Preliminary identification of fullerenes in lowermost Jurassic strata, Queen Charlotte Islands, British Columbia
Randall S. Perry*a, James W. Haggartb, Peter D. Warda
aDepartment of Earth and Space Sciences, Box 351310, University of Washington, Seattle, WA
98195-1310 USA
bGeological Survey of Canada, 101-605 Robson Street,
Vancouver, BC V6B 5J3 Canada
Abstract
The Triassic-Jurassic (TJ) mass extinction (~200 mya) event is one of the most severe in geologic history. It is also one of the most poorly understood. Few geologic sections containing the TJ boundary interval have been identified globally, and most of those are poorly preserved; the paucity of suitable stratigraphic sections has prevented corroborative geochemical studies of this interval. Recently, fullerene molecules (C60 to C200) have been shown to be present in the mass extinction boundary intervals of the Permian-Triassic (PT) event (~251.4 mya), as well as the well-known “dinosaur” extinction event of the Cretaceous-Tertiary (KT) (~65 mya). The presence of fullerenes in both these extinction intervals has been used to invoke an extraterrestrial impact cause for the extinctions. Preliminary results of laser desorption mass spectrometry (LDMS) of selected samples from the Kennecott Point TJ boundary section, Queen Charlotte Islands, British Columbia, suggest that fullerenes (C60 to ~C200) are present in the section, stratigraphically above the extinction interval (as defined by paleontological and isotopic data), but not actually within the interval itself. The presence of fullerenes may not be diagnostic of an impact event.
Keywords: Jurassic, Triassic/Jurassic Boundary, fullerenes, Queen Charlotte Islands, impact events
1. Introduction
1.1 General
Previous studies have shown that fullerenes, α-aminoisobutyric (AIB), and racemic isovaline (ISA) are present at the
well-known “dinosaur” extinction event of the Cretaceous-Tertiary (KT) (~65Ma),1, 2 and may be associated with the mass extinction event found at the Permian-Triassic (PT) boundary 3, 4 (~251.4 Ma) as well, although the latter is controversial. 5 The KT extinction occurred abruptly, and this, along with much other evidence (i.e., iridium anomalies, spherules, and shocked quartz), suggests that its cause might have been a bolide impact. 6-9 The extinction at the end of the Triassic Period is one of the five largest in the Phanerozoic with as many as 80% of the species lost. 10, 11 It is also one of the most poorly understood. Only a few sections have been identified worldwide and most of those are not well preserved and reflect a variety of different facies.12 The lack of suitable stratigraphic sections has made comparative geochemical studies difficult. 13-15 Evidence has been presented recently for a rapid negative excursion of carbon isotopes in marine Triassic-Jurassic (TJ) boundary rocks in British Columbia 16, Hungary 13, and Britain. 17 Presented here is chemical evidence for C60 and higher mass weight C70 to ~C200 that has been found in well-preserved marine strata of earliest Jurassic age in one of these sections, the Kennecott Point section at Queen Charlotte Islands, British Columbia, Canada (Fig. 1).
1.2 Fullerenes
The C60 molecule, buckminsterfullerene (Fig. 2), was discovered during laboratory experiments attempting to resolve the way in which carbon forms in space. 18 The higher mass weight molecules are called fullerenes. They have 12 pentagons and (n) hexagons, where the minimum for n equals 20. The smallest fullerene is the C60 and was named by Kroto et al. 18 after the philosopher/architect Buckminster Fuller. It has been suggested that fullerenes occur naturally in interstellar medium and may be widely distributed in the universe, particularly in the outflow of carbon stars. 19 They have been also reported in meteorites. 20, 21
1.3 Description of Locality
The Sandilands Formation is widely distributed across Queen Charlotte Islands, British Columbia. The formation spans the Triassic/Jurassic boundary and this interval has been intensively studied at two sites on the islands, Kunga Island (a previously proposed candidate for the global system boundary stratotype22) and Kennecott Point, the subject of this study. Paleontological studies show that these boundary sequences are expanded and contain microfossils and megafossils in sufficient numbers to allow a refined biostratigraphy. 23
The Kennecott Point section (Fig. 3,4) (latitude 53°54’48.4”N, longitude 133°09’17.8”W) is found in the intertidal zone and is cut by numerous small offsets. The Sandilands Formation here spans several hundred meters in thickness (Fig. 5). Strata dip at 15-25° and show minimal evidence of diagenetic alteration. 23 The Sandilands Formation consists of laminated parallel sandstone and siltstone, organic-rich black laminated shales (Fig. 6), locally with calcareous concretions, turbiditic siltstone and fine sandstone, tuffaceous sandstone, along with framboids, quartz and feldspar grains. The turnover of radiolarian taxa at the TJ boundary is the most important bioevent recorded in the Kennecott Point section; ammonoids (Choristoceras spp.) further refine the boundary interval. 23-25 A second important bioevent is found lower down in the section, at the Norian/Rhaetian boundary, and is marked by the disappearance of monotid bivalves.
