Spherule beds 3.47-3.24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution.

Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approximately 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.

[1]  A. Glikson.  Early precambrian asteroid impact-triggered tsunami: excavated seabed, debris flows, exotic boulders, and turbulence features associated with 3.47-2.47 Ga-old asteroid impact fallout units, Pilbara Craton, Western Australia. , 2004, Astrobiology.

[2]  B. Glass,et al.  SPHERULE LAYERS—RECORDS OF ANCIENT IMPACTS , 2004 .

[3]  D. Lowe,et al.  High Archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3.5 Ga Swaziland Supergroup, South Africa , 2003 .

[4]  G. Lugmair,et al.  Early Archean spherule beds; chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type , 2003 .

[5]  D. Lowe,et al.  An Archean Impact Layer from the Pilbara and Kaapvaal Cratons , 2002, Science.

[6]  B. Kamber,et al.  Tungsten isotope evidence from ∼3.8-Gyr metamorphosed sediments for early meteorite bombardment of the Earth , 2002, Nature.

[7]  K. Pope.  Impact dust not the cause of the Cretaceous-Tertiary mass extinction , 2002 .

[8]  A. Glikson.  The astronomical connection of terrestrial evolution: crustal effects of post-3.8 Ga mega-impact clusters and evidence for major 3.2±0.1 Ga bombardment of the Earth–Moon system , 2001 .

[9]  B. Simonson,et al.  The Sedimentary Record of Extraterrestrial Impacts in Deep‐Shelf Environments: Evidence from the Early Precambrian , 2001, The Journal of Geology.

[10]  H. Robey,et al.  Bedforms produced by impact-generated tsunami, ∼2.6 Ga Hamersley basin, Western Australia , 2000 .

[11]  P. Renne,et al.  Lunar impact history from (40)Ar/(39)Ar dating of glass spherules , 2000, Science.

[12]  A. Glikson.  Oceanic mega-impacts and crustal evolution , 1999 .

[13]  J. Smit.  THE GLOBAL STRATIGRAPHY OF THE CRETACEOUS-TERTIARY BOUNDARY IMPACT EJECTA , 1999 .

[14]  D. Lowe,et al.  Foreland basin sedimentation in the Mapepe Formation, southern-facies Fig Tree Group , 1999 .

[15]  D. Lowe,et al.  STRUCTURAL DIVISIONS AND DEVELOPMENT OF THE WEST-CENTRAL PART OF THE BARBERTON GREENSTONE BELT , 1999 .

[16]  D. Lowe,et al.  Stratigraphy of the west-central part of the Barberton Greenstone Belt, South Africa , 1999 .

[17]  G. Byerly.  KOMATIITES OF THE MENDON FORMATION : LATE-STAGE ULTRAMAFIC VOLCANISM IN THE BARBERTON GREENSTONE BELT , 1999 .

[18]  C. Koeberl,et al.  Ocean Drilling Project Hole 689B spherules and upper Eocene microtektite and clinopyroxene‐bearing spherule strewn fields , 1999 .

[19]  D. Lowe.  Petrology and sedimentology of cherts and related silicified sedimentary rocks in the Swaziland Supergroup , 1999 .

[20]  N. Sleep,et al.  Refugia from asteroid impacts on early Mars and the early Earth , 1998 .

[21]  Knauth Lp.  Salinity history of the Earth's early ocean , 1998 .

[22]  G. Lugmair,et al.  Early solar system timescales according to 53Mn-53Cr systematics , 1998 .

[23]  G. Byerly,et al.  IIb trioctahedral chlorite from the Barberton greenstone belt: crystal structure and rock composition constraints with implications to geothermometry , 1997 .

[24]  M. Walsh,et al.  Prolonged magmatism and time constraints for sediment deposition in the early Archean Barberton greenstone belt: evidence from the Upper Onverwacht and Fig Tree groups , 1996 .

[25]  C. Koeberl,et al.  Early Archaean spherule beds in the Barberton Mountain Land, South Africa: no evidence for impact origin , 1995 .

