Devonian sedimentary rocks have a limited outcrop in New Zealand. Two of the most important outcrops, however, occur in the Top of the South - in the Baton River valley to the west of Nelson, and in the Inangahua River Valley near Reefton. Outcrops in the Baton River Formation are confined to the upper reaches of the River Baton and its minor tributaries (e.g. Heine Stream). In the Reefton area, good outcrops occur in Lankey's Creek, Stony Creek and Yorkey Creek, as well as in Waitahu River.
Both formations are rich in fossils, but the fossil assemblages are distinct and only a very few species are common to both sequences. The two areas both date from the early Devonian, but there is some suggestion from the faunas that the Baton River deposits might be slightly older than those at Reefton. Their exact ages, however, are uncertain, because the brachiopod and bivalve evidence disagree to some extent. On the basis of the bivalves, the Baton River Formation might be assigned to the Lochkovian stage of the Devonian (419-412 m years BP), and the Reefton Formation to the Pragian to early Emsian stages (412-405 million years BP). On the basis of the brachiopods, the Baton formation is shifted slightly later, to the Pragian, and the Reefton deposits into the Emsian.
The depositional environments in which the rocks were formed also seem to have been somewhat different, and notably the two areas are on different terranes, so that they may have been much further apart at the time of deposition than they are now; they have been brought together by tectonic activity. In the Baton Valley, the sequence starts with a conglomerate, indicating a shallow-water environment. An abrupt change to deeper water conditions clearly occurred, however, and the rest of the sequence comprises mudstones with some shaley and sandy layers and rare beds of marble.In the Reefton area, the deposits comprise a series of mudstones, limestone and rarer sandstone and appear to represent a near-shore environment.
From various sources of evidence, New Zealand at this time (or that part of it represented by these deposits) seemed to lie between 30 and 40S of the Equator. The faunas from Baton River, especially, have been shown to be similar to those found at several sites in South East Australia; those from Reefton seem to be more endemic to New Zealand. However, the fauna in both areas is somewhat species-poor, so comparisons need to be made with care. It is possible that both areas nested close to SE Australia at the time of deposition.
The fossils represented in the collection come mainly from the Reefton area, where good exposures are more readily available. Many of the exposures in the Baton River Valley are within the Kauranghi National Park, so collecting fossil material is not permitted and the condition of fossils from this area is also often rather poor.
A full list of species recognised from the two areas is available here. This includes several species not represented in the collection.
To see more details of any of the fossils, click on the images below. For further reading, see the list at the bottom of the page.
Further Reading: Allan, R.S. 1945 Palaeozoic and Mesozoic brachiopod faunas in New Zealand: with an index to the genera and species. Transactions of the Royal Society of New Zealand 75 (1), 1-22. Allan, R.S. 1947 A revision of the Brachiopoda of the Lower Devonian strata of Reefton, New Zealand. Journal of Palanteology 21 (5), 436-452. Bradshaw, M. 1995 Stratigraphy and structure of the Lower Devonian rocks of the Waitahu and Orlando Outliers, near Reefton, New Zealand, and their relationship to the Inangahua Outlier. New Zealand Journal of Geology and Geophysics 38(1), 81-92. Bradshaw, M. 2000 Base of the Devonian Baton Formation and the question of a pre‐Baton tectonic event in the Takaka Terrane, New Zealand. New Zealand Journal of Geology and Geophysics 43(4), 601-610. Bradshaw, M.A. & Hegan, B.D. 1983 Stratigraphy and structure of the Devonian rocks of Inangahua Outlier, Reefton, New Zealand. New Zealand Journal of Geology and Geophysics 26(4), 325-344. Dowding, E.M. & Ebach, M.C. 2018 An interim global bioregionalisation of Devonian areas. Palaeobiodiversity and Palaeoenvironments 98, 527–547. Earp, C. 2016 Late Early Devonian brachiopods from Montys Hut Formation, central Victoria, Australia. Alcheringa: An Australasian Journal of Palaeontology 40(2), 161-181. Gill, E.D. 1952 Palaeogeography of the Australian-New Zealand region in Lower Devonian time. Transactions of the Royal Society of New Zealand 80(2), 171-185. Shirley, J. 1938 The fauna of the Baton River Beds (Devonian), New Zealand. Quarterly Journal of the Geological Society 94, 459-506.d. Strusz, D.L. et al. 1972 Correlation of the Lower Devonian rocks of Australasia.Journal of the Geological Society of Australia 18(4), 427-455. Willis, I. 1965 Stratigraphy and structure of the Devonian strata at Baton River, New Zealand. New Zealand Journal of Geology and Geophysics 8(1), 35-48.