Sedimentary structures found in the Kennecott Point section include common ripple-laminated beds and flame structures, and rare hummocky cross-stratification in coarser facies of the higher part of the section. Megafauna is rare throughout the TJ boundary interval.26
2. Methods
2.1 Sample Collection
Samples were collected in 1999 along a steel 300 m tape that spanned the section and was attached to a fixed point (0.0 m) in the Lower Hettangian (Jurassic) part of the Sandilands Formation. Stratigraphic positions of samples were recorded as meters below the 0.0 datum. The TJ boundary, as established by biostratigraphy, is found around the 112 m level above the base of the section, which corresponds with a level of –30 to –23 m along the tape. 16, 23 Samples collected were principally black shales. Additional samples were collected in 2001 from 0.0 m to –140 m and at ~6 cm increments from –13 m to –40 m and are the subject of an ongoing study.
2.2 Chemistry
Samples were prepared and analyzed in the laboratory of L. Becker, University of Washington and University of California, Santa Barbara. Ten grams of each rock sample were ground in a ball-mill or mortar and pestle. The homogenous powder was then demineralized using 100 ml of 1:1 48% reagent-grade hydrofluoric acid (HF) and distilled water and stirred for 12 hours in Nalgene containers. HF is unique in that it reacts with silica to form SiF4 and leaves the organic matter mostly unaltered. Insoluble fluorites can form, however, and the following procedure was employed. The samples were chilled in an ice bath and 62.5 g of crystalline boric acid was added. 27 The reaction of H3BO3 with HF is exothermic and the samples were chilled to ~0°C to prevent overheating. The amount of H3BO3 added was sufficient to convert all HF to BF3 by the reaction H3BO3 + 3HF = BF3 + 3H2O. The addition of boric acid eliminates the majority of fluoride salts and insoluble CaF2. The samples were stirred overnight, then washed in hot distilled H2O while being filtered under vacuum through 0.2 µm filters in a 142 mm stainless steel large-capacity vacuum filter device. The large amount of organic matter in the samples necessitated the use of the 120 cm2 filters. The samples were then washed several times in cold H2O through the same filter. The filters with samples were dried overnight in a 60°C oven. 28 A weighed portion of the dried carbonaceous residue was re-fluxed with toluene for 24 hours using a soxhlet extraction tube with a cellulose filter thimble. The soxhlet tube was attached to Allihn condensor and a flask. The toluene solution was then concentrated using a roto-evaporator. A preliminary analysis of the concentrate was made for fullerenes before refluxing a second time, using 1,2,4-trichlorobenzene (TCB) for another 24 h.
2.3 LDMS
Laser desorption (linear) time-of-flight mass spectrometry (LDMS) was used for detection of fullerenes in the TCB and toluene extracts. Approximately one microliter of the concentrated solution was placed on a mount and introduced into the Kratos LDMS under high vacuum. The spectra produced were averaged using 200 or more laser hits. A C60 standard was run and easily detected in the LDMS.
2.4 Amino Acids
Samples were crushed to a powder. All glassware was cleaned and heated at 500°C for 3 h. Amino acid extracts were prepared by adding double-distilled water to each sample and heating for 24 h at 100°C in a sealed glass tube. The supernatant was decanted and dried and the residue hydrolyzed in 6N double-distilled HCl for 3 h at 100°C. The hydrolyzed residue was then dried and passed through a desalting column containing AG 50W-X8 resin (Bio Rad). The amino acid fraction was then eluted with aqueous NH4OH. The eluate was dried, re-suspended in aqueous borate buffer at pH 9.4, and dried again to remove ammonia. The amino acid residue was then re-dissolved in double-distilled water and derivatized by OPA/NAC (o-phthaldialdehyde/N-acetyl L-cysteine). The derivatives were separated by reverse phase HPLC with fluorescence detection and identified by comparison of retention times with standards. 2, 29 A control blank was processed and analyzed in parallel with the samples.
