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St Johns, New Zealand

Hayward B.W.,Geomarine Research
Journal of Foraminiferal Research | Year: 2014

Thirteen benthic foraminiferal species dominate modem " monospecific" faunas (dead faunas with >80% of one species in >63-pm samples) in New Zealand. These faunas occur in sheltered, often brackish, intertidal or shallow-subtidal environments, never deeper than 25 m. None occurs along exposed coasts or in the open ocean. Seven agglutinated species (Entzia macrescens, Haplophragmoides wilberti, H. manilaensis, Miliammina fusca, M. obliqua, Trochammina inflata, Trochamminita salsa) dominate " monospecific" faunas in salt marshes with varying salinity and elevational ranges. All but /. manilaensis have been recorded comprising 99-100% of at least one fauna. A further six species (Ammobaculites exiguus, Ammonia aoteana, Ammotium fragile, Elphidium excavatum clavatum, E. tvilliamsoni, E. gunteri) dominate "monospecific" faunas in unvegetated intertidal and shallow-subtidal (<3 m), sheltered estuary, inlet, or lagoon settings. "Monospecific" A mb. exiguus faunas are inferred to have been produced by dissolution of calcareous components. A further 17 species dominate modem near-monospecific faunas (50-80% of one species), 11 at depths <50 m and six in the open ocean at 504000-m depth. "Monospecific" and near-monospecific faunas are more common in higher latitudes, where overall species diversity is lower. Six species dominate "monospecific" early Miocene faunas in northern New Zealand: Elphidium crispum in a sheltered gravel beach; Nonionetla novozealandica in a deep-water (50100 m), possibly dysoxic harbour; and three larger, more robust species (Amphistegina aucklandica, Lepidocyclina orakiensis, Miogypsina intermedia) in current- or wave-concentrated beach or shallow-marine deposits. The only bathyal or abyssal "monospecific" fauna is dominated by Amphimorphinella butonensis occurring in a fossil hydrocarbon seep setting. Many of the modem " monospecific" faunas (especially those in salt marshes) are cosmopolitan whilst most of the fossil and some of the modem faunas are endemic to the New Zealand region. These high-dominance faunas are produced by taphonomic and ecological processes. Taphonomic causes include wave or current concentration by winnowing or transport in high energy shallow-marine environments and carbonate dissolution in low pH brackish salt marsh or deep-sea settings. Ecological drivers include highly specific adaptations that allow species to outcompete all others in stressful (intertidal) strongly variable (high-tidal brackish) or unusual (hydrocarbon seep) environments. Sometimes high test productivity of opportunistic species may result in near-monospecific faunas. Source


Hayward B.W.,Geomarine Research | Gregory M.R.,University of Auckland | Kennett J.P.,University of California at Santa Barbara
Geology | Year: 2011

Modern seafl oor hydrocarbon seeps are usually surrounded by an unusual macrobiota dominated by symbiont-bearing endemic bivalves and worms. Numerous species of foraminifera (shelled protists) also live around hydrocarbon seeps, but none have been found that are endemic to this environment. An extinct species of benthic foraminifera (Amphimorphinella butonensis) has been found in large numbers in a 15-m-diameter patch of siltstone surrounding a Miocene concretionary carbonate mound (inferred to be a fossil methane seep) in New Zealand. The tests exhibit highly negative δ 13C values, consistent with a methane-rich environment of recrystallization on or just below the seafl oor. This extremely rare species has been recorded only once before, from asphalt-impregnated Miocene muddy limestone in Indonesia, most likely also associated with hydrocarbon seepage. Is this the fi rst record of a foraminiferal species that was specifi cally adapted, and endemic, to hydrocarbon seep environments?. © 2011 Geological Society of America. Source


Mancin N.,University of Pavia | Hayward B.W.,Geomarine Research | Trattenero I.,University of Pavia | Trattenero I.,ENI S.p.A | And 2 more authors.
Marine Micropaleontology | Year: 2013

Over 100 cosmopolitan species of deep-sea benthic foraminifera (Extinction Group, Ext. Gp) became extinct during the late Pliocene-middle Pleistocene (3.6-0.55. Ma). Most had elongate, cylindrical tests and terminal apertures with complex modifications. This study provides new hypotheses on the functions of the morphologies that characterised the Ext. Gp and how these features could have been associated with their demise. From our functional morphological analysis we infer that: i) their elongate cylindrical or flabelliform tests, combined with fine perforations and a complex terminal apertural face are indicative of infaunal k-strategists with a low rate of metabolism; and ii) their complex apertural faces may also have been an adaptation for gathering or processing their specific phytodetrital food.We propose three alternative hypotheses for the cause of these extinctions, and where possible test them using our high resolution micropaleontological and geochemical record through the last 1.07Ma in lower bathyal site MD 97-2114 in the SW Pacific Ocean. Hypothesis 1 is that the Ext. Gp species were unable to adapt to increased variability in the overall quantity or pulsed seasonality of the food supply to the sea floor and were out-competed by opportunistic r-strategist benthic foraminifera. This is supported by the highly variable and increasing abundance of opportunistic foraminifera at our study site during the final phase of the extinction in the mid-Pleistocene Climate Transition, MPT. We doubt however, that there was increased variability in phytoplankton productivity throughout the world's oceans sufficient to bring about the global demise of the Ext. Gp. Hypothesis 2 is that lowered pCO2 during increasingly severe MPT glacials, which coincided with the final phases of the extinction, may have caused the decline and possible loss of the Ext. Gp's phytoplankton food source. Declining pCO2 during Neogene cooling was coeval with declining relative abundance of the Ext. Gp and reticulofenestrid nannofossils, but the final demise of this latter phytoplankton group occurred slightly later than the MPT in our study site and cannot be implicated with the extinction. If this hypothesis has any validity maybe the phytoplankton group left no fossil record. Our third alternative hypothesis is that maybe our Ext. Gp had much common DNA which made them the selective target of pathogens that caused their extinction. This does not easily explain their earlier disappearance at abyssal depths than at bathyal depths in our study region, which can be accommodated by hypotheses 1 and 2. © 2013 Elsevier B.V. Source


