ISSN 1028�334X, Doklady Earth Sciences, 2011, Vol. 437, Part 2, pp. 449–454. © Pleiades Publishing, Ltd., 2011.Original Russian Text © O.A. Korchagin, V.A. Tsel’movich, 2011, published in Doklady Akademii Nauk, 2011, Vol. 437, No. 4, pp. 520–525.

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In modern views, one (or several) fragments of theBaptistina Asteroid originated from the inner part ofthe Asteroid Belt and cleaved about 160 Ma ago fallingto Earth at the end of the Cretaceous [1].

It is currently assumed that its fragments fell toEarth in the Late Maastrichtian, at the Cretaceous–Paleogene boundary, and in the Early Paleocene [2].The traces of fall of the biggest fragment found at theCretaceous–Paleogene boundary in the ChicxulubCrater (Mexico) are observed far beyond it as a blackclay horizon 1–3 cm thick with high Ir contents,altered “glassy” balls, impact quartz, and grains of Ni�spinel. The extinction of many groups of organismscoincides precisely with this impact event [3].

The Gubbio (Italy), Stevns Klint (Denmark), Car�avaca–Agosta (Spain), and Gams (Austria) sectionsare the etalon and most studied sections locatedbeyond the Chicxulub Crater with accurately deter�mined age and fall traces of fragments of this meteor�ite. The Stevns Klint [3–10] and Gams [11–13] sec�tions are especially well studied among the mentionedsections.

This study presents the first data on numeroussmall metallic particles of iron, copper, Fe–Ni, Fe–Ni–Co–Zn, and Fe–Cr alloys, magnetite and alumi�

nosilicate balls, and nanodiamond grains found in thetransitional layer of the black clay (Fish Clay). Thislayer was sampled by A.V. Dronov (Geological Insti�tute, Russian Academy of Sciences (RAS)) at theStevns Klint Section during the geological excursionon IGCP project no. 503 in 2009.

The natural clay chips and magnetic fraction fromthe rock were studied using the Tescan 2300 and Tes�can Vega II SEMs equipped with an Inca OxfordInstruments EDS and a Gatan cathodoluminescentdetector at the Borok Geophysical Observatory andthe Geological Institute, RAS. The chemical compo�sition of the particles and minerals was analyzed in allcases.

The transitional black clay layer 1–2 cm thickbetween Cretaceous and Paleogene at the Stevns KlintSection is mainly composed of smectites and containsextremely high Ir concentrations [3] and contents ofFe, Ni, Co, Zn, Mo, As, Se, Sb, etc. [4]. It is enrichedin OM, kerogen [5, 10], and numerous altered“glassy” impact balls [7]. It is considered that smec�tites were formed due to the surface weathering of vol�canosedimentary rocks, fragments of asteroids, andlocal material and further were redeposited in theDanish sedimentary basin [6]. Some smectites aresimilar to those from the underlying Maastrichtiansediments and developed after volcanic ashes [14].

The studied sample contains numerous large(about 0.8–1.3 mm across) brown altered “glassy”balls and their fragments. They have irregular spheru�litic, flat�spherulitic, or egglike morphology and areoften covered with calcite crust and plentiful cracks(Fig. 2, 1).

Cosmic Particles (Micrometeorites) and Nanospheres from the Cretaceous–Paleogene (K/T) Boundary Clay Layer

at the Stevns Klint Section, DenmarkO. A. Korchagina and V. A. Tsel’movichb

Presented by Academician Yu.G. Leonov August 10, 2010

Received November 17, 2010

Abstract—This paper presents new data on numerous small metallic particles of iron, copper, Fe–Ni, Fe–Ni–Co, and Fe–Cr alloys, magnetite, and aluminosilicate balls of cosmic origin found in the black clayboundary layer between the Cretaceous and Paleogene in the Stevns Klint Section (Denmark). The findingsimply that a fall of an asteroid to Earth 65 Ma ago was accompanied with falling of finely dispersed metallicparticles of extraterrestrial nature related to the asteroid fragments or to micrometeorites following the aster�oid or to the intense supply of cosmic dust. The huge amount of finely dispersed matter that fell to Earth atthat time should be considered in further reconstructions of events at the boundary of the Cretaceous andPaleogene.

