THE CRETACEOUS-TERTIARY BOUNDARY IN SOUTHERN LOW-LATITUDE REGIONS - PRELIMINARY-STUDY IN PERNAMBUCO, NORTHEASTERN BRAZIL

被引：37

作者：

ALBERTAO, GA ^{[1
]}

KOUTSOUKOS, EAM ^{[1
]}

REGALI, MPS ^{[1
]}

ATTREP, M ^{[1
]}

MARTINS, PP ^{[1
]}

机构：

[1] PETROBRAS DESUD,BR-2791350 MACAE,RJ,BRAZIL

来源：

TERRA NOVA | 1994年 / 6卷 / 04期

关键词：

D O I：

10.1111/j.1365-3121.1994.tb00509.x

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

A preliminary integrated study of a Cretaceous-Tertiary (K/T) boundary section in Pernambuco, northeastern Brazil, provides evidence for an extraterrestrial bolide impact in the earliest Danian. A non-graded, nodular carbonate mudstone/wackestone bed is interpreted as a slump or a mud Flow deposit, induced by a tsunami event or by a gravity mass movement during a sea-level lowstand, the former possibly generated by the K/T boundary Yucatan impact. This bed overlies marlstones deposited in an upper bathyal environment and marks the top of the Cretaceous. Nearly all known latest Maastrichtian planktonic foraminifera are recovered from the Cretaceous strata. Iridium shows a marked peak in a thin hemipelagic claystone layer, about 75 cm above the K/T boundary, deposited in a middle to deep neritic environment. The claystone overlies alternating beds of fine-grained limestones and marlstones and a 50 cm-thick graded bioclastic packstone, which rests upon a marly limestone breccia of the lowermost Danian. Abundant reworked Cretaceous and rare lowermost Danian microfossils (e.g. E. edita, E. eobulloides, E. fringa, G. irregularis, P. eugubina, P. cf. pseudobulloides, W. claytonensis and W. hornerstownensis) have been recovered from these strata. These lowermost Danian beds record the sudden appearance of abundant shock-metamorphosed quartz grains, with several sets of intersecting deformation lamellae and microtektite-like microspherules. This suggests that these deposits were formed by an additional tsunami caused by a second impact event in the earliest Danian, near or at the boundary between the Palaeocene P alpha and P 1a foraminiferal zones. Impact-derived material has not been found in the uppermost Cretaceous beds.

引用

页码：366 / 375

页数：10

共 56 条

[1]

Aigner T., Storm Depositional Systems, Lecture Notes in Earth Sciences, 3, (1985)

[2]

Albertao G.A., Abordagem interdisciplinar e epistemológica sobre as evidências do limite Cretáceo‐Terciário, com base em leituras efetuadas no registro sedimentar das bacias da costa leste brasileira, (1992)

[3]

Alvarez L.W., Alvarez W., Asaro F., Michel H.V., Extraterrestrial cause for the Cretaceous‐Tertiary extinction, Science, 208, pp. 1095-1108, (1980)

[4]

Alvarez W., Alvarez L.W., Asaro F., Michel H.V., The end of the Cretaceous: sharp boundary or gradual transition, Science, 223, pp. 1183-1186, (1984)

[5]

Alvarez W., Smit J., Lowrie W., Asaro F., Margolis S.V., Claeys P., Kastner M., Hildebrand A.R., Proximal impact deposits at the Cretaceous‐Tertiary boundary in the Gulf of Mexico: A restudy of DSDP Leg 77 Sites 536 and 540, Geology, 20, pp. 697-700, (1992)

[6]

Ashraf A.R., Stinnesbeck W., Pollen und Sporen an der Kreide‐Tertiárgrenze im Staate Pernambuco, NE Brasilien, Palaeont. Abt. B, 208, pp. 39-51, (1988)

[7]

Baadsgaard H., Lerbekmo J.F., Mac-Dougall I., A radiometric age for the Cretaceous‐Tertiary boundary based upon K‐Ar, Rb‐Sr, and U‐Pb ages of bentonites from Alberta, Saskatchewan, and Montana, Can. J. Earth Sci., 25, pp. 1088-1097, (1988)

[8]

Bohor B.F., Shock‐induced microdeformations in quartz and other mineralogical indications of an impact event at the Cretaceous‐Tertiary boundary, Tectonophysics, 171, 1-4, pp. 359-372, (1990)

[9]

Bohor B.F., Foord D.D., Modreski P.J., Triplehorn D.M., Mineralogic evidence of an impact event at the Cretaceous‐Tertiary boundary, Science, 224, pp. 867-869, (1984)

[10]

Bohor B.F., Modreski P.J., Foord E.E., Shocked quartz in the Cretaceous‐Tertiary boundary clay: evidence for a global distribution, Science, 236, pp. 705-709, (1987)

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