2.5 Scanning Electron Microscopy (SEM) and Energy Dispersive Microanalysis System (EDAX)
SEM analyses were undertaken at the Pacific Northwest National Laboratories (PNNL), Environmental Microbiology Sciences Laboratories (EMSL) at Richland, Washington. SEM imaging was performed using a LEO 982 Field Emission Scanning Electron Microscope, an ultra-high performance scanning electron microscope. The SEM has two secondary electron detectors: below lens and in-lens for high resolution imaging. The backscattered electron detector is solid state and is optimized for short working distances.
An Oxford ISIS was used for EDAX chemical analyses. A SiLi detector, having 128 eV resolution, is capable of light element analyses, elemental mapping digital imaging, and microscope automation, and can combine compositional information with a secondary electron image in a software package called CAMEO. Samples were coated with platinum.
3. Results
3.1 Mineralogy
Examination of thin sections and SEM/EDAX showed that the rocks are laminated black shales showing clay mineral and kerogen laminae with ~6µm framboids scattered throughout. The black shales are interstratified with sub-millimeter- to millimeter-scale fine-grained turbidites. Angular quartz grains were noted in many thin sections.
Of particular interest for this study are thin sections from strata where fullerenes were found. Below is a list of thin section observations starting just above the earliest fullerenes samples at the –18.0m point and continuing past the –19.6m to a clay/Fe layer at –21.5m:
-16.9 Laminated shale with a 2 mm turbidite layer
-17.2 Fine grained sandstone
-17.4 Fine grained well-laminated parallel sandstone
-17.6 Laminated fine grained sandstone
-17.8 Laminated shale with calcareous concretions
-18.0 Well-laminated shale
-18.0 B (a second sample) shows bioturbation
-18.3 Well-laminated black shale
-18.4 Well-laminated turbidite, fine grained sandstone
-18.6 Laminated shale and well laminated turbidite
-18.8 ibid. as –18.6
-19.2 Fine grained sandstone and black shale
-19.3 Fine grained black shale
-19.6 Abundant diagenetic secondary calcite with angular quartz and abundant volcanic rock
-19.8 Laminated black shale
-20.0 Fine grained sandstone
-20.2 Laminated black shale similar to –19.8
-20.4 Laminated black shale
-20.6 ibid. as –20.4
-21.2 Shale with secondary calcite in concretions
-21.5 Clay layer with substantial Fe
-21.6 Laminated black shale
3.2 Fullerenes
A total of 13 samples from –0.0 to –40 m levels of the section were tested for fullerenes.
We initially concentrated our search for fullerenes in the –30 m region since this was where the boundary was suggested by both paleontological
and stable isotope data.7 A number of samples were tested in the –18m to –30m range. Within this interval, fullerenes. were detected in only two of the samples tested, the –18.0m (Fig. 7) and –19.6m (Fig. 8) samples.
The fullerenes spectrum from the –19.6m sample (Fig. 8) has a possible peak at C60 and C84 while no C60 was detected in the –18.0 m sample. Figure 7 is a spectrum showing that the sample contained lower molecular weight carbon and polycyclic aromatic hydrocarbons (PAHs). The distribution of higher mass weight fullerenes in Figures 7 and 8 differs from fullerenes found in the Stevns Klint KT and PT (Fig. 9,10) boundary sections. 3, 4, 28
3.3 Amino Acid
Small quantities of AIB and ISA (Fig. 11) were detected in only one sample (-18.0 m). The testing included samples from the PT boundary. The peaks detected represent values just at the limit of detection and could not be duplicated in subsequent tests, suggesting they may be artifacts.
