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Geochemical comparison of K-T boundaries from the northern and southern hemispheres
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K - A r A G E OF K A R A I M P A O T S T R U C T U R E : K V I D E N C E F O R ITS LINK W I T H C R E T A C E O U S T E R T I A R Y ( K / T ) EVENT
-YIJ.A.SBI;KOLUKOv, E.M.KOL~SNIKOV, M.A.NAZAaO¥, D , D , I ~ D J ~ O ¥ ~ 4 M.Z.KO~IJA (Vernadeky Chemistry, USSR).
InsZ. of G e o c h e m . a n d A n a l y t . M o s c o w State U n i v e r s i t y , M o s c o w ,
G e o c h e m i c a l a n o m a l i e s d i s c o v e r e d at K / T b o u n d a r y w e r e i n t e r p r e t e d as a r e s u l t of a g i a n t i m p a c t e ~ e n t w h i c h c o u l d be r e s p o n s i b l e for the C r e t a c e o u s m a s s e x t i n c t i o n . It w a s s u g g e s t e d that the K / T p r o j e c t i l e i m p a c t e d the o c e a n ~rust. H o w e v e r a p r e s e n ce of s h o c k e d q u a r t z in the K / T s e d i m e n t s , p o i n t s to the f o r m a t i o n of a c o n t e m p o r a r y c r a t e r an a c o n t i n e n t . The K a r a (60 km) and U s t - K a r a (25 km) i m p a c t c r a t e r s (USSR) h a v e b e e n p r o p o s e d as the p o s s i b l e [ / T c o n t i n e n tal c r a t e r s . The g o a l of the s t u d y is to d e t e r m i n e K - A r age of the c r a t e r s and to est i m a t e % h e i r l i n k w i t h the K / T event. It w a s s h o w n by s t u d y that m o s t of ~ e K a r a i m p a c t i t e s c o n t a i n s a ~ e x c e s s of ~ A r d u e to i n c o m p l e t e o u t g a s i n g o r a g a s c ~ @ t u re d u r i n g i m p a c t m e l t i n g . The t r a p p e d Ar c o n t e n t d e p e n d s on a t h e r m a l h i s t o r y and a d e g r e e of s e c o n d a r y a l t e r a t i o n of i m p a c t i t e s . K / A t i s o c h r o n e a g e of K a r a i m p a c t i t e s w a s f o u n d to be 6 6 . 1 t 0 . 8 (16) M.Y. that c o i n c i d e s e x a c t l y w i t h the age of the K / T b o u n dary. A t the u s u a l c r a t e r i n g r a t e there s h o u l d not h a v e b e e n two ( d i f f e r e n t in age) c o n t i n e n t a l c r a t e r s b i g g e r than 60 km for 3,2 M.Y. (26 e r r o r at 1~he age e s t i m a t e ) . It s u g g e s t s that the K a r a c r a t e r s c o u l d be form e d by f r a g m e n t s of the K / T p r o j e c t i l e , d i s r u p t e d b e f o r e the c o l l i s i o n .
GEOCIIEMICAL COMPARISON OF K-T BOUNDARIES FROM TIlE NORTIIERN AND SOUTIIERN IIEM1SPI1ERES M. TREDOIIX, BTH. VERHAOEN, R L HART, MJ. DE WIT, C.B. SMITH, K. PERCH-NIELSEN and /.PF. SELLSCHOP. ~Vits-CSIR Schonland Research Centre for Nuclear Sciences, University of the Witwatersrand, 2050 South Africa) The extinctions which mark the Cretaceous-Tertiary
(K-T) boundary have been
ascribed to a meteorue impact. The major evidence quoted in support of this model is the enrichment of I; (a plamium-group element (PGE)) in the boundary clays. Closely spaced (era-scale) traverses through the K-T boundary at Stevns Klint (Denmark). Woodside Creek (New Zealand) and Richards Bay (South Africa) have been subjected to a trace clement
andstable
isotope investigation.
Intercomparison between these
data sets, ~ d co.elation with the broad data-base available in the literature, indicale that the chemistry of the boundary clays is not constant. Variations are more common than similarities; for example, the absolute values of Ir (and the olher POE) differ by more than an order of magnitude on a global scale and the choodrite normalized POE patterns of Sterns Klint are not hke those of Woodside Creek. The differences in POE patterns are difficult to explain by secondary alteration of a once-cbemicaIlyhomogeneous Ia) or, especially for elernents of such dubious crustal mobility, as Os and Ir. This fact, coupled to the recent observation that hot-spot volcanism (eg. Kilauea. Hawaii) can produce aerosols that are very enriched in siderophile eTements. (eg. It, Au. Ni. Co) lead the authors to suggest that the possible terrestrial component of the siderophi[e element ennchment in tile K-T clays has not been adequately identified. It is suggested that an extended period of Late Cretaceous volcanism can offer a satisfactory explanadon of tile K-T geochemical anomaly. This model would probably be more consistent with the observed ~tepwise, or gradual, palaeontological changes across this boundary., than tile "instant" cauastrophe predicted by the impact theory.
