John D. Collen

Shoreline Changes and Sediment Redistribution at Palmyra Atoll (Equatorial Pacific Ocean): 1874–Present

Abstract Reef islands of Palmyra Atoll in the northern Line Islands, equatorial Pacific Ocean, underwent mainly minor natural changes in shape and size between 1874 and 1940. Many major changes occurred between 1940 and 1945 when military construction created a dredged channel into the lagoon, enlarged several islands, joined most islands around the lagoon system into a continuous roadway, constructed a causeway separating two lagoons, and created several new islands. Overall, land area approximately doubled and land volume approximately trebled during this period, and the construction affected water circulation between reef flats and lagoons. Since 1945, the atoll has been largely uninhabited, construction and most maintenance of the newly-created shoreline has ceased, and coastlines of larger islands have simplified by infilling of bays and erosion of promontories, at net rates of up to 1.8 m/y. Narrower land masses have been broken into multiple smaller arcuate islands with intervening shallow channels. Sediment moves mainly westward along ocean coasts, into lagoons on lagoon coasts, and via tidal currents where causeways have been breached. In the east, Barren Island appeared and began growing from natural causes well before military construction. After purchase by The Nature Conservancy, the atoll was designated a U.S. National Wildlife Refuge in 2001. This protection offers the opportunity to observe coastal processes operating in the absence of the efforts to protect infrastructure typically associated with inhabited atolls.

Elemental Anomalies at the Cretaceous-Tertiary Boundary, Woodside Creek, New Zealand

Iridium and 26 other elements were determined in shale from the Cretaceous-Tertiary boundary at the locus classicus (for iridium anomalies) at Woodside Creek, New Zealand. Iridium, gold, copper, cobalt, chromium, nickel, arsenic, molybdenum, and iron were enriched in the basal 2 millimeters of the 8-millimeter shale parting as compared with the rest of the stratigraphic column. No other shale partings in the column had anomalous concentrations of any element when the data were expressed on a carbonate-free basis. The boundary material showed striking compositional similarities with the Stevns Klint Danish boundary shale. Elemental concentrations were in general much higher in the New Zealand material than in nonboundary shales from elsewhere in the world. The high concentration of iridium (153 nanograms per gram) in the basal layer of the boundary, together with the enrichment of other siderophile elements supports the idea of an extraterrestrial source for much of the material. The iridium/gold ratio of 2.1 is also in accordance with such a source. The iridium content of the basal layer is higher than for any other marine boundary shale obtained on land. The integrated iridium value is 187 nanograms per square centimeter of boundary surface.

Cytologic and Genetic Characteristics of Endobiotic Bacteria and Kleptoplasts of Virgulinella fragilis (Foraminifera)

The benthic foraminifer Virgulinella fragilis Grindell and Collen 1976 has multiple putative symbioses with both bacterial and kleptoplast endobionts, possibly aiding its survival in environments from dysoxia (5–45 μmol‐O2/L) to microxia (0–5 μmol‐O2/L) and in the dark. To clarify the origin and function of V. fragilis endobionts, we used genetic analyses and transmission electron microscope observations. Virgulinella fragilis retained δ‐proteobacteria concentrated at its cell periphery just beneath the cell membranes. Unlike another foraminifer Stainforthia spp., which retains many bacterial species, V. fragilis has a less variable bacterial community. This suggests that V. fragilis maintains a specific intracellular bacterial flora. Unlike the endobiotic bacteria, V. fragilis klepto‐plasts originated from various diatom species and are found in the interior cytoplasm. We found evidence of both retention and digestion of kleptoplasts, and of fragmentation of the kleptoplastid outer membrane that likely facilitates transport of kleptoplastid products to the host. Accumulations of mitochondria were observed encircling endobiotic bacteria. It is likely that the bacteria use host organic material for carbon oxidation. The mitochondria may use oxygen available around the δ‐proteobacteria and synthesize adenosine triphosphate, perhaps for sulfide oxidation.

A geochemical appraisal of oil seeps from the East Coast Basin, New Zealand

Abstract Oil seeps and stains from the East Coast Basin, New Zealand have been investigated using biomarker and stable carbon isotope analyses to determine oil-oil correlations. Oils sampled from the Raukumara Peninsula (northern East Coast Basin, North Island) and Marlborough (southern East Coast Basin, South Island) are derived from Late Cretaceous-Paleocene marine source rocks with a minor terrestrial content and are isotopically light. In contrast, oils sampled from Hawke’s Bay and Wairarapa (central and southern East Coast Basin, North Island) are derived from Paleocene marine source rocks, which contain high abundances of C30 regular steranes and 28,30-bisnorhopane, and are isotopically heavier than the other group. Biomarkers and bulk carbon isotopes show that there are at least two distinct sources of hydrocarbons in the basin.

