FNZ 68 Supplementary data - Simuliidae (Insecta: Diptera) - Early Palaeogeological aspects
Craig, DA; Craig, REG; Crosby, TK 2012. Simuliidae (Insecta: Diptera). Fauna of New Zealand 68, 336 pages.
(
ISSN 0111-5383; no. 68 (print),
ISSN 1179-7193 (online)
;
no.
68.
ISBN 978-0-478-34734-0 (print),
ISBN 978-0-478-34735-7 (online)
).
Published 29 Jun 2012
ZooBank:
Early Palaeogeological aspects of New Zealand: Gondwana to Oligocene
Two hundred million years ago (Jurassic) a sliver of land, part of which eventually formed New Zealand, lay along the eastern edge of Gondwana. This was Zealandia and is thought to have extended north of what is now Australia, incorporated New Caledonia, and continued south along what was to become West Antarctica.
Before 110 Mya (Middle Cretaceous) the eastern edge of Gondwana had a proto-Pacific Plate subducting beneath the super continent. Compression of sediments from the associated trench produced mountains (Rangitata Orogeny) along what is referred to as the New Zealand Arc. What would become the present Campbell Plateau lay between these mountains and West Antarctica. Towards the end of the Cretaceous (90–83 Mya), a spreading zone to the west, which eventually produced the Tasman Sea, and one farther south in West Antarctica, the Ross Sea, began separating Zealandia from the remnants of Gondwana.
Campbell Plateau and Great South Basin. The origin and subsequent history of the Campbell Plateau has been subjected to considerable recent investigation (e.g., Michaux & Leschen 2005; Zhu et al. 2006; Grobys et al. 2009; Sutherland et al. 2010; Spasojevic et al. 2010). The focus in part is to understand anomalous characteristics of the Plateau, namely, the unusual bathymetry of the Campbell Plateau and Ross Sea. Originally contemporaneous and adjacent, the Ross Sea is shallower than expected and the Campbell Plateau some 0.5–0.9 km deeper than normal for such plateaus, the latter having a thinner continental crust than other such structures. The Plateau is invoked in biogeographic scenarios regarding New Zealand biota (e.g., Michaux & Leschen 2005).
It has been suggested that the Campbell Plateau originated in the Early Cretaceous, prior to the breakup of Gondwana, consistent with other events at 130 Mya (mid Early Cretaceous). To account for the shallower Ross Sea and deeper Campbell Plateau, a hot mantle upwelling under the Ross Sea has been proposed as the proximate mechanism initiating that early rifting (Spasojevic et al. 2010, Sutherland et al. 2010).
The first splitting movement may have been a syncline rift that initially opened the Bounty Trough and then the Great South Basin. The Pacific–Antarctic Ridge then became active some 400 km towards Antarctica between the then Campbell Plateau and Marie Byrd Land. With active seafloor spreading occurring, New Zealand and the Campbell Plateau moved north away from the Antarctic Plate with a slight counter-clockwise motion. About 76 Mya, the formation of the Bellingshausen microplate to the east exacerbated the counter-clockwise rotation. These movements are well illustrated by Sutherland et al. (2010) and Spasojevic et al. (2010), while Eagles et al. (2004) provided a high resolution animated reconstruction of these events between 90–45 Mya and is recommended viewing. The present distribution of the various spreading zones, terranes, and microplates involved are well illustrated by McLoughlin (2001).
Since breakup of Zealandia from the West Antarctic, northward movement by the Campbell Plateau of some 2 600 km during the last 80 My has rotated the region some 90 degrees counter-clockwise. This has caused extensional thinning of the crust and moved it off the hot mantle upwelling. Sutherland et al. (2010, their Fig. 2) and Spasojevic et al. (2010) considered that movement off the hot upwelling, and less so the thinning, to have resulted in marked, rapid subsidence of the Campbell Plateau between 70–40 Mya (very Late Cretaceous–Mid Eocene), since when it has been stable. The aberrant shallow depth of the Ross Sea is considered to still involve the hot mantle plume.
Even more detailed modeling of the subsidence history of the Campbell Plateau is given by Zhu et al. (2006) where they suggested marine transgression of the Plateau commenced as early as the Late Cretaceous (80 Mya) and culminated in the Oligocene (34–23 Mya), more recent than proposed by Sutherland et al. (2010) and Spasojevic et al. (2010).
Of relevance to simuliids and other biota on Auckland and Campbell Islands, is that the intraplate volcanism that formed the islands had not yet occurred. Unlike the subsequent history of the current New Zealand landmass, which underwent major tectonic uplift, sediments from the Campbell Plateau of Eocene age and later indicate that the plateau has been geologically quiescent since then, apart from formation of the subantarctic islands.
Not often considered by biogeographers is the Great South Basin (Fig. 518), a massive sediment-filled depression off the southeast coast of the South Island (Cook et al. 1999). It starts northeast of Dunedin, then extends some 570 km southwest towards Auckland Islands, and eastwards 250 km to the Pukaki Rise, central on the Campbell Plateau (not shown in Fig. 518). The basin shows poorly with bathymetry, but is defined by 7–8 km depth of sediment, underlain by Cretaceous granites. Analysis of that sediment (e.g., Grobys et al. 2009) suggests an origin (opening) of a marine basin at 86.5 Mya and is generally considered to be the original syncline rift between Zealandia and West Antarctica. About 83.5–55.5 Mya analysis of drill cores suggests rapid deepening of the basin and filling with sediment.