METEORITIC NOBLE CAS IN K-T BOUNDARY N. TAKAOKA and Y. MIURA (Dept. Earth Sci.~ Yamasata Univ. and Dept. Mineral. Geol. Sci., Yamaguchi Univ., Japan) We report result of noble gas analysis of clay sample from the K-T boundary at Steavns Klint in Denmark. The clay sample(SK-2-4) of 51.67 g was etched by 6N-HCI and conc. HF. After HF-etching for 2 days, the sample was washed by distilled water and dried. The weight decreased to 16.38 g by HF-etching. In the acid etching, we never heated nor used any oxidizing chemicals because heating releases loosely trapped gases and the oxidizing chemicals removes carbonaceous matters. Part(5.08 g) of residues was heated in a Ta furnace to melt. Techniques of noble gas analysis have been given elsewhere[l]. A large excess of He-3 (R=69Ra) and a slight depletion of Ne-20 were found relative to atmosph. ratios. High He ratios in deep-sea sediments and diamonds are accompanied by high Ne ratios[2,3]. A high He ratio in volcanic rocks is due to cosmogenic He[4,5]. The high He and low Ne ratios in this work are incompatible with the isotopic signature for deep-sea sediments and diamonds. The sampling site at Steavns Klint is on a sea shore and was underground in the past time. Therefore, cosmic-rays could not intrude the K-T boundary. These suggest the existence of a noble gas component different from that identified in terr. matters mentioned above: The cosmogenic or/and planetary-type gas. The present result suggests that the sediments from the K-T boundary at Stearns Klint contain matters of meteoritic origin. Ref. [i] Takaoka,N.(1976) Mass Spectr.24, 73-86. [2] Amari,S.,Ozima,M.(1986)Terra cognita 6, 102. [3] Honda,M. et ai.(1986) Terra cognita 6, 104. [4] Kurz,M.(1986) Geochim.Cosmochim.Acta 5--0,28552862. [5] Craig,H.,Podera,R.(1986) Proc. Natl. Acad. Sci. USA 83, 1970-1974
ISOTOPIC(St, Nd) AND CHEMICALVARIATIONSACROSSTHE K-T BOUNDARY. L.TURPIN, R. ROCCHIA,M. RENARD and D. BOCLET.
(CEA/IRDI, SEAINBat. 391, CEN Saclay, 91191 Gif sur Yvatte Codex, France). Samplescoilestedin threesites,8idart(S.W. France),StevnsKlint (Danemark) and Raton Basin (USA) have been analysedfor Sr and Nd isotoperatiosend trace elements.At Bidant,about 10m below the bounder,/,excursionsof the 87,Sr1865r ratiobetween 0.70805 and 0.70789 are observed,contrastingwith the smooth, regularincrease of 87Sr186Sr from -217m (Upper Campaoian). At Stavns KIint,
excursions are also observed, but at e lesser extent, and the 875r/86Sr ratio at the boundary is higher than at Bidart At Raton Basin, supposed to have been an inner sea during the K-T transition, the 875r/865r of the leacheles are rather constant at ~0.7095. 143Nd/144Nd ratios of the leaching residues are always slightly more radiogenic in the Ir-rlch layers, even in the continental lignite from Raton Basin, but no Important variations of the 67Sr/a6Sr ratios appear. Th-Hf-Ta and Ni-Or-Co abundance ratio determinations in these three sites, and also including additional eemples from Canavaca (Spain) emphasize (1) the constancy of terrigenous inputs from continental crust (2) transition element pattern evolution similar to those observed in metalliferous sediments and far from chondritic average. All these results lead to the following conclusions: ( I ) About 1 Ma before the K-T transition, the kinetic equilibrium which regulates the 87Sr/86Sr of sea water suffered dramatic perturbations: this correlates with ammonite extinctions (2) These perturbations do not onrretate between sites: this is probably due to the fact that the time scale ( 1 Me) is lower than the time residence of Sr in the oceans (3) Although 145Nd/ 144Nd present a minor, but systematic change at the boundary, the bulk geochemistry of terrigenous inputs does not present significant changes. No geochemical evidence unequivocally favouring either e terrestrial or an extra-terrestrial event can be deduced from our results, but the duration of the perturbation could well have beenat least I Me.