Weathered spheroids in a Cretaceous/Tertiary boundary shale at Woodside Creek, New Zealand

Three types of spheroids are found in the iridium-rich shale layer at the Cretaceous/Tertiary boundary at Woodside Creek, South Island, New Zealand. Two of the types (A and B) consist mainly of microcrystalline goethite, whereas the third type (F) contains an appreciable quantity of hematite. There is a strong correlation between the iridium content of the spheroids and their matrices and the concentrations of other siderophiles such as chromium, cobalt, iron, and nickel. A similar pattern was observed for the chalcophiles arsenic, copper, and zinc. It is suggested that spheroids of types A and B are weathering products derived from diagenetic pyrite clumps and that type F, which contains hematite, represents a further stage in the weathering process and was derived from goethite. The original pyritic material could have readily scavenged arsenic and other siderophiles from the sea-water column under organic-rich reducing conditions at the end of the Cretaceous, and the siderophiles including iridium could have been incorporated into the original meteoritic material. It was concluded, therefore, that types A, B, and F spheroids are weathering products and do not represent original meteoritic material.

Comparison of aromaticity and phenolic content as parameters for characterization of coal by 13C n.m.r. spectroscopy

Cross-polarization and magic-angle spinning techniques were used to obtain 13C n.m.r. spectra of 27 New Zealand coals sampled from drill cuttings at depths between 1.4 and 4.0 km in the Tara-1 oil exploration well, offshore south of New Zealand. Aromaticity and phenolic content were estimated from each spectrum. Of these two parameters, the phenolic content showed a stronger correlation with depth. The correlation was improved further by expressing the phenolic content as a fraction of the aromatic content. It was concluded that a combination of these parameters provides a new method for obtaining information about differences both in depositional environments and in the extent of subsequent coalification for suites of coal samples.

Evidence for marine deposition in the Late Cretaceous Pakawau group, northwest Nelson

Abstract Marine sediments are described from the upper part of the Late Cretaceous (Haumurian) Pakawau Group, exposed in northwest Nelson, New Zealand. The Pakawau Group (onshore) has been previously considered to be entirely nonmarine, but sedimentological and micropaleontological analyses of the North Cape Formation have revealed sedimentary structures and microfossils indicative of marine sedimentation. The North Cape Formation, 300–400 m thick, consists of sandstones, conglomerates, and discontinuous fine‐grained units, but differs from surrounding strata by the absence of coal beds. Sedimentary structures in the North Cape Formation include mud‐draped cross‐bedding, bidirectional ripple cross‐laminations, and some bioturbation. Finegrained units contain late Haumurian marine dinoflagellates, which are commonly fragmented and abraded. The evidence suggests that North Cape Formation was deposited in a tidally influenced marginal‐marine, possibly estuarine, environment. Similar sandstone‐rich marine sed...

FLORESINA : A GENUS OF PREDATORS, PARASITES OR SCAVENGERS?

Hallock and Talge (1994) described a small predatory foraminifer Floresina amphiphaga attacking the larger foraminifer Amphistegina gibbosa . The attack by F. amphiphaga on A. gibbosa often resulted in the death of the latter and formed a characteristic trace on its test. We report a similar trace on the test of the planktonic foraminifer, Globorotalia menardii , from a sample from 175 m water depth, collected seaward of the barrier reef at Suva, Fiji, that may be the result of Floresina attack. If this supposition is correct, it suggests that drilling is more widespread in the genus that previously known; that the phenomenon may extend beyond alleged predation or parasitism of living foraminifera to scavenging on dead foraminifera; and that foraminfer-foraminifer interactions involving drilling may be more widespread than previously suspected.

The atmospheric lead record preserved in lagoon sediments at a remote equatorial Pacific location: Palmyra Atoll, northern Line Islands

Anthropogenic lead (Pb) inputs to the atmosphere increased greatly over the past century and now dominate Pb supply to the oceans. However, the Pb content of sediments across the equatorial Pacific region is relatively unknown, and data exist only for deep sea sites where Pb deposition lags surface water inputs by up to a century. Here we present ICP-MS analyses of Pb of a core from a lagoon at Palmyra Atoll, northern Line Islands, that spans approximately the past 160 years. The non-bioturbated sediments of the euxinic lagoon, coupled with rapid rates of deposition, provide a unique fine-scale record of atmospheric Pb supply at a remote Pacific location. These first observations of historic Pb sedimentation in an atoll lagoon reveal a 63-fold increase in Pb flux to sediments during the past century and correlate directly with the North American consumption of leaded gasoline that began in 1926.

Distant Storms as Drivers of Environmental Change at Pacific Atolls

The central Pacific Ocean with its many low lying islands and atolls is under threat from sea level rise and increased storm activity. Here, we illustrate how increasing frequency and severity of large scale storm events associated with global climate change may be particularly profound at the local scale for human populations that rely on lagoon systems for provision of a variety of goods and services. In August 2011 a storm originating in the Southern Ocean caused a large amplitude ocean swell to move northward through the Pacific Ocean. Its arrival at Palmyra Atoll coincided with transient elevated sea surface height and triggered turnover of the lagoon water column. This storm-induced change to the lagoon reflects long distance connectivity with propagated wave energy from the Southern Ocean and illustrates the increasing threats generated by climate change that are faced by human populations on most low-lying Pacific islands and atolls.