31 Marine sandstone with turret shells galore
Mollusca, Gastropoda: Zeacolpus sp.
Measley Beach near the coastal South Otago settlement of Wangaloa has been recognised as a fossil hotspot since the geologist James Hector made a small collection of molluscs in the area in 1869. These and many other marine invertebrates, as well as some vertebrates and fossil wood, have been collected over the years from the fossil-rich Wangaloa Formation, a well-cemented quartz sandstone that was deposited in shallow seas, possibly in an inner shelf setting, and with storm-influenced deposits. There are many places within the Wangaloa Formation where shells are concentrated, but these shellbeds don’t form a continuous layer throughout the sedimentary horizon. These shell-rich spots can be seen in the cliffs and on the beach. In places, there are Teredo-bored logs of araucarian wood and many trace fossils including burrows of shrimp fossils known as Ophiomorpha.
Large block of sediment containing Zeacolpus turret shells, the long shells were aligned by a tidal current while resting on the ancient sea floor. A single large fossil Zeacolpus shell. Image credit: RE Fordyce. |
These rocks and fossils were deposited around 63 to 61 million years ago during the Paleocene, not long after the major extinction event at the end of the Cretaceous which wiped out the non-avian dinosaurs, marine reptiles such as mosasaurs and plesiosaurs, and molluscs such as ammonites and belemnites. So, the fossils at Wangaloa are of particular interest as they represent the survivors who made it through to the Cenozoic.
Some beds are covered with huge numbers of turret-shaped turritellid gastropods which are aligned by current activity but many other invertebrate fossils are present. They include dozens of large bivalves such as Lahillia and Glycymerita and gastropods such as Conchothyra and Globisinum. Some of the species found at Wangaloa have close relatives in rocks of similar age in the Antarctic Peninsula but others are found nowhere else. Other fossils include shark teeth, a small toothplate of a chimaeroid fish (sometimes known as ghost sharks) and rare fragments of turtles.
A large boulder collected from a shellbed at Measley Beach is set on a plinth in the Quadrangle outside the Department of Geology Building. It shows dozens of turritellid gastropods, mostly Zeacolpus.
—Written by Daphne E Lee
| Specimen number: OU 47954 (block), OU 47985 (shell) | Age: Approximately 62 million years old (Paleocene, early Teurian stage)(block), Approximately 23 million years old (late Oligocene to early Miocene, Waitakian stage)(shell) |
| Locality: Wangaloa, South Otago (block), Hakataramea Quarry (shell) | Rock Formation: Wangaloa Formation (block), Otekaike Limestone (shell) |
| Collected by: Unknown collectors | |
| Citation: Marwick J. 1971. New Zealand Turritellidae related to Zeacolpus Finlay (Gastropoda). New Zealand Geological Survey Paleontological Bulletin 44:1–87. | |
Evidence of life from a past geological age. Remains like bones, shells or wood, or an impression like a footprint, or some other evidence of life, from something that was alive more than 11,700 years ago.
The extended margin of a continent which is submerged under relatively shallow seas. While the width of the shelf varies between continents, most shelf seas are generally less than 100 metres deep.
A layer of sedimentary rock with distinct characteristics.
A family of conifer trees. A living example of an araucarian is kauri, Agathis australis.
Evidence of an organism from a past geological age but not the preserved remains of the organism itself.
66 to 56 million years ago.
A mass extinction event that occurred around 66 million years ago. An asteroid impact is generally considered to have been the cause.
145 to 66 million years ago.
All dinosaurs except birds. Examples include Deinonychus antirrhopus and Tyrannosaurus rex.