DOI: 10.1134/S1028334X11040039

a Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia

b Borok Geophysical Observatory, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Borok, Yaroslavl oblast, 152742 Russia

GEOLOGY

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Many particles of native iron and copper, Fe–Cr,Fe–Zn, Fe–Co–Ni, and Fe–Ni–Co–Cu alloys withtraces of melting, and small magnetite and aluminosil�icate balls also occur in the same layer. The morphol�ogy and chemical composition of all particles areshown in Fig. 2 and Table 1.

The particles of native iron (Fe) (Fig. 2, 2, 3) occuras elongated, flat, and flat–curved bandlike fragmentsup to 10–70 µm with a distinct structure expressed inlongitudinal, slightly round or fused, partly overlap�

ping or loosely adjacent plates divided by furrows.Such particles are occasionally covered with a thinoxide film.

The particles of native copper (Cu) (Fig. 2, 4) formoval–elongated grains up to 5–10 µm with an unevenstructure.

It should be noted that the occurrence of nativenonoxidized iron and copper is probably related totheir entrapment by the reduced media and fast con�servation. It is also considered that some particles are

Fig. 1. The Stevns Klint Section. (a) Location of the section, (b) general view of the outcrop, (c) transitional layer of the blackclay (photograph by A.V. Dronov), from which sample SK�09 was taken (d) stratigraphic column of the boundary sedimentsbetween the Cretaceous and Paleogene. (1) Black clay layer, (2) alternation of black clay and gray marlstone, (3) gray marlstone,(4) chalk, chalklike limestone, (5) thin bedded limestone, (6) the surface of the break in sedimentation.

1 cm

1 2

3 4

5 6

K2m

P1

K2m

P1

Pal

eoge

ne

Copenhagen

Stevns Klint

(Denmark)BALTIC

SEA Cre

tace

ou

s(a)

(b)

(c)

(d)

Fig. 2. “Glassy” ball, metallic particles, nanospheres, and nanodiamonds from the transitional black clay layer of the Stevns KlintSection. SEM images. (1) Altered “glassy” ball, (2, 3) particle of native iron and magnetite with a longitudinal fused–scaly struc�ture, (4) isometric particle of native copper, (5, 6) spiral�like and platy particles of the Fe–Cr alloy, (7) flat–isometric particle ofthe Fe–Ni–Co–Cr alloy with transverse–scaly fused structure, (8) elongated–flat particle of the Fe–Zn alloy with longitudinal–scaly structure, (9) oblong particle of the Fe–Co–Ni alloy with randomly scaly structure, (10) isometric magnetite particle withfused (?) rims, (11) magnetite nanospheres, (12) aluminosilicate nanosphere, (13) magnetite nanosphere with takyr�shapedstructure composed of polyhedrons, (14) graphite particle (C) with grains of the Ni–Fe alloy and nanodiamonds (14b); (14a)grain of the Ni–Fe alloy and nanodiamond (Dm?) in the SE regime, (14b) Gatan cathodoluminescent detector image (the brightpoint is an intense shining nanodiamond grain). Places of chemical sampling of the particles are shown with white crosses andnumbers (see Table 1).

SK�09

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COSMIC PARTICLES (MICROMETEORITES) AND NANOSPHERES 451

200 µm

1

2

3

4

7

9

10

13

8

6

5

12 14

14b 14a

11

10 µm 5 µm

10 µm

10 µm

10 µm

10 µm

50 µm2 µm

10 µm 10 µm

2 µm 2 µm 10 µm

FeMt

Mt

Fe

Fe–Ni–Co–Cu

Fe–Co–Ni

Fe–Zn

Fe–Cr

Fe–Cr

Mt

Mt

Dm (?) Ni–Fe

Ni–Fe

Ni–Fe

Ni–FeNi–Fe

Dm (?)

