Patrick G. Quilty

Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans

From a synthesis of recent oceanic observations and paleo-data it is evident that certain species of giant diatoms including Rhizosolenia spp. Thalassiothrix spp. and Ethmodiscus rex may become concentrated at oceanic frontal zones and subsequently form episodes of mass flux to the sediment. Within the nutrient bearing waters advecting towards frontal boundaries, these species are generally not dominant, but they appear selectively segregated at fronts, and thus may dominate the export flux. Ancient Thalassiothrix diatom mat deposits in the eastern equatorial Pacific and beneath the Polar Front in the Southern Ocean record the highest open ocean sedimentation rates ever documented and represent vast sinks of silica and carbon. Several of the species involved are adapted to a stratified water column and may thrive in Deep Chlorophyll Maxima. Thus in oceanic regions and/or at times prone to enhanced surface water stratification (e.g., during meltwater pulses) they provide a mechanism for generating substantial biomass at depth and its subsequent export with concomitant implications for Si export and C drawdown. This ecology has important implications for ocean biogeochemical models suggesting that more than one diatom “functional type” should be used. In spite of the importance of these giant diatoms for biogeochemical cycling, their large size coupled with the constraints of conventional oceanographic survey schemes and techniques means that they are undersampled. An improved insight into these key species will be an important prerequisite for enhancing our understanding of marine biogeochemical cycling and for assessing the impacts of climate change on ocean export production.

Circum-Antarctic Coastal Environmental Shifts During the Late Quaternary Reflected by Emerged Marine Deposits

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.

Macquarie island and the cause of oceanic linear magnetic anomalies.

Macquarie Islands is formed of probably Pliocene oceanic crust. Intruded into pillow lavas is a belt of harzburgite and layered gabbro mnasses cut by dike swarms. Similar belt-like structures may cause the linear magnetic anomalies of the ocean.

Diatom biostratigraphy and age of the Pliocene Sørsdal Formation, Vestfold Hills, East Antarctica

Fossil marine diatom assemblages from the Sørsdal Formation, a deposit of diatomaceous sand from Marine Plain in the Vestfold Hills, provide age and palaeoenvironmental information from a Pliocene coastal setting in East Antarctica. Benthic and meroplanktic diatom taxa suggest deposition in a shallow coastal embayment with water depths of 20–25 m. Diatom biostratigraphy indicates that the Sørsdal Formation belongs to the Fragilariopsis barronii Zone (4.5 to 4.1 Ma), through correlation to reference sections in the Ross Sea and Southern Ocean. Features of the other biota suggest higher sea-surface temperatures and reduced sea-ice cover, consistent with global records of higher sea level.

Australodelphis mirus , a bizarre new toothless ziphiid-like fossil dolphin (Cetacea: Delphinidae) from the Pliocene of Vestfold Hills, East Antarctica

Australodelphis mirus (Delphinidae n. gen., n. sp) is a small extinct Early Pliocene dolphin known from five individuals from shallow-water strata of the Sørsdal Formation, Vestfold Hills, East Antarctica. Australodelphis mirus is the first higher vertebrate named from the Oligocene-Pleistocene interval on land in Antarctica, and is the first cetacean fossil from the polar margin of circum-Antarctic Southern Ocean that postdates the break-up of Gondwana. The dolphin is convergent in skull form with some living beaked whales (Mesoplodon spp.; Family Ziphiidae) in its long, narrow and toothless upper jaw and face, but skull suture patterns, basicranial sinuses, and ear-bones indicate close relationship with living long-beaked dolphins (Delphinidae). Australodelphis mirus perhaps was a suction-feeding squid-eater which occupied quiet near-shore shelf waters influenced by glaciers but probably lacking major sea-ice. Possible ecological equivalents of A. mirus (small ziphiids, long-beaked dolphins) do not occupy Antarctic waters today, perhaps excluded by cold conditions and/or sea-ice cover. Earlier Pliocene cetaceans worldwide reveal significant extinct and sometimes bizarre taxa, and extant families with ranges quite different from today, pointing to climate-related changes in cetacean ecology in the last 2–3 million years.

