Flaxbourne River Research Articles

TEM study of meteorite impact glass at New Zealand Cretaceous–Tertiary sites: evidence for multiple impacts or differentiation during global circulation?

Study by transmission electron microscopy of samples from the Cretaceous–Tertiary (K–T) boundary clay at Flaxbourne River and Woodside Creek, New Zealand, has revealed the occurrence of nanometer-sized meteorite impact-derived glass. The average glass composition is exceptionally Ca-rich and is distinct from other glass found on Earth, apart from glass inferred to be of impact origin at Mexican and Haitian K–T sites. The glass shards are partially altered to montmorillonite-like smectite, with the dominant interlayer cation, Ca, reflecting the composition of the parent glass. The data imply a heterogeneous global distribution in composition of K–T boundary impact glass: Si-rich and Ca-rich in Mexico and Haiti, Si-rich in Denmark, and Ca-rich in New Zealand. This heterogeneous distribution may relate to dispersal processes similar to those used to account for the asymmetric distribution of clastic debris from the Chicxulub impact site. However, recent discovery of an impact crater of K–T boundary age in Ukraine raises the possibility of impact clusters which produce material of heterogeneous composition.

Paleoenvironmental changes across the Cretaceous/Tertiary boundary at Flaxbourne River and Woodside Creek, eastern Marlborough, New Zealand

An integrated study of variation in siliceous microfossils, lithofacies, and other geochemical guides to environmental conditions through the Cretaceous/Tertiary (K/T) boundary transition at Flaxbourne River and Woodside Creek, coastal eastern Marlborough, indicates that the K/T impact disrupted oceanic conditions along the continental margin of eastern New Zealand for c. 1 m.y. Initial effects of the K/T event were a major reduction in carbonate production, associated with calcareous plankton extinctions, and significant increases in terrigenous clay and biogenic silica content. An absence of radiolarian extinctions or significant negative excursions in paleo‐productivity indicators (Ba, d13C) at the boundary, followed by rapid increases in the abundance of diatoms and spumellarian radiolarians, indicate that biogenic silica production partly compensated for the collapse in calcareous plankton. The earliest Paleocene recovery of calcareous plankton was short‐lived, giving way to a progressive increase in siliceous plankton abundance over c. 500 000 yr, which culminated in a c. 400 000 yr episode of peak biogenic silica production. The dominance of siliceous facies, coupled with the abundance of diatoms and spumellarian radiolarians, indicates climatic or oceanic conditions were significantly cooler than in the Late Cretaceous. Stepped increases in biogenic silica production show c. 100 000 yr periodicity, suggesting that early Paleocene lithofacies changes were influenced by climate forcing agents at the eccentricity bandwidth.

Wavelet analysis of variations in geochemical and microfossil data across the Cretaceous/Tertiary boundary at Flaxbourne River, New Zealand

Wavelet analysis of 58 elemental, mineralogical, and bioclastic variables, taken from 33 samples collected at ‐2 to +5 m across the Cretaceous/Tertiary (K/T) boundary at Flaxbourne River, eastern Marlborough, identified 9 classes of variables exhibiting 3 main styles of behaviour: (1) classes 1, 3, and 5 exhibit abrupt enrichment at the boundary with either sudden, rapid, or gradual decline in the Paleocene (e.g., Zn, Cr, Pb, Ni, Al, Fe, Rb, Th, Ga, quartz); (2) classes 2 and 4 exhibit an abrupt decrease at the K/T boundary followed by progressive decline in the Paleocene (e.g., Ca, Mn, Sr, La, Sc, calcite), and (3) classes 6, 7, and 9 exhibit a minor change at the boundary followed by progressive increase in the Paleocene (e.g., Ba, Si, Ba/Ti, radiolarian diversity, radiolarian abundance, diatom/ radiolarian ratio). In class 8 (δ13C, δ18O) there is little change other than a gradual increase or gradual decrease across the boundary. Classes 1–6 include 37 of the 59 variables analysed and the first principal component accounts for ≥75% of variation, indicating a significant level of congruity through time that is lacking among the trajectories of the wavelet trends of the members of classes 7–9. Nine parameters display unclassifiable trends, due either to truly unique trends or anomalous values. The analysis was undertaken with no prior geological‐based grouping of any of the variables. Nonetheless, the resulting classification groups well‐established K/T boundary markers as well as paleoenvironmental indicators. However, where postdepositional processes have affected the values of parameters (e.g., opal‐CT, stable isotopes), wavelet trends either display a low level of coherency and/or fail to follow simple geological trends.