Bostock H.C.,NIWA - National Institute of Water and Atmospheric Research | Hayward B.W.,Geomarine Research | Neil H.L.,NIWA - National Institute of Water and Atmospheric Research | Currie K.I.,University of Otago | Dunbar G.B.,Victoria University of Wellington
Deep-Sea Research Part I: Oceanographic Research Papers | Year: 2011

We have compiled carbonate chemistry and sedimentary CaCO3% data for the deep-waters (>1500m water depth) of the southwest (SW) Pacific region. The complex topography in the SW Pacific influences the deep-water circulation and affects the carbonate ion concentration ([CO32-]), and the associated calcite saturation horizon (CSH, where ωcalcite=1). The Tasman Basin and the southeast (SE) New Zealand region have the deepest CSH at ~3100m, primarily influenced by middle and lower Circumpolar Deep Waters (m or lCPDW), while to the northeast of New Zealand the CSH is ~2800m, due to the corrosive influence of the old North Pacific deep waters (NPDW) on the upper CPDW (uCPDW). The carbonate compensation depth (CCD; defined by a sedimentary CaCO3 content of <20%), also varies between the basins in the SW Pacific. The CCD is ~4600m to the SE New Zealand, but only ~4000m to the NE New Zealand. The CaCO3 content of the sediment, however, can be influenced by a number of different factors other than dissolution; therefore, we suggest using the water chemistry to estimate the CCD. The depth difference between the CSH and CCD (δZCSH-CCD), however, varies considerably in this region and globally. The global δZCSH-CCD appears to expand with increase in age of the deep-water, resulting from a shoaling of the CSH. In contrast the depth of the chemical lysocline (ωcalcite=0.8) is less variable globally and is relatively similar, or close, to the CCD determined from the sedimentary CaCO3%. Geochemical definitions of the CCD, however, cannot be used to determine changes in the paleo-CCD. For the given range of factors that influence the sedimentary CaCO3%, an independent dissolution proxy, such as the foraminifera fragmentation % (>40%=foraminiferal lysocline) is required to define a depth where significant CaCO3 dissolution has occurred back through time. The current foraminiferal lysocline for the SW Pacific region ranges from 3100-3500m, which is predictably just slightly deeper than the CSH. This compilation of sediment and water chemistry data provides a CaCO3 dataset for the present SW Pacific for comparison with glacial/interglacial CaCO3 variations in deep-water sediment cores, and to monitor future changes in [CO32-] and dissolution of sedimentary CaCO3 resulting from increasing anthropogenic CO2. © 2010 Elsevier Ltd. Source


Mancin N.,University of Pavia | Basso E.,University of Pavia | Lupi C.,University of Pavia | Cobianchi M.,University of Pavia | Hayward B.W.,Geomarine Research
Marine Micropaleontology | Year: 2015

The agglutinated foraminiferal content from the last 550. kyr record of the IMAGES core MD 97-2114 (Chatham Rise, New Zealand) was analysed in order to detect the possible linkage existing between the composition of the grains forming the agglutinated tests and the deposition of tephras. The core was collected east of New Zealand, about 680. km from the active Taupo Volcanic Zone (TVZ) located on the North Island, thus it contains numerous macro- and microscopic tephra layers.Scanning Electron Microscopy and Energy Dispersive Spectroscopy analyses were carried out on entire agglutinated foraminifera as well as on sectioned specimens, sampled around and within the tephra layers. The analyses show that the studied foraminifera built structurally complex tests picking and selecting mineral and biogenic particles on the basis of their availability and abundance in the substratum, as well as their composition, size and shape. In most of the studied species, belonging to the order Textulariida, the composition of the agglutinated grains does not change when the deposition of the tephra layer strongly enriched the substratum in volcanic glass shards. Only the species Karreriella novangliae changed significantly its grain composition, mostly selecting volcanic glass fragments to cover the test surface. Nevertheless, the tephra deposition seems to influence the wall microstructure of the agglutinated tests. Textulariid specimens coming from the volcanoclastic layers have a thinner wall which is also characterised by a less abundant calcareous matrix with respect to the specimens sampled above or below the tephra layer.We hypothesise that the volcanic ash deposition probably interfered with the normal agglutinating process by causing the development of more aggressive waters at the sea floor which, in turn, could have induced carbonate dissolution. Our observations therefore suggest that the sediment type of the substratum is not the only controlling factor in the construction of the agglutinated foraminiferal test and grain selection, which appears to be species-dependent. © 2015 Elsevier B.V. Source

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