4. Discussion
The thin laminae coupled with framboid size 30 are indicative of a deeper-water anoxic environment for the Sandilands Formation in the Kennecott Point section, which may account for the distinct lack of
megafauna in the shales. Fullerenes are present in only two samples analyzed, and both of these are found well above the TJ boundary interval, as defined by both paleontological and isotopic data. The presence of turbidites in the section, and the stability of the fullerene molecule itself, brings into question the source of the fullerenes. Whether the caged fullerenes molecules contain signatures of their origins, in the form of noble gases, 1, 28, 31 still does not address the question of their source. One possibility is that the Kennecott Point fullerenes are related to a possible impact event, proposed by Olsen et al.31 to explain the end- Triassic extinction, and have been reworked into somewhat younger strata. Alternatively, they may be significantly older then the Sandilands Formation strata and have been reworked into the formation after weathering from another section. The stratigraphic separation of the fullerenes
from the TJ boundary interval in the Kennecott Point section may also be explained by considering multiple impacts, or the possibility that fullerenes can occur in strata from sources other than impact.
5. Conclusions
Fullerenes have been found in two samples from the Queen Charlotte Islands several meters above the TJ boundary interval, as defined by a significant die-out of Rhaetian fossil taxa and stable isotope data. They were not found at any other stratigraphic levels tested and their source is unknown. They may be reworked from an older stratigraphic interval. If they are assumed to be indicative of an impact event, they do not correlate with the negative 13C excursion of Ward et al. (2001), 16 which took place earlier.
Our data show that fullerenes are present outside of the TJ extinction interval in the stratigraphic section on Queen Charlotte Islands. Consequently, invoking the presence of fullerenes to identify extraterrestrial impacts at other
levels in the geologic record may be an invalid assumption. The fullerene data, taken together with the lack of definitive evidence of AIB and ISA, iridium, and shocked quartz in sections studied to date, as well as the lack of evidence of an impact crater and conflicting carbon data in other worldwide sections, suggests that the hypothesis of an extraterrestrial impact as a causative mechanism of the Triassic-Jurassic extinction enjoys only limited support.
Acknowledgments
This work was supported in large part by an NSF Integrative Graduate Education and Research Traineeship (IGERT) grant (#DGE-9870713) to the senior author. NASA Astrobiology Institute and the Washington Space Grant Consortium also provided support. We especially thank Luann Becker and Richard Stewart for much discussion and laboratory help, Jeff Bada and Oliver Bota for assistance, hospitality, and use of their laboratory facilities at Scripps Institute of Oceanography.
References
1. L. Becker, R. J. Poreda, and T. E. Bunch, "The origin of fullerenes in the 65 myr Cretaceous/Tertiary boundary," Lunar and Planetary Science XXXI (1999).
2. M. Zhao and J. L. Bada, "Extraterrestrial amino acids in Cretaceous/Tertiary boundary sediments at Stevns Klint, Denmark," Nature 339, 463-465 (1989).
3. L. Becker and R. J. Poreda, "An extraterrestrial impact at the Permian-Triassic boundary," Science 293, U-4-U6 (2001).
4. L. Becker, R. J. Poreda, A. G. Hunt, T. E. Bunch, and M. Rampino, "Impact event at the Permian-Triassic Boundary: Evidence from extraterrestrial noble gases in fullerenes," Science 291, 1530-1533 (2001).
5. D. H. Erwin, "Impact at the Permo-Triassic Boundary: A critical evaluation," Astrobiology 3(1), 67-74 (2003).
6. L. W. Alvarez, W. Alvarez, and H. V. Michel, "Extraterrestrial cause for the Cretaceous/Tertiary extinction," Science 208, 1095-1108 (1980).
7. B. F. Bohor, E. E. Foord, P. J. Modreski, and D. M. Triplehorn, "Mineralogic evidence for an Impact event at the Cretaceous-Tertiary boundary," Science 224, 867-868 (1984).
8. B. F. Bohor, P. J. Modreski, and E. E. Foord, "Shocked quartz in the Cretaceous-Tertiary boundary clays: evidence for a global distribution," Science 236, 703-709 (1987).
9. F. T. Kyte, "A mereorite from the Cretaceous-Tertiary boundary," Nature 396, 237-239 (1998).
10. A. Hallam and P. Wignall, Mass Extinctions and their Aftermath (Oxford University Press, Oxford, 1997).
11. J. J. Sepkoski, "Ten years in the library: new data confirm paleontological patterns," Paleobiology 19, 43-51 (1993).
12. A. Hallam and P. Wignall, in Mass Extinctions and Their Aftermath (Oxford University Press, Oxford, 1997), p. 320.
13. J. Pálfy, A. Demeny, J. Haas, M. Hetenyi, M. J. Orchard, and I. Veto, "Carbon isotope anomaly and other geochemical changes at the Triassic-Jurassic boundary from a marine section in Hungary," Geology 29(11), 1047-1050 (2001).
