records mainly the terrestrial material involved in the impact.…”

Section: Interpretations and Comparison With Other K-t Ejecta Depositssupporting

confidence: 59%

K-T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits

Martı́nez-Ruiz

Ortega-Huertas

Palomo-Delgado

et al. 2001

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The Cretaceous-Tertiary (K-T) boundary interval recovered by the ODP Leg 17 t at Site 1049 (Blake Nose, NWAtlantic) contains a thick (9-17 cm) spherule bed marking the boundary. The spherules are mainly perfect spheres with a lesser proportion of oval spherules. They usually range from 100 to 1000 lam. This bed represent the diagenetically altered impact ejecta from Chicxulub and further supports this structure as the site of the K-T impact. Mineralogical and geochemical investigations indicate that impact-generated glass was altered to smectite. Transmission electron microscopy observations revealed in some spherules that smectite is forming from a Si-rich or Ca-rich material, which could suggest a precursor similar to Haitian glasses. The variable thickness and the presence of some Cretaceous planktonic foraminifera and clasts of Cretaceous chalk suggest reworking of the ejecta material. However, the spherule bed confirms that a large volume of the Chicxulub ejecta material reached the Blake Nose Plateau.

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Section: Interpretations and Comparison With Other K-t Ejecta Depositssupporting

confidence: 59%

K-T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits

Martı́nez-Ruiz

Ortega-Huertas

Palomo-Delgado

et al. 2001

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“…Ni-rich iron oxides have also been reported by Soria et al (2001) for spherules of the La Sierrita area, as well as from "type 2" spherules from the K-T boundary clay (e.g., Doehne and Margolis 1990;Montanari 1991;Martínez-Ruíz et al 1997;Bauluz et al 2000;Claeys et al 2002). Ni-rich iron oxides have also been reported by Soria et al (2001) for spherules of the La Sierrita area, as well as from "type 2" spherules from the K-T boundary clay (e.g., Doehne and Margolis 1990;Montanari 1991;Martínez-Ruíz et al 1997;Bauluz et al 2000;Claeys et al 2002).…”

Section: Implications From Geochemical Phasesmentioning

confidence: 90%

“…Despite the fact that they are now pseudomorphically replaced by calcite or chlorite, their characteristic shapes may constrain their initial mineralogy. Such microliths have rarely been observed in "type 1" spherules from the K-T transition in other localities (e.g., Izett 1991;Bohor and Glass 1995), but are characteristic features of "type 2" spherules from the K-T boundary clay layer (e.g., Montanari 1991;Martínez-Ruíz et al 1997;Smit 1999). 10a, b EDS spectra of A 'metallic' and B 'sulfidic' Ni-, Corich inclusions in spherules and carbonates from La Sierrita (with 15 keV acceleration voltage).…”

Section: Implications From Petrological Characteristicsmentioning

confidence: 99%

“…This classifies them as "type 1" spherules that are interpreted to have originated as glassy fallout ("microtektites") from the impact ejecta curtain, but are now altered to clay minerals (e.g., smectite), or intermediate phases (e.g., palagonite), with schlieren-rich glass cores of andesitic composition (e.g., Izett 1991;Sigurdsson et al 1991;Bohor and Glass 1995;Premo et al 1995;Martínez-Ruíz et al 2002;Claeys et al 2002). In contrast, "type 2" spherules are solid, in part Ni-, Cr-spinel-bearing "microcrysts" of either K-feldspar, Fe-oxide, or smectite composition and are confined to the "red" siderophileand platinum group-element (PGE) enriched K-T boundary clay from the Atlantic, Pacific, and Tethyan realm (Smit and Klaver 1981;Doehne and Margolis 1990;Montanari 1991;Bohor and Glass 1995;Martínez-Ruíz et al 1997;Ortega-Huertas et al 1998;Bauluz et al 2000;Wdowiak et al 2001;Claeys et al 2002). These microcrysts and the boundary clay presumably formed by condensation from vaporized target-rock and meteoritic materials in the expanding fireball.…”

