Foraminiferal record of Holocene sea level

Collaborators: Roland Gehrels (University of Plymouth, U.K.)

Foraminiferal distribution in high tidal salt meadows and salt marshes is strongly zoned with respect to tidal elevation. This zonation can be used to estimate (using transfer functions or modern analogue technique) the tidal elevation at which fossil Holocene foraminiferal assemblages once lived. High resolution studies of fossil foraminiferal faunas in cores of salt marsh peat can be used to reconstruct changes in sea level over the last 500-1000 years.

Our pilot study in southern New Zealand indicated 35 cm sea-level rise in the last 130 years. For further studies around New Zealand, we are focussing on the tectonically more stable coastal areas in New Zealand away from the earthquake-prone plate boundary deformation zone.

Study areas

a. South Otago (Pounawea, Catlins Lake) - partly published, 2006; published 2008.
b. Tasmania - field work undertaken, 2006; in press, Gehrels led.
c. Southland (Mokomoko Inlet)- analyses underway, 2006-2009. Gehrels led
d. Eastern Southland (Waikawa Harbour) - analyses underway by PhD, Brigida Figueira, 2008-2011.
e. North-west Nelson (West Haven Inlet) - analyses underway by PhD, Brigida Figueira, 2009-2011.

f. Banks Peninsula (Akaroa Harbour) – analyses underway by PhD, Brigida Figueira, 2010-2011.

g. Christchurch (Heathcote Estuary) – analyses underway, 2011.

h. Auckland (Manukau Harbour) – analyses underway, 2011.
i. Subantarctic Islands (Auckland Island) - reconnaissance undertaken, 2004.

Publications

• Gehrels, W.R., Hayward, B.W., Newnham, R.M., and Southall, K.E., 2008, A 20th century acceleration in sea-level rise in New Zealand. Geophysical Research Letters 35: L02717, doi:10.1029/2007GL032632
  
• Southall, K.E., Gehrels, W.R., and Hayward, B.W., 2006. Foraminifera in a New Zealand salt marsh and their suitability as sea-level indicators. Marine Micropaleontology, 60: 167-179.
  
• Hayward, B.W., Grenfell, H.R., and Scott, D.B., 1999. Tidal range of marsh foraminifera for determining former sea-level heights in New Zealand. New Zealand Journal of Geology and Geophysics 42(3): 395-413.