14. R. Morante and A. Hallam, "Organic carbon isotopic record across the Triassic-Jurassic boundary in Austria and its bearing on the cause of the mass extinction," Geology 24(5), 391-394 (1996).
15. A. Hallam and P. B. Wignall, "Facies changes across the Triassic-Jurassic boundary in Nevada, USA," Journal of the Geological Society (London) 157(1), 49-54 (2000).
16. P. D. Ward, J. W. Haggart, E. S. Carter, D. Wilbur, H. W. Tipper, and T. Evans, "Sudden productivity collapse associated with the Triassic-Jurassic Boundary mass extinction," Science 292, 1148-1151 (2001).
17. S. P. Hesselbo, S. A. Robinson, F. Surlyk, and S. Piasecki, "Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle pertubation: a link to initiation of massive volcanism?", Geology,30(3), 251-254 (2002).
18. H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl, and R. Smalley, "C60: Buckministerfullerene," Nature 318, 162-163 (1985).
19. J. P. Hare and H. W. Kroto, "A postbuckminsterfullerene view of carbon in the galaxy," Acc. Chem. Res. 25, 106-112 (1992).
20. L. Becker, J. L. Bada, R. E. Winans, and T. E. Bunch, "Fullerenes in Allende meterorite," Nature 372, 507 (1994).
21. P. J. F. Harris, R. D. Vis, and D. Heymann, "Fullerene-like carbon nanostructures in the Allende meteorite," Earth and Planetary Science Letters 183, 355-359 (2000).
22. E. S. Carter and H. W. Tipper, "Proposal of Kunga Island, Queen Charlotte Islands, British Columbia, Canada as Triassic/Jurassic global boundary stratotype," International Subcommission on Jurassic Stratigraphy Newsletter 27(1999).
23. J. W. Haggart, E. S. Carter, M. J. Beattie, P. S. Bown, R. J. Enkin, D. A. Kring, M. J. Johns, V. J. McNicoll, M. J. Orchard, R. S. Perry, C. S. Schröder-Adams, P. L. Smith, L. B. Suneby, H. W. Tipper, and P. D. Ward, "Stratigraphy of Triassic/Jurassic Boundary strata Queen Charlotte Island, British Coumbia: Potential global system stratotype boundary," IGCP #458 (Triassic-Jurassic Events), Southwest England Field Workshop, Somerset, 10-13 (2001).
24. P. D. Ward, D. R. Montgomery, and R. Smith, "Altered river morphology in South Africa related to the Permian-Triassic extinction," Science 289, 1740-1743 (2000).
25. H. W. Tipper, E. S. Carter, M. J. Orchard, and E. T. Tozer, "The Triassic-Jurassic (T-J) boundary in Queen Charlotte Islands, British Columbia defined by ammonites, conodonts and radiolarians," in Geobios Memoire Special: Lyon Universite Claude Bernard, E. Cariou and P. Hantzpergue, eds. (1994), pp. 485-492.
26. E. S. Carter, "Biochronology and paleontology of uppermost Triassic (Rhaetian) radiolarians, Queen Charlotte Islands, British Columbia, Canada," in Memories de Geolgie (Lausanne), (1993), p. 175.
27. T. L. Robl and B. H. Davis, "The use of aqueous trifluoride in deashing organic-rich rocks and sediments," Organic Geochemistry 20, 249-272 (1993).
28. L. Becker, R. J. Poreda, and T. E. Bunch, "Fullerenes: An extraterestrial carbon carrier phase for noble gases," PNAS 97(7), 2979-2983 (2000).
29. M. Zhao and J. L. Bada, "Determination of alpha-diakylamino acids and their enantiomers in geological samples by high-performance liquid chromatography after derivatization with a chiral adduct of 0-phthaldialdehyde," Journal of Chromatography 690, 55-63 (1995).
30. R. T. Wilkin, M. A. Arthur, and W. E. Dean, "History of water column anoxia in the Black Sea indicated by pyrite framboid size distribution," Earth and Planetary Science Letters 148, 517-525 (1997).
31. L. Becker, R. J. Poreda, and J. L. Bada, "Extraterrestrial helium trapped in fullerenes in the Sudbury impact structure," Science 272, 249-252 (1996).