K - A r A G E OF K A R A I M P A O T S T R U C T U R E : K V I D E N C E F O R ITS LINK W I T H C R E T A C E O U S T E R T I A R Y ( K / T ) EVENT
-YIJ.A.SBI;KOLUKOv, E.M.KOL~SNIKOV, M.A.NAZAaO¥, D , D , I ~ D J ~ O ¥ ~ 4 M.Z.KO~IJA (Vernadeky Chemistry, USSR).
InsZ. of G e o c h e m . a n d A n a l y t . M o s c o w State U n i v e r s i t y , M o s c o w ,
G e o c h e m i c a l a n o m a l i e s d i s c o v e r e d at K / T b o u n d a r y w e r e i n t e r p r e t e d as a r e s u l t of a g i a n t i m p a c t e ~ e n t w h i c h c o u l d be r e s p o n s i b l e for the C r e t a c e o u s m a s s e x t i n c t i o n . It w a s s u g g e s t e d that the K / T p r o j e c t i l e i m p a c t e d the o c e a n ~rust. H o w e v e r a p r e s e n ce of s h o c k e d q u a r t z in the K / T s e d i m e n t s , p o i n t s to the f o r m a t i o n of a c o n t e m p o r a r y c r a t e r an a c o n t i n e n t . The K a r a (60 km) and U s t - K a r a (25 km) i m p a c t c r a t e r s (USSR) h a v e b e e n p r o p o s e d as the p o s s i b l e [ / T c o n t i n e n tal c r a t e r s . The g o a l of the s t u d y is to d e t e r m i n e K - A r age of the c r a t e r s and to est i m a t e % h e i r l i n k w i t h the K / T event. It w a s s h o w n by s t u d y that m o s t of ~ e K a r a i m p a c t i t e s c o n t a i n s a ~ e x c e s s of ~ A r d u e to i n c o m p l e t e o u t g a s i n g o r a g a s c ~ @ t u re d u r i n g i m p a c t m e l t i n g . The t r a p p e d Ar c o n t e n t d e p e n d s on a t h e r m a l h i s t o r y and a d e g r e e of s e c o n d a r y a l t e r a t i o n of i m p a c t i t e s . K / A t i s o c h r o n e a g e of K a r a i m p a c t i t e s w a s f o u n d to be 6 6 . 1 t 0 . 8 (16) M.Y. that c o i n c i d e s e x a c t l y w i t h the age of the K / T b o u n dary. A t the u s u a l c r a t e r i n g r a t e there s h o u l d not h a v e b e e n two ( d i f f e r e n t in age) c o n t i n e n t a l c r a t e r s b i g g e r than 60 km for 3,2 M.Y. (26 e r r o r at 1~he age e s t i m a t e ) . It s u g g e s t s that the K a r a c r a t e r s c o u l d be form e d by f r a g m e n t s of the K / T p r o j e c t i l e , d i s r u p t e d b e f o r e the c o l l i s i o n .
GEOCIIEMICAL COMPARISON OF K-T BOUNDARIES FROM TIlE NORTIIERN AND SOUTIIERN IIEM1SPI1ERES M. TREDOIIX, BTH. VERHAOEN, R L HART, MJ. DE WIT, C.B. SMITH, K. PERCH-NIELSEN and /.PF. SELLSCHOP. ~Vits-CSIR Schonland Research Centre for Nuclear Sciences, University of the Witwatersrand, 2050 South Africa) The extinctions which mark the Cretaceous-Tertiary
(K-T) boundary have been
ascribed to a meteorue impact. The major evidence quoted in support of this model is the enrichment of I; (a plamium-group element (PGE)) in the boundary clays. Closely spaced (era-scale) traverses through the K-T boundary at Stevns Klint (Denmark). Woodside Creek (New Zealand) and Richards Bay (South Africa) have been subjected to a trace clement
andstable
isotope investigation.
Intercomparison between these
data sets, ~ d co.elation with the broad data-base available in the literature, indicale that the chemistry of the boundary clays is not constant. Variations are more common than similarities; for example, the absolute values of Ir (and the olher POE) differ by more than an order of magnitude on a global scale and the choodrite normalized POE patterns of Sterns Klint are not hke those of Woodside Creek. The differences in POE patterns are difficult to explain by secondary alteration of a once-cbemicaIlyhomogeneous Ia) or, especially for elernents of such dubious crustal mobility, as Os and Ir. This fact, coupled to the recent observation that hot-spot volcanism (eg. Kilauea. Hawaii) can produce aerosols that are very enriched in siderophile eTements. (eg. It, Au. Ni. Co) lead the authors to suggest that the possible terrestrial component of the siderophi[e element ennchment in tile K-T clays has not been adequately identified. It is suggested that an extended period of Late Cretaceous volcanism can offer a satisfactory explanadon of tile K-T geochemical anomaly. This model would probably be more consistent with the observed ~tepwise, or gradual, palaeontological changes across this boundary., than tile "instant" cauastrophe predicted by the impact theory.