New Zealand perspective on global change from late Cretaceous to early Eocene: (b) the Cretaceous—Tertiary transition at Flaxbourne River, eastern Marlborough

(2000). New Zealand perspective on global change from late Cretaceous to early Eocene: (b) the Cretaceous—Tertiary transition at Flaxbourne River, eastern Marlborough. GFF: Vol. 122, No. 1, pp. 73-74.

Cretaceous‐Tertiary foraminiferal succession at Flaxbourne River, Marlborough, New Zealand

The stratigraphically and biostratigraphically most complete Cretaceous‐Tertiary (K‐T) boundary succession yet identified in New Zealand occurs in bathyal limestones of the Mead Hill Formation at Flaxbourne River, coastal Marlborough. It is one of three New Zealand K‐T sections with a well‐delineated “fireball” layer, containing anomalous iridium, soot particles, and fullerenes, and it contains a highly fossiliferous latest Cretaceous marl unit, not seen in other sections, immediately underlying the K‐T boundary clay. The c. 50 m thick Flaxbourne section is the only New Zealand locality known with an essentially complete sequence of earliest Paleocene foraminiferal zones. These include (K‐T boundary is zero datum): Guembelitria cretacea Zone (P0), 0.0–0.07 m; Parvularugoglobigerina eugubina Zone (P?), 0.07–0.24 m; P. eugubina‐Subbotina triloculinoides Subzone (P1a), 0.24–0.40 m; S. trilo‐culinoides‐Globanomalina compressa/Praemurica inconstans Subzone (P1b), 0.40–0.50 m; and Globanomalina compressa/Praemurica inconstans‐Praemurica uncinata Subzone (P1c), 0.50–11.5 m. Strata from 11.5 m to the highest exposed beds at c. 38 m are classified as undifferentiated Paleocene. Cretaceous planktic “survivor taxa” occur up to 0.40 m but are replaced rapidly above Zone P0 by Paleocene taxa. Latest Cretaceous strata are dominated by Heterohelix/ Globigerinelloides planktic foraminiferal assemblages, associated with sparse (typically <5%), mainly epifaunal benthic taxa and rare radiolarians. Commencing abruptly at the base of the boundary clay, maximum size of planktic and benthic specimens decreases sharply, while abundance of both radiolarian and benthic foraminifera increase about tenfold relative to planktics, features which typify the basal 0.4 m of Paleocene strata. Heterohelix/Hedbergella associations characterise planktic assemblages initially, but give way to Eoglobigerina /Chiloguembelina planktic assemblages. Epifaunal taxa dominate benthic faunas, but mfaunal forms show minor abundance peaks. Benthic abundance remains near 45% up through c. 0.3 m but then declines sharply to c. 25% at 0.40 m (highest detailed sample). Stratigraphically higher samples were studied in less detail. From 0.5 to 11.5 m they contain poor foraminiferal assemblages similar to those described above, but these are then replaced by planktic‐poor (<5% planktics) assemblages with normal‐sized benthic taxa, including Gavelinella beccariiformis and Nuttallides cretatruempyi, which occur to the top of the exposed section.

Species novae graminum Novae‐Zelandiae I

Newly recognised grasses are described in preparation for the publication of Flora of New Zealand, Vol. 5, the grasses: two are new dioecious species of Poa, P. schistacea widespread on scree slopes in western Otago and P. xenica of Nelson on screes below marble bluffs; cleistogamous Deyeuxia lacustris is known from one locality in north‐west Nelson and another in North Canterbury; Dichelachne lautumia is restricted to a limestone quarry near the mouth of the Flaxbourne River, Marlborough.

Search for fullerenes C 60and C 70in Cretaceous–Tertiary boundary sediments from Turkmenistan, Kazakhstan, Georgia, Austria, and Denmark

Fullerenes C 60and C 70have been found previously in sediments from the Cretaceous-Tertiary boundary (KTB) sites of Woodside Creek and Flaxbourne River (both New Zealand). Additional discoveries from Caravaca (Spain), Sumbar and Malyi Balkhan (Turkmenistan) and Stevns Klint (Denmark) are reported here. Fullerenes were not found in the KTB sediment from Elendgraben (Austria), nor in acid-demineralized sediments from Koshak (Kazakhstan) and Tetri Tskaro (Georgia). The average surface concentration of C 60at these sites is estimated to be 11.7×10 −3 g /cm 2(11.7 ng/cm 2), which implies 1.1 ppm normalized to the average elemental carbon surface concentration at KTB sites. Global wildfires following the Chicxulub impact 65 Myr ago are the most likely process by which these fullerenes were formed.