Al–Si

Cu 1

1

23

59

6

2

1

3

6

5

1

1

3

2

45

4

3

Mt

1

3

5

4

5

1

3

2

3

C

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covered with a SiO2 nanolayer, which lets them not beoxidized. During the microprobe analysis, the beam ofelectrons pierces through this layer and, therefore,analyses are characterized by a small amount of SiO2.The study of iron particles with the cathodolumines�cent detector reveals the intense shining of the SiO2

nanolayer because iron should not shine.

The following particles of various metal alloys werefound in the black clay layer.

The particles of the Fe–Cr alloy (Fig. 2, 5, 6) occuras elongated, flat, and spiral�shaped plates 20–30 to60–70 µm long covered with round or fused, longitu�dinal or transverse edges forming a scaly structure.

The particles of the Fe–Zn alloy (Fig. 2, 8) formoblong plates up to 200 µm with an orbed or partlyfused longitudinal scaly structure.

The particles of the Fe–Ni–Co–Cu and Fe–Co–Nialloys (Fig. 2, 7, 9) were found as elongated plates upto 50–70 µm covered with rounded or partly fused,gently bordering fragments which form transverse–scaly or irregularly oriented scaly structure.

Nanospheres. Numerous small (0.5–5 µm across)magnetite and aluminosilicate balls were found in thestudied sample (Fig. 2, 11–13). Because of their size,it is suggested to call them nanospheres. Some magne�tite nanospheres are characterized by one�stage oxida�tion textures expressed in the takyr surface with sepa�rated and arcwise oriented polyhedrons. In addition to

Chemical compositions of metallic particles and magnetite nanospheres from the transitional black clay layer between theCretaceous and Paleogene from the Stevns Klint Section

SampleElement (wt %)

O Mg Al Si Ca Cr Mn Fe Zn Co Ni Cu Others

4/1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 0.00

5/1 3.21 0.00 0.00 0.54 0.00 11.41 0.00 84.84 0.00 0.00 0.00 0.00 0.00

5/2 5.06 0.00 0.00 0.50 0.44 11.12 0.00 82.89 0.00 0.00 0.00 0.00 0.00

5/3 5.20 0.00 0.00 1.22 1.25 10.55 0.00 81.77 0.00 0.00 0.00 0.00 0.00

6/3 19.96 0.00 1.43 3.79 1.96 9.47 0.00 63.49 0.00 0.00 0.00 0.00 0.00

6/4 3.10 0.00 0.00 0.00 0.00 11.57 0.90 84.43 0.00 0.00 0.00 0.00 0.00

6/5 65.97 0.00 0.00 3.26 4.61 2.67 0.00 20.03 0.00 0.00 0.00 0.00 S = 2.04; Cl = 1.43