METEORITIC NOBLE CAS IN K-T BOUNDARY N. TAKAOKA and Y. MIURA (Dept. Earth Sci.~ Yamasata Univ. and Dept. Mineral. Geol. Sci., Yamaguchi Univ., Japan) We report result of noble gas analysis of clay sample from the K-T boundary at Steavns Klint in Denmark. The clay sample(SK-2-4) of 51.67 g was etched by 6N-HCI and conc. HF. After HF-etching for 2 days, the sample was washed by distilled water and dried. The weight decreased to 16.38 g by HF-etching. In the acid etching, we never heated nor used any oxidizing chemicals because heating releases loosely trapped gases and the oxidizing chemicals removes carbonaceous matters. Part(5.08 g) of residues was heated in a Ta furnace to melt. Techniques of noble gas analysis have been given elsewhere[l]. A large excess of He-3 (R=69Ra) and a slight depletion of Ne-20 were found relative to atmosph. ratios. High He ratios in deep-sea sediments and diamonds are accompanied by high Ne ratios[2,3]. A high He ratio in volcanic rocks is due to cosmogenic He[4,5]. The high He and low Ne ratios in this work are incompatible with the isotopic signature for deep-sea sediments and diamonds. The sampling site at Steavns Klint is on a sea shore and was underground in the past time. Therefore, cosmic-rays could not intrude the K-T boundary. These suggest the existence of a noble gas component different from that identified in terr. matters mentioned above: The cosmogenic or/and planetary-type gas. The present result suggests that the sediments from the K-T boundary at Stearns Klint contain matters of meteoritic origin. Ref. [i] Takaoka,N.(1976) Mass Spectr.24, 73-86. [2] Amari,S.,Ozima,M.(1986)Terra cognita 6, 102. [3] Honda,M. et ai.(1986) Terra cognita 6, 104. [4] Kurz,M.(1986) Geochim.Cosmochim.Acta 5--0,28552862. [5] Craig,H.,Podera,R.(1986) Proc. Natl. Acad. Sci. USA 83, 1970-1974
ISOTOPIC(St, Nd) AND CHEMICALVARIATIONSACROSSTHE K-T BOUNDARY. L.TURPIN, R. ROCCHIA,M. RENARD and D. BOCLET.
(CEA/IRDI, SEAINBat. 391, CEN Saclay, 91191 Gif sur Yvatte Codex, France). Samplescoilestedin threesites,8idart(S.W. France),StevnsKlint (Danemark) and Raton Basin (USA) have been analysedfor Sr and Nd isotoperatiosend trace elements.At Bidant,about 10m below the bounder,/,excursionsof the 87,Sr1865r ratiobetween 0.70805 and 0.70789 are observed,contrastingwith the smooth, regularincrease of 87Sr186Sr from -217m (Upper Campaoian). At Stavns KIint,
excursions are also observed, but at e lesser extent, and the 875r/86Sr ratio at the boundary is higher than at Bidart At Raton Basin, supposed to have been an inner sea during the K-T transition, the 875r/865r of the leacheles are rather constant at ~0.7095. 143Nd/144Nd ratios of the leaching residues are always slightly more radiogenic in the Ir-rlch layers, even in the continental lignite from Raton Basin, but no Important variations of the 67Sr/a6Sr ratios appear. Th-Hf-Ta and Ni-Or-Co abundance ratio determinations in these three sites, and also including additional eemples from Canavaca (Spain) emphasize (1) the constancy of terrigenous inputs from continental crust (2) transition element pattern evolution similar to those observed in metalliferous sediments and far from chondritic average. All these results lead to the following conclusions: ( I ) About 1 Ma before the K-T transition, the kinetic equilibrium which regulates the 87Sr/86Sr of sea water suffered dramatic perturbations: this correlates with ammonite extinctions (2) These perturbations do not onrretate between sites: this is probably due to the fact that the time scale ( 1 Me) is lower than the time residence of Sr in the oceans (3) Although 145Nd/ 144Nd present a minor, but systematic change at the boundary, the bulk geochemistry of terrigenous inputs does not present significant changes. No geochemical evidence unequivocally favouring either e terrestrial or an extra-terrestrial event can be deduced from our results, but the duration of the perturbation could well have beenat least I Me.