Ninth international conference on - Marum

Abstracts of oral presentations 45
more common on longer time scales than we have observed. Both sites are covered with dense fields of shell
debris and with local sponges and/or soft tissue corals in association with carbonate platforms. Only at the LM-3
site, which consists of a large carbonate platform, live clams occur, often in association with tube worms (Fig.
1). Sediment-temperature measurements, in both areas, were largely comparable with the bottom-water
temperature except for one LM-3 site that was densely populated by polychaetes, where anomalous low
sediment-temperature was measured (Fig. 1).
Fig. 1: Screenshots taken from the ROV footage; clams and tubeworms at the carbonate platforms of the LM-3
site, sediment-temperature measurement at a ‘raindrop site’ (LM-3) and bubble release at a ‘raindrop site’ (Faure
Site).
Fig. 2: Screenshots taken from the ROV footage, showing the temporal variability of bubble release at the Faure
Site.
The analysis of the ROV data together with the integration of other datasets leads to a complete characterization
of the seep structure and environment which shows the real extent of the present active seep areas. Overall it is
clear that the present seeps areas are very confined in space and that the active seep sites have shifted in location
over time.
References:
Faure, K., Greinert, J., Pecher, I.A., Graham, I.J., Massoth, G.J., De Ronde, C.E.J., Wright, I.C., Baker, E.T. and
Olson, E.J., 2006. Methane seepage and its relation to slumping and gas hydrate at the Hikurangi
margin, New Zealand. N. Z. J. Geol. Geophys., 49, 503-516.
Henrys, S.A., Ellis, S. and Uruski, C., 2003. Conductive heat flow variations from bottom-simulating reflectors
on the Hikurangi margin, New Zealand. Geophys. Res. Lett., 30, 1065–1068.
Lewis, K.B. & Marshall, B.A., 1996. Seep faunas and other indicators of methane-rich dewatering on New
Zealand convergent margins. N. Z. J. Geol. Geophys., 39, 181-200.