Search for extractable fullerenes in clays from the Cretaceous/Tertiary boundary of the Woodside Creek and Flaxbourne River sites, New Zealand

When fullerenes were first discovered to form spontaneously in condensing carbon vapors ( Kroto et al., 1985), it was suggested that they might be widely distributed in the Universe. Searches for fullerenes in meteorites (see Devries et al., 1993) were unsuccessful, but C 60 and C 70 were reported to occur on Earth in samples of shungite, a meta-anthracite from a deposit near Shunga, Russia ( Buseck et al., 1992), and in “fulgurite”, a substance formed when lightning strikes certain soils or rocks ( Daly et al., 1993). The occurrence of fullerenes in shungite is particularly surprising since fullerene synthesis in the laboratory has always involved gas phase chemistry at temperatures over 1000°C. Such conditions may be attained during lightning strikes, but shungite is believed to have formed from carbonaceous material creeping into fissures of a Precambrian rock which metamorphosed under extreme pressures. If the original carbonaceous material did not already contain fullerenes perhaps from wildfires, they must have formed during the metamorphism by as yet unknown solid- or liquid-phase mechanisms.

An iridium-rich calcareous claystone (Cretaceous-Tertiary boundary) from Wharanui, Marlborough, New Zealand

Abstract Abundances for iridium and 18 other elements were determined in samples from a Cretaceous-Tertiary (K-T) boundary sequence near Wharanui, Marlborough Province, South Island, New Zealand. Physical correlation and biostratigraphic evidence pinpointed a 20 mm layer of calcified boundary clay containing highly anomalous concentrations of indium (33 ng/g [ppb]) and other siderophiles such as nickel (497 μg/g [ppm]), chromium (140 μg/g), and cobalt (137 μg/g). Concentrations expressed on a decalcified (CaCO3-free) basis to avoid false anomalies caused by redissolution of carbonates after deposition are: 62 ng/g, 929 μg/g, 262 ng/g, and 256 μg/g, respectively. The integrated iridium deposition is 132 ng/cm2 after correction for background, and is almost exactly the same as the 134 ng/cm2 recorded for the Flaxbourne River K-T boundary sequence which is virtually complete. This indicates the probable completeness of the Wharanui sequence, though thorough paleontological confirmation will be difficult to o...

A new Cretaceous-Tertiary boundary site at Flaxbourne River, New Zealand: Biostratigraphy and geochemistry

An exceptionally complete rock sequence across the Cretaceous-Tertiary (K-T) boundary has been discovered near the Flaxboume River, Marlborough Province, South Island, New Zealand. The boundary is marked by a large Ir anomaly (21 ng/g on a decalcified basis), with an integrated abundance of 134 ng/ cm2 after correction for background. Above the boundary there is a 30 cm transition zone, in which a few Cretaceous foraminiferal taxa such as Hedbergella monmouthensis and Guembelitria cretacea survived, though with reduced abundance and size (only ca. 1 2 to 1 4 of normal), apparently reflecting environmental stresses. INAA and ICP analyses show that, in addition to Ir, the boundary clay is also enriched in Cr and Ni, mainly from meteoritic material, and As, Co, Cu, Sb, and Zn from terrestrial sources. Volcanic sources, even when scaled to the 10 7 km 3 volume of the Deccan basalts, fail by three orders of magnitude to account for the Ir and As at the K.-T boundary and by even larger factors for Sb, Zn, Cu, etc. Comparison of our data with those from six other K-T boundary sites shows that the Zn Sb , As Sb , and Zn As ratios generally fall between crustal and oceanic values, suggesting contributions from both sources. Mass balance calculations show that As and Sb could be derived from only 300–500 m of ocean water or also from modest amounts (20–36 g/cm 2) of average crustal rock. Copper and Zn, on the other hand, can only be derived from crustal or mantle rock (5–15 g/cm 2), presumably impact ejecta. Such an amount of ejecta is fairly close to the global fallout of boundary clay (2–5 g/cm 2).