Section: Characteristics Of Spherule Depositsmentioning

confidence: 99%

“…Taking into account a potential contribution from mafic target rocks, it is remarkable that the petrological and mineralogical characteristics of the La Sierrita spherules and fragments bear an overall resemblance to the "type 2" spherules that are found in the K-T boundary clay layer in sections in the Atlantic, Pacific, and Tethyan realm (Doehne and Margolis 1990;Smit and Klaver 1981;Montanari 1991;Smit et al 1992a;Bohor and Glass 1995;Martínez-Ruíz et al 1997;Bauluz et al 2000;Claeys et al 2002;Verma et al 2002). These "type 2" spherules are compositionally highly variable and consist of hematite, goethite, magnetite, pyroxene, smectite, and K-feldspar, and frequently include Ni-, Cr-rich spinels.…”

Section: Implications From Geochemical Phasesmentioning

confidence: 99%

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Fe-rich and K-rich mafic spherules from slumped and channelized Chicxulub ejecta deposits in the northern La Sierrita area, NE Mexico

Schulte

Stinnesbeck

Stüben

et al. 2003

Int J Earth Sci (Geol Rundsch)

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Spherule deposits, commonly interpreted as ejecta from the Chicxulub impact at Yucatµn, Mexico, are present in many K-T (Cretaceous-Tertiary) sections. Geological mapping of the northern La Sierrita area, NE Mexico, revealed the presence of (1) multiple spherule deposits embedded in late Maastrichtian marls, which are folded or disaggregated (breccia-like). They are up to 6 m thick, locally present in two outcrop areas, and show limited lateral continuity. These deposits consist of mmcm sized spherical to drop-shaped vesiculated spherules, angular to filamentous (ejecta-) fragments and abundant carbonate. They are interpreted as primary ejecta fallout deposits that have been affected by subsequent local slumps-slides, liquefaction, and debris flows; welded components suggest an initial ground surge-like ejectadispersion mode.(2) A spherule deposit, 10-60 cm thick that constitutes the base of a channelized sand-siltstone deposit at, or close to, the K-T boundary and is characterized by wide lateral continuity. It is of similar petrologic composition to deposit (1), though slightly enriched in terrigeneous detritus, thus reflecting influx from proximal shelf areas. It is interpreted to result from debris flows and turbidite currents, though no size sorting and abrasion of ejecta has been observed. Petrological, mineralogical, and geochemical criteria suggest that ejecta components from both types of spherule deposits are similar and originated from the Chicxulub impact, with multiple deposits produced by subsequent remolding, reworking, and redeposition. Spherules and fragments have an Fe-(25-30 wt%), Al-, Mg-rich and Si-poor (<25 wt% SiO 2 ) composition, and are altered to chlorite and iron-oxides, though rare K-rich mafic glass (~50 wt% SiO 2 ; 5-8 wt% K) is also present. They contain Ti-, Fe-, K-rich schlieren, Fe-, Mg-rich globules, and rare m-sized metallic and sulfidic Ni-, Co-rich inclusions. Carbonate as clasts and within spherules and fragments shows textures indicative of quenching and/or liquid immiscibility. Although potential ejecta fractionation and alteration make accurate evaluation difficult, this composition suggests an ejecta origin mainly from mafic lithologies and carbonaceous sediments, in addition to a contribution from intermediate felsic rocks and the possibility of meteoritic contamination.

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The Stratigraphic Record of Impact Events: A Short Overview

Koeberl

Martı́nez-Ruiz

2003

Impact Studies

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Quench textures in altered spherules from the Cretaceous-Tertiary boundary layer at Agost and Caravaca, SE Spain

Cited by 36 publications

References 27 publications

K-T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits

K-T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits

Fe-rich and K-rich mafic spherules from slumped and channelized Chicxulub ejecta deposits in the northern La Sierrita area, NE Mexico

The Stratigraphic Record of Impact Events: A Short Overview

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