[26]  B. Bohor,et al.  Origin and diagenesis of K/T impact spherules—From Haiti to Wyoming and beyond , 1995 .

[27]  D. Lowe,et al.  Spinel from Archean impact spherules , 1994 .

[28]  C. Koeberl,et al.  Geochemistry and mineralogy of Early Archean spherule beds, Barberton Mountain Land, South Africa: evidence for origin by impact doubtful , 1993 .

[29]  R. Hart,et al.  Earth's earliest continental lithosphere, hydrothermal flux and crustal recycling , 1993 .

[30]  D. Lowe,et al.  Noble metal abundances in an Early Archean impact deposit. , 1992, Geochimica et cosmochimica acta.

[31]  H. Melosh,et al.  Melt droplet formation in energetic impacts , 1991 .

[32]  G. Byerly,et al.  Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evaporation. , 1991, Earth and planetary science letters.

[33]  J. Hanor,et al.  Isovolumetric Silicification of Early Archean Komatiites: Geochemical Mass Balances and Constraints on Origin , 1990, The Journal of Geology.

[34]  W. Boynton,et al.  Proximal Cretaceous-Tertiary Boundary Impact Deposits in the Caribbean , 1990, Science.

[35]  Harold J. Morowitz,et al.  Annihilation of ecosystems by large asteroid impacts on the early Earth , 1989, Nature.

[36]  N. Beukes,et al.  Geochemistry and sedimentology of a facies transition from limestone to iron-formation deposition in the early Proterozoic Transvaal Supergroup, South Africa , 1989 .

[37]  D. Lowe,et al.  Geological and Geochemical Record of 3400-Million-Year-Old Terrestrial Meteorite Impacts , 1989, Science.

[38]  R. J. Hart,et al.  Platinum group elements in a 3.5 Ga nickel‐iron occurrence: Possible evidence of a deep mantle origin , 1989 .

[39]  T. Hansen,et al.  A Tsunami Deposit at the Cretaceous-Tertiary Boundary in Texas , 1988, Science.

[40]  David J. Stevenson,et al.  Impact frustration of the origin of life , 1988, Nature.

[41]  J. Hanor,et al.  Origin and timing of the metasomatic silicification of an early archean komatiite sequence, barberton mountain land, South Africa , 1987 .

[42]  R. Buick.  Comments and Replies on “Early Archean silicate spherules of probable impact origin, South Africa and Western Australia”: COMMENT , 1987 .

[43]  D. Lowe,et al.  Comments and Replies on “Early Archean silicate spherules of probable impact origin, South Africa and Western Australia” , 1987 .

[44]  B. French.  Comments and Replies on “Early Archean silicate spherules of probable impact origin, South Africa and Western Australia” , 1987 .

[45]  B. Glass,et al.  Late Eocene North American microtektites and clinopyroxene‐bearing spherules , 1985 .

[46]  I. Stanistreet,et al.  Cherts of the Barberton Greenstone Belt Interpreted as Products of Submarine Exhalative Activity , 1985, The Journal of Geology.

[47]  D. Stevenson.  Implications of Very Large Impacts for Earth Accretion and Lunar Formation , 1985 .

[48]  T. Heinrichs.  The Umsoli chert, turbidite testament for a major phreatoplinian event at the onverwacht/fig tree transition (Swaziland supergroup, Archaean, South Africa) , 1984 .

[49]  A. Montanari,et al.  Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition , 1983 .

[50]  T. Reimer.  Pseudo-Oolites in Rocks of the Ulundi Formation, Lower Part of the Archaean Fig Tree Group (South Africa) , 1983 .

[51]  Anthony J. Martin,et al.  Archean abiogenic and probable biogenic structures associated with mineralized hydrothermal vent systems and regional metasomatism, with implications for greenstone belt studies , 1982 .

[52]  T. Ahrens,et al.  The interaction of the Cretaceous/Tertiary Extinction Bolide with the atmosphere, ocean, and solid Earth , 1981 .

