Deciphering New Zealand's geological and environmental history using foraminiferal microfossils - ocean currents, human impacts, sea level rise, and earthquakes.
by Bruce W. Hayward, Geomarine Research, Auckland
For the past 70 years, microscopic fossil shells of foraminifera (marine, shelled, amoeba-like protists) have been best known for their value in dating New Zealand's widespread marine sedimentary rocks. In recent years however, fossil foraminifera have been used in an increasingly diverse range of studies documenting the history of past environments. Five New Zealand examples of such studies will be presented:
1. Planktic foraminiferal faunas provide a record of sea surface temperatures in three localities east of Canterbury over the last 1 million years. From this, movements of surface water currents and the subtropical convergence are inferred.
2. Deep-sea benthic faunas provide the history of depth changes in the Taranaki sedimentary basin over the last 30 million years, and these can be related to plate tectonic forces and sediment supply.
3. Estuarine foraminifera preserved in mud around the fringes of the Auckland's Waitemata Harbour indicate that the most significant factor impacting the harbour's ecology in human times has been the increase of freshwater runoff resulting from early European forest clearance and urban growth of impervious surfaces.
4. High-tidal foraminifera in salt marsh peat in South Otago indicate 20 cm of sea level rise since 1860, consistent with Dunedin tide gauge readings since 1900.
5. Foraminifera in sediment cores from Ahuriri Inlet, Napier, document seven major earthquakes in the last 7200 cal years, resulting in 8.5 m of subsidence, followed by 1.5 m of uplift during the 1931 Napier Earthquake.
Supporting lecture (University centres)
The Last Global Extinction in the Deep Sea, during the mid-Pleistocene Climate Transition
The last episode of enhanced global extinction in the deep sea is recorded by the disappearance of nearly 100, mostly cosmopolitan, bathyal and abyssal species of elongate benthic foraminifera, starting in the latest Pliocene and peaking during the mid-Pleistocene Climatic Transition (MPT, 1.2-0.6 Ma). The decline and disappearances began first in deeper southern hemisphere sites bathed by southern-sourced water (c. 2.5 Ma and 1.6 Ma) then later, in the MPT in northern-sourced deep water and southern- and northern-sourced intermediate water sites. This pattern parallels the glacial expansion of first the Antarctic ice sheet (late Pliocene), then later the North Atlantic ice sheet with consequent enhancement of the production of first deep water and later intermediate waters. This coincidence in timing suggests that causes of the extinctions were related to glacial changes in properties of the deep water masses (such as decreased temperature, increased dissolved oxygen) accompanying equatorial shifts in their source areas. The specialised nature of the apertures of the foraminifera that became extinct may provide a clue to the cause. These apertures may be an adaptation to consuming a specific kind of food, such as dysoxic bacteria that may have been killed off during the increasingly severe glacials over this period.
Biographical notes, Bruce Hayward
1975: PhD, Geology of Waitakere Ranges (early Miocene submarine volcano)
1976: Post Doc on foraminiferal microfossils, Smithsonian Institution, Washington, DC
1978-1991: Foraminiferal micropaleontologist, NZ Geological Survey, Lower Hutt
1991-1997: Curator of Marine Invertebrates, Auckland Museum
1998-2000: James Cook Research Fellow, University of Auckland
1997-present: Self-employed principal scientist of team studying foraminiferal micropaleontology, based at Auckland University and since 2003 at independent Geomarine Research premises, St Johns, Auckland.
1991-present: FRST-funded research on New Zealand foraminiferal microfossils
1999-2006: Marsden-funded research on foraminifera and SW Pacific paleoceanography and the last global extinction (subject of support lecture).
2006: Queen's Birthday honours list. Made Member of the New Zealand Order of Merit for services to Earth Science and Conservation.
Bruce developed an interest in the use of foraminifera for reconstructing past environments during his PhD and this has been the main thread of his and his team's research ever since. He has published numerous scientific papers, monographs and 10 books for the general public, including three Geological Society Guidebooks, and also last year's 50th anniversary history of the Geological Society of NZ.