6/6 5.05 0.00 0.37 0.61 0.77 11.63 0.65 80.92 0.00 0.00 0.00 0.00 0.00

7/1 3.61 0.00 5.81 0.91 0.50 0.00 0.00 47.36 0.00 22.66 15.34 3.58 P = 0.23

7/2 9.12 1.19 5.81 4.59 2.99 0.00 0.00 39.97 0.00 20.63 12.51 2.51 P = 0.68

7/3 3.50 0.00 7.67 0.45 0.00 0.00 0.00 45.48 0.00 24.21 15.07 3.63 0.00

7/5 4.37 0.00 7.71 0.38 0.17 0.00 0.00 46.27 0.00 24.07 13.40 3.63 0.00

7/6 4.71 0.00 6.97 0.54 0.00 0.00 0.00 45.88 0.00 24.32 14.41 3.17 0.00

7/9 3.26 0.27 4.50 1.24 0,25 0.00 0.00 47.39 0.00 24.13 15.94 3.02 0.00

8/1 5.96 0.59 0.00 0.33 0.00 0.00 0.00 75.20 17.91 0.00 0.00 0.00 0.00

8/2 7.55 0.00 0.00 0.26 0.00 0.00 0.00 63.57 28.61 0.00 0.00 0.00 0.00

8/5 38.61 1.01 1.21 3.27 11.08 0.00 0.00 39.20 5.62 0.00 0.00 0.00 0.00

9/1 12.24 0.00 9.87 9.57 8.22 0.00 0.00 33.40 0.00 18.65 8.05 0.00 0.00

9/3 14.68 0.00 8.47 2.08 0.00 0.00 0.00 43.34 0.00 20.86 10.57 0.00 0.00

9/4 3.02 0.00 6.39 0.82 0.00 0.00 0.00 47.78 0.00 28.39 13.60 0.00 0.00

9/5 11.35 0.00 8.20 0.00 0.00 0.00 0.00 47.29 0.00 20.06 13.09 0.00 0.00

11/1 36.66 0.00 4.76 7.31 3.06 0.00 0.00 48.22 0.00 0.00 0.00 0.00 0.00

11/2 34.61 0.00 3.82 10.80 4.53 0.00 0.00 46.24 0.00 0.00 0.00 0.00 0.00

11/3 48.43 0.00 5.87 10.01 5.02 0.00 0.00 30.67 0.00 0.00 0.00 0.00 0.00

11/5 42.07 0.00 4.12 6.30 3.92 0.00 0.00 43.57 0.00 0.00 0.00 0.00 0.00

12/3 56.10 0.00 13.05 18.22 1.61 0.00 0.00 7.02 0.00 0.00 0.00 0.00 K = 4.00

13/1 21.79 0.00 0.00 0.72 0.00 0.60 0.00 76.89 0.00 0.00 0.00 0.00 0.00

Note: Numbers of samples correspond to the objects illustrated in Fig. 2.

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magnetite nanospheres, aluminosilicate balls werealso observed (Fig. 2, 12).

Nanodiamonds. We should pay special attention tothe fact that we identified isometric graphite particles(Fig. 2, 14) with dissemination of small (0.5–1 µm) grainsof the Ni–Fe alloy and nanodiamonds (Fig. 2, 14b).Nanodiamonds 0.2–0.5 µm across were determinedby their intense shining in the Gatan cathodolumines�cent detector. Their cathodoluminescene spectrum issimilar to that of the detonation nanodiamonds usedas standards.

The revealed numerous particles of native iron,metal alloys, and magnetite microspheres, variable inmorphology, size, and chemical composition, arequite similar to the particles and microspheres earlierdescribed in the transitional layer of black claybetween Cretaceous and Paleogene in the Gams Sec�tion [12], where these particles associate with Ni�spinel grains [13], and they are also similar to metalparticles and microspheres from the Permian–Triassicboundary in the Meishan Section (China) [15].

Note first that despite the close similarity in assem�blages of metallic particles, micro� and nanospheresfrom the Gams [12] and Stevns Klint Sections, theyhave some distinct features. For example, the rocksfrom the Gams Section are devoid of “glassy” balls,while no Ni�spinel was found in the Stevns Klint Sec�tion. In addition, the metallic particles and nano�spheres from the Stevns Klint Section are considerablysmaller in comparison with the Gams Section. Theclay from the Stevns Klint Section contains very small(0.5–5 µm) magnetite and aluminosilicate nano�spheres, whereas the rock from the Gams Section ischaracterized by microspheres much larger in size(~15–20 and even up to 150 µm) [12]. The rocks fromboth the Stevns Klint and Gams sections contain nan�odiamonds [12], are free of nanospheres with Cradmixture and particles with Mo impurity, and arecharacterized by occasional occurrence of particles ofthe Ni–Fe alloy.

Thus, in spite of some differences in assemblages ofmetallic particles and micro� and nanospheres fromthe Stevns Klint and Gams sections, their occurrencein the same stratigraphic level at a significant distanceeach from other is evidence of the global (or subglobal)but not local reason for their formation and conserva�tion conditions.

The results of this study allow us to make the fol�lowing conclusions.

(1) The revealed assemblages of metallic particles,micro� and nanospheres and findings of Ni�spinel inthe Gams Section and altered “glassy” balls in theStevns Klint Section point to the fact that the fall ofthe asteroid fragment at the Cretaceous–Paleogeneboundary was accompanied by intense mechanicalfalling of extraterrestrial finely dispersed metallic par�ticles.