A review of the Cenozoic stratigraphy and glacial history of the Lambert Graben—Prydz Bay region, East Antarctica

The Cenozoic glacial history of East Antarctica is recorded in part by the stratigraphy of the Prydz Bay—Lambert Graben region. The glacigene strata and associated erosion surfaces record at least 10 intervals of glacial advance (with accompanying erosion and sediment compaction), and more than 17 intervals of glacial retreat (enabling open marine deposition in Prydz Bay and the Lambert Graben). The number of glacial advances and retreats is considerably less than would be expected from Milankovitch frequencies due to the incomplete stratigraphic record. Large advances of the Lambert Glacier caused progradation of the continental shelf edge. At times of extreme glacial retreat, marine conditions reached > 450 km inland from the modern ice shelf edge. This review presents a partial reconstruction of Cenozoic glacial extent within Prydz Bay and the Lambert Graben that can be compared to eustatic sea-level records from the southern Australian continental margin.

Cambrian and Ordovician dendroids and hydroids of Tasmania

Abstract All known Cambrian and Ordovician dendroids and hydroids of Tasmania are reviewed. Protohalecium hallianum Chapman & Thomas is revised at both generic and specific levels. Archaeocryptolaria recta var. flexilis Chapman & Thomas is revised to Protohalecium flexilis. Archaeolafoea serialis (Chapman & Thomas) (Hydroidea) is transferred to Mastigograptus (Dendroidea). The following species are described as new: Acanthograptus antiquus (Cambrian), A. banksi, Desmograptus thomasi (Ordovician).

Tertiary stratigraphy of Western Australia

Abstract This paper is a summary of the present knowledge of the Tertiary stratigraphy of Western Australia. Also included is new information on the Cainozoic of the Carnarvon Basin, a result of petroleum exploration in the area. Tertiary rocks formed during more than one cycle of deposition in three basins (Eucla, Perth, and Carnarvon), and also as thin units deposited in a single transgression along the south coast. The Tertiary stratigraphy of the Bonaparte Gulf Basin is not well known. Drilling in the Eucla Basin has encountered up to 400 m of Tertiary in the south central part, with uniform thinning towards the margins. The section begins with a middle‐upper Eocene carbonate unit which represents the dominant event in the Tertiary sedimentation in this basin. More carbonates were deposited in the late Oligocene‐early Miocene and middle Miocene. Along the south coast, the so‐called Bremer Basin, the Plantagenet Group (up to 100 m) of siltstone, sandstone, spongolite, and minor limestone, was deposited...

Cenomanian-Turonian and Neogene sediments from northeast of Kerguelen Ridge, Indian Ocean

Abstract Cenomanian-Turonian and Neogene calcareous sediments with rich foraminiferal faunas are recorded from USNS Eltanin Core E54-7, 500 km off the northeast flank of Kerguelen Ridge, southeast Indian Ocean. Surface waters in the vicinity were warm during the Cenomanian-Turonian and sediments accumulated at depths significantly deeper than expected on continental shelves but not in abyssal conditions. The Neogene fauna indicates cold surface waters. The initial break between Broken Ridge and Kerguelen Ridge must be older than late Cenomanian and not early Tertiary. The break probably coincides with early movement between Australia and Antarctica. Twenty-three planktonic foraminiferal species are recorded.

Stratigraphy of the Pliocene Sørsdal Formation, Marine Plain, Vestfold Hills, East Antarctica

The Sørsdal Formation and one member, Graveyard Sandstone Member constitute a sedimentary sequence covering approximately 10 km2 of Marine Plain, Vestfold Hills, East Antarctica. The new Formation consists dominantly of friable diatomaceous siltstone and sandstone with dark limestone lenses. It is in situ, essentially horizontal, 7.2 m thick in its type section and lies less than 25 m a.s.l. Graveyard Sandstone Member occurs near the top of the formation, is highly lithified sandy diamictite, 30–50 cm thick and widespread through the Marine Plain region. Using diatoms, the Formation is Early Pliocene in age (Fragilariopsis barronii, 4.5–4.1Ma). The Graveyard Sandstone Member probably was deposited during the Gilbert Chron interval (lower Chron 2Ar or C3n. 1r) of reversed magnetic polarity. The Sørsdal Formation contains fossil cetaceans and a diverse and well-preserved invertebrate fauna. Foraminifera are rare partly because of diagenesis, but include Ammoelphidiella antarctica. No evidence of coeval terrestrial vegetation has been recovered. The deposit accumulated in a series of small bays probably in an environment warmer than exists in the region today. There is no lithological evidence of glacial influence except in Graveyard Sandstone Member that may represent local glacial influence in a shallow marine to intertidal environment.