Stilwell—Oldest volutes from early Paleogene


at 75°S–80°S during the Cenomanian-Turonian stages) to latitude ca. 54°S (R. Sutherland in Stilwell et al., 2006), and was totally separated from the Gondwana margin, and both terrestrial and marine fossil assemblages began to diverge concomitant with its isolation (see paleogeographic map, Fig. 5). There is evidence of some land at the K-Pg boundary in Zealandia, despite rising sea-levels, with the discovery of large numbers of fossil birds approximately 66–64Ma in the Chatham Islands (J.D.S. and J. Clarke, unpublished data).At the boundary global cooling ensued, but by late Paleocene-early Eocene time, the thermal event saw expansion of warm waters during this greenhouse interval and hottest time throughout the entire Cenozoic, with sub-tropical molluscs reaching eastern Zealandia (Beu and Maxwell, 1990; Stilwell, 2014). Since the dawn of the newmillennium, it has been recognized


that the Paleocene record is much more widespread in Zealandia than previously reported with fossiliferous assemblages spanning the Castle Hill Basin in CanterburytoWangaloa, southeastern OtagoinSouth Island and float boulders in the Kaiwhata River, southern North Island to eastern Zealandia in the Chatham Islands (as reviewed by Stilwell, 1994, 2003). The fossils described in this paper were collected from the Wangaloa and Abbotsford (‘Steel Greensand’) formations in Otago, and the Red Bluff Tuff, exposed on both Chatham and Pitt islands. The Wangaloa Formation (Fig. 2) atMeasly Beach and Mitchells Rocks is characterized by highly fossiliferous quartz sandstone and conglomerate ofmid-late


Danian age (c. 64–62Ma, age based on foraminiferans, dino- flagellates, and palynomorphs, see review by Stilwell, 1993, 2003, this work), which has been interpreted as being deposited in


33


near-shore environments such as shore-face or during sporadic storm conditions near fair-weather wave base and also tidal channel deposits (Lindqvist, 1986; Lindqvist and Douglas, 1987; Beu and Maxwell, 1990; Stilwell, 1993). Poorly fossiliferous assemblages of Paleocene molluscs and decapods have been collected from the Abbotsford Formation (also of Danian age with conspecific taxa found in the Wangaloa Formation), which also represent quite shallow marine conditions (Stilwell, 1994, 2003). The Red Bluff Tuff spans late Paleocene to early Eocene time, so these rocks are a bit younger than the Danian Wangaloa and Abbotsford formations. The Red Bluff Tuff (Figs. 3, 4) comprises approximately 100m of marine, calcareous palagonite tuff of basaltic composition with horizons of lapillistone and tuff-breccia and highly fossiliferous assemblages dated as spanning 53–48Ma based on recent radiometric datingbyNémethetal. (2013).The fossils reflectmostly shallowmarine, hard-ground substrates on the summits or flanks of volcanic sea-mounts in eastern Zealandia in subtropical waters at the height of the Paleocene-Eocene thermal event (Beu andMaxwell, 1990; Stilwell, 2014).


Significance of Paleocene Mollusca and new volutes from Zealandia


Collections of fossils made by the author from Mitchells Rocks, Wangaloa (Fig. 2), have resulted in the discovery of the oldest recorded volutes from the New Zealand region’s geologic record (Fig. 6). Collecting at Wangaloa since 1869 and commencing with a small collection by 19th century Scottish geologist James Hector (1834–1907) has not, until this report, produced volutid gastropods. Many large, in situ blocks of fossiliferous sandstone were collected by Pionjär rock drill/hammer and subsequently winched from the beach at Mitchells Rocks up and over a cliff, and taken originally to the laboratory at the University of Otago for analyses and subsequently to James Cook University and Monash University in Australia. Two new species, represented by two specimens collected from the same block, are present in ‘Wangaloan’


Figure 2. Coastal cliff section of the Wangaloa Formation at Mitchells


Rocks, Wangaloa, where the first Paleocene fossils from New Zealand were first collected by Sir James Hector in 1869. Note the shallow, tidal channel deposits, represented by concretionary, highly fossiliferous sandstones and strongly burrowed interval, characterized by anastomosing galleries of the ichnogenus, Ophiomorpha, made by a post-K-Pg extinction ghost shrimp (Callianassidae) during a dynamic phase of biotic rebound in the earliest Cenozoic. These deposits host a high diversity of invertebrates and vertebrates with more than 150 taxa recorded (Stilwell, 1993, 1994; Buchanan et al., 2007). The new and revised species of Wangaluta n. gen. and Alcithoe s.l. were discovered via intense, bulk sampling at this remote SE Otago locality.


Figure 3. Rocky Side, northwestern Pitt Island, Chatham Islands, where the new volute, Teremelon onoua n. sp., was collected in the Red Bluff Tuff (RBT); a view of the bay with red arrow pointing to the RBT in a slump section, where it rests disconformably upon the Upper Cretaceous (Campanian-Maastrichtian) Kahuitara Tuff.


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