[53]  I. Stanistreet,et al.  Do graded units of accretionary spheroids in the Barberton Greenstone Belt indicate Archaean deep water environment? , 1981, Nature.

[54]  D. Lowe,et al.  The Oldest Marine Carbonate Ooids Reinterpreted as Volcanic Accretionary Lapilli, Onverwacht Group, South Africa , 1978 .

[55]  T. Reimer,et al.  A sedimentary barite deposit from the Archean Fig Tree Group of the Barberton Mountain Land (South Africa) , 1977 .

[56]  D. Lowe,et al.  Sedimentology of the Onverwacht Group (3.4 Billion Years), Transvaal, South Africa, and Its Bearing on the Characteristics and Evolution of the Early Earth , 1977, The Journal of Geology.

[57]  C. D. Conley.  Origin of Distorted Ooliths and Pisoliths , 1977 .

[58]  D. A. Papanastassiou,et al.  Isotopic evidence for a terminal lunar cataclysm , 1974 .

[59]  T. Reimer,et al.  Petrology and Geochemistry of Early Precambrian Graywackes from the Fig Tree Group, South Africa , 1970 .

[60]  H. Melosh,et al.  Impacts do not initiate volcanic eruptions: Eruptions close to the crater: Comment and Reply: REPLY , 2004 .

[61]  A. Glikson.  Impacts do not initiate volcanic eruptions: Eruptions close to the crater: Comment and Reply COMMENT , 2004 .

[62]  Graham Ryder,et al.  Bombardment of the Hadean Earth: wholesome or deleterious? , 2003, Astrobiology.

[63]  D. Lowe,et al.  Early Archean Spherule Beds: Chromium Isotopes Confirm Origin through Multiple Impacts of Projectiles of Carbonaceous Chondrite Type: Comment and Reply , 2003 .

[64]  A. Glikson.  Early Archean spherule beds: Chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type: Comment and Reply COMMENT , 2003 .

[65]  B. Simonson.  Petrographic criteria for recognizing certain types of impact spherules in well-preserved precambrian successions. , 2003, Astrobiology.

[66]  C. Koeberl,et al.  Early Archean Spherule Beds in the Barberton Mountain Land, South Africa: Impact or Terrestrial Origin? , 2000 .

[67]  D. Lowe,et al.  The oldest impact deposits on Earth - First confirmation of an extraterrestrial component , 2000 .

[68]  S. Mojzsis,et al.  Heavy Bombardment on the Earth at ~3.85 Ga: The Search for Petrographic and Geochemical Evidence , 2000 .

[69]  L. P. Knauth,et al.  Salinity history of the Earth's early ocean , 1998, Nature.

[70]  Carl Sagan,et al.  Comets as a source of prebiotic organic molecules for the early Earth. , 1997 .

[71]  A. Montanari,et al.  Coarse-grained, clastic sandstone complex at the K/T boundary around the Gulf of Mexico: Deposition by tsunami waves induced by the Chicxulub impact? , 1996 .

[72]  Chengjie Liu,et al.  The Cretaceous-Tertiary catastrophic event at Millers Ferry, Alabama , 1996 .

[73]  Chengjie Liu,et al.  High-resolution biostratigraphy of sea-level low, biotic extinction, and chaotic sedimentation at the Cretaceous-Tertiary boundary in Alabama, north of the Chicxulub Crater , 1996 .

[74]  M. Cloete.  Aspects of volcanism and metamorphism of the Onverwacht group lavas in the South-Western portion of the Barberton greenstone belt. , 1994 .

[75]  J. Kasting.  Impacts and the origin of life. , 1990, Earth and mineral sciences.

[76]  B. Glass,et al.  Microkrystites - A new term for impact-produced glassy spherules containing primary crystallites , 1988 .

[77]  David J. Stevenson,et al.  Origin of the Moon-The Collision Hypothesis , 1987 .

[78]  D. Lowe,et al.  Early Archean silicate spherules of probable impact origin, South Africa and Western Australia , 1986 .