The Haumurian (=Maastrichtian) belemnite Dimitobelus hectori Stevens, used by Clayton and Stevens (1968) in obtaining paleotemperature data, occurs in relatively shallow inshore sites (Brighton Formation near Dunedin: Katiki Formation at Shag Point; and Laidmore Formation at Middle Waipara Gorge). This is deduced both from the sediments in which the belemnite occurs and from the accompanying foraminifera.

It is unlikely that the marine temperature prevailing at the time these sediments were deposited can be regarded as typical for the Haumurian sea as a whole. Foraminifera present in sediments which represent more offshore and deeper environments (e.g. Whangai Formation of southern Hawke's Bay and some Haumurian sediments in Raukumara Peninsula and Northland) include planktonic and benthonic taxa with probable warm-temperate affinities. While temperatures in the inshore areas (in which the belemnites occur) may have ranged between 14.2 and 16°C, as suggested by Clayton and Stevens, it seems probable (on microfaunal evidence) that the more offshore areas were affected by slightly warmer currents, with temperatures of up to 20°C or perhaps slightly more. This suggestion implies a moderately steep temperature gradient over a relatively short distance. Garner (1961) has shown that such gradients do occur today around the New Zealand coast. For instance, his figures 2 and 28 show section lines extending fifty to seventy miles out from and normal to the coast in which temperature elevations and depressions of between four and six degrees centigrade occur.

I would, then, accept the data offered by Clayton and Stevens as local data pertaining to restricted parts of the Haumurian sea. It is important to bear this point in mind when discussing New Zealand marine temperature data in relation to those from other parts of the southwestern and southeastern Pacific.

Late Cretaceous Marine Climates in the Southwestern and Southeastern Pacific

The Campanian-Maastrichtian microfaunas of this area are much less well-known than those of the northern hemisphere. It page 9 is instructive, however, to briefly consider the available data from Peru, Chile, the Scotia Arc, Grahamland, New Zealand, the Solomon Islands, and New Guinea. All these areas lie along the Circum-Pacific orogenic belt, with Cretaceous sediments in most instances taking the form of non-calcareous elastics. Calcareous sediments occur infrequently and limestones are confined mostly to the low latitude areas.

Examination of the geographic distribution of certain Campanian-Maastrichtian planktonic and calcareous benthonic foraminifera suggests a strong case for paleo-latitudinal zonation in the southern hemisphere.

Recent Chilean publications (Martinez-Pardo, 1965; Herm, 1966) indicate Campanian-Maastrichtian microfaunal compositions almost identical with those of New Zealand. In New Zealand, uppermost Cretaceous (Haumurian) microfaunas occur as far south as 46°S lat., but in Chile comparable faunas extend as far south as 53°S lat. Microfaunas from these high latitude localities include species of Bolivinoides, Heterohelix, Guembelitria, Rugoglobigerina, Globigerinelloides, Hedbergella, and Abathomphalus. Double-keeled Globotruncana is absent from these areas and seems to have been confined in its distribution to the low southern latitudes, although Macfadyen (1966) reports a single questionable occurrence from the Senonian of Grahamland. Double-keeled Globotruncana, Pseudotextularia, and the larger foraminifera Pseudorbitoides and Orbitoides are present in the uppermost Cretaceous in New Guinea, 5°S lat. (Glaessner, 1960). Senonian double-keeled Globotruncana are also present in the Solomon Islands, 8°S lat. (Coleman, 1966). The genus is also present in the Campanian-Maastrichtian of Peru, 4-5°S lat. (Weiss, 1955).

The distribution of late Cretaceous planktonic and certain smaller and larger calcareous benthic foraminifera in the peripheral regions of the south Pacific suggest the existence of two latitudinal zones; a narrow zone just south of the present equator in which Tethyan taxa occur, and a much wider zone extending from approximately 10°S lat., to at least 53°S lat., from which the above-mentioned lower latitude taxa appear to be absent. On the basis of the available evidence the writer interprets the distribution pattern as indicating tropical to sub-tropical marine temperatures in the low latitudes and warm to cool temperate conditions in the middle and high latitudes. There is no evidence for unduly cool marine climates in the high latitudes during the late Cretaceous. Future investigations in the south Pacific might be expected to reveal sporadic occurrences of Tethyan planktonic and benthonic foraminifera in the higher latitudes, suggesting occasional southward invasion of tropical or subtropical waters into the temperate zone. To date, however, such data are lacking.

Discussion

(Editors Note: No time was available for formal discussion after this paper).