(2) The numerous studied metallic particles andnanospheres are composed of iron and copper andcontain admixtures of Ni, Zn, Co, Cr, and Mo. It isconsidered that high contents of these metals in theclay layer at the Cretaceous–Paleogene boundaryfrom the Stevns Klint and Gams sections, based ongeochemical analyses, are mostly related to the intensesupply in multiple mechanical finely dispersed metal�lic particles and magnetite micro� and nanospheres atthe moment of the layer accumulation and are causedless by the reduction conditions of sedimentation andtheir sorption by OM from seawater during diagenesis,or by secondary redistribution of H2S solutions andprecipitation of metals on the newly formed sulfides,or by strengthening of bacterial activity, as was sug�gested earlier [4–6, 8, 10]. This fact confirms the earlierconclusions that Ni, Co, and Zn and Ni–Fe oxidescould have an extraterrestrial nature [4, 7, 9, 10].

(3) The particles of native nonoxidized iron andcopper in the samples testify to the fact that, havingfallen to Earth, they occurred in the sedimentationbasin with reduction conditions and underwent fastconservation without oxidation or they reached mediaenriched in silicic acid.

In conclusion, the further research should considerthe intense fall to Earth of a huge amount of finely dis�persed metallic and aluminosilicate matter at the Cre�taceous–Paleogene boundary.

ACKNOWLEDGMENTS

The authors are grateful to colleagues from Geo�logical Institute, RAS, A.V. Dronov for the samplesand Yu.B. Gladenkov for constructive criticism duringthe writing of the manuscript. This work was sup�ported by the Russian Foundation for Basic Research,project no. 10�05�00117.

REFERENCES

1. W. F. Bottke, d. Vokrouhlicky, and D. Nesvorny, Nature449, 48–53 (2007).

2. G. Keller, Geol. Soc. Amer. Spec. Pap. 437, 147–178(2008).

3. L. W. Alvarez, W. Alvarez, F. Asaro, and H. V. Michel,Science 208, 1095 (1980).

4. B. Schmitz, Geochim. Comsmochim. Acta 49, 2361(1985).

5. B. Schmitz, P. Andersson, and J. Dahl, Geochim.Comsmochim. Acta 52, 229 (1988).

6. P. I. Premovic, N. Z. Pavlovich, M. S. Pavlovich, andN.D. Nikolic, Geochim. Comsmochim. Acta 57, 1433(1993).

7. B. Bauluz, D. R. Peacor, W. C. Elliot, Earth Planet. Sci.Lett. 182, 127–136 (2000).

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8. P. I. Premovic, N. D. Nikolic, I. R. Tonsa, et al., EarthPlanet. Sci. Lett. 177, 105 (2000).

9. R. Frei and K. M. Frei, Earth Planet. Sci. Lett. 203,691 (2002).

10. P. I. Premovic, M. Krsmanovic, B. Todorovic, et al.,J. Serb. Chem. Soc. 71, 793 (2006).

11. A. F. Grachev, I. L. Kamenskii, O. A. Korchagin, andH.A. Kollmann, Phiz. Zemli 34, (9), 61 (2007) [Izv.Phys. Solid Earth 43, 776 (2007)].

12. A. F. Grachev, O. A. Korchagin, V. A. Tsel’movich, andKh.A. Kollmann, Phiz. Zemli 44, (7), 42 (2008) [Izv.Phys. Solid Earth 44, 555 (2008)].

13. A. F. Grachev, V. A. Tsel’movich, O. A. Korchagin, andKh. A. Kollmann, Rus. J. Earth Sci. 10 (2), 1–11(2007).

14. V. A. Dritz, H. Lindgreen, B. A. Sakharov, et al., ClayMiner. 39, 367 (2004).

15. O. A. Korchagin, V. A. Tsel’movich, I. I. Pospelov, andBian Qiantao, Dokl. Akad. Nauk 432, 232–238 (2010)[Docl. Acad. Sci. 432, 631 (2010)].