The extent of land connection between the Campbell Plateau and the south of New Zealand are arguable, but Cook et al. (1999) modelled this extensively from mid Late Cretaceous (90 Mya) to the Present. They suggested that at 90 Mya, the Campbell Plateau, Challenger Plateau (to the west), Chatham Rise, and proto-New Zealand were all connected. By 70 Mya (very Late Cretaceous), the Bounty Trough and the Great South Basin were intruding onto this land. By 52 Mya (Early Eocene) the Campbell Plateau was submerged, but land still extended south of the present Stewart Island and slightly west onto the Challenger Plateau. At 30 Mya (mid Early Oligocene) the eastern side of the current South Island was a shallow marine shelf, but Stewart Island was still fully connected to the backbone of New Zealand. Campbell & Hutching (2007), however, noted that the island was submerged at 23 Mya (very early Miocene). By 10 Mya (middle Late Miocene) a recognisable configuration of New Zealand had been achieved, and Stewart Island connected.
New Zealand mainland. There has been major deformation of the portion of Zealandia that now comprises mainland New Zealand. For example, some models show that in the Middle Eocene (40 Mya), the eastern side of the South Island was near the same latitude as the northern part of the then North Island. The formation of present New Zealand is the result of movement along intraplate boundaries, namely the Pacific and Australian Plates; movements that amount to over 1 000 km. Fleming’s famous outlines of New Zealand land for those times have been shown to have little basis. However, he is not alone. King (2000) plotted some 14 reconstructions of exposed land of the North Island at 40 Mya. There is little concordance among outlines of the reconstructions. The same can be said for reconstructions for the South Island for various times. Indeed, Cook et al. (1999) noted that placement of current outlines of New Zealand on their own reconstructions must be considered approximations. A somewhat skeptical attitude is required when reviewing such models.
The Paleocene and Eocene (65–35 Mya) were a geologically quiet time for proto-New Zealand and it is generally thought that erosion peneplained the land and New Zealand was reduced to a series of low archipelagos. However, other evidence such as the Waipounamu Erosion Surface (Landis et al. 2008) indicates that New Zealand was flattened by marine transgression, not peneplained. The occurrence of widespread limestone has been interpreted to mean that during the Oligocene (34–23 Mya), New Zealand was completely submerged — the “Oligocene Inundation”, or “Great Drowning” as it is sometimes known. This assertion is hotly contested, with strong biological evidence for both sides. That is, some of New Zealand’s biota (e.g., the reptile Sphenodon, Leiopelma frogs, oligochaetes, and the onychophoran velvet worms) is such that dispersal from elsewhere onto re-emerging land following the Oligocene Inundation seems implausible. This is backed up by molecular studies that indicate some New Zealand biota diverged from their Gondwanan relatives about the time Zealandia split from the super continent. On the other hand there is good molecular evidence that indicates some members of New Zealand’s biota postdate any inundation. Further, vertebrate fossils of Miocene age from St Bathans in the South Island would require considerable land area prior to that, namely, during the Oligocene. High conifer diversity in the Oligo-Miocene of New Zealand also supports considerable land being present at that time (Jordan et al. 2011), so complete inundation does not appear to have occurred.
References
Campbell, H.; Hutching, G. 2007: In search of ancient New Zealand. Penguin Books and Geological and Nuclear Sciences, Wellington. 239 pp.
Cook, R. A.; Sutherland, R.; Zhu, H.; and others. 1999: Cretaceous–Cenozoic geology and petroleum systems of the Great South Basin, New Zealand. Institute of Geological and Nuclear Sciences Monograph 20: 1–188.
Eagles, G.; Gohl, K.; Larter, R. D. 2004: High resolution animation reconstruction of the South Pacific and West Antarctic Margin. Geochemistry, Geophysics, Geosystems 5: 21 pp. (doi:10.1029/2003GC000657)
Grobys, J. W. G.; Gohl, K.; Uenzelmann-Neben, G.; Davy, B.; Barker, D. 2009: Extensional and magmatic nature of the Campbell Plateau and Great South Basin from deep crustal studies. Tectonophysics 472: 213–225.
King, P. R. 2000: Tectonic reconstructions of New Zealand: 40 Ma to the Present. New Zealand Journal of Geology & Geophysics 43: 611–638.
Landis, C. A.; Campbell, H. J.; Begg, J. G.; Mildenhall, D. C.; Paterson, A. M.; Trewick, S. A. 2008: The Waipounamu Erosion Surface: questioning the antiquity of the New Zealand land surface and terrestrial fauna and flora. Geological Magazine 145: 173–197.
Jordan, G. J.; Carpenter, R. J.; Bannister, J. M. Lee, D. E.; Mildenhall, D. C.; Hill, R. S. 2011: High conifer diversity in Oligo-Miocene New Zealand. Australian Systematic Botany 24: 121–136.
McLoughlin, S. 2001: The breakup history of Gondwana and its impact on pre-Cenozoic floristic provincialism. Australian Journal of Botany 49: 271–300.
Michaux, B.; Leschen, R. A. B. 2005: East meets west: biogeology of the Campbell Plateau. Biological Journal of the Linnean Society 86: 95–115.
Spasojevic, S.; Gurnis, M.; Sutherland, R. 2010: Inferring mantle properties with an evolving dynamic model of the Antarctic–New Zealand region from the Late Cretaceous. Journal of Geophysical Research 115 (Solid Earth): B05402, doi: 10.1029/2009JB006612 pp16.
Sutherland, R.; Spasojevic, S.; Gurnis, M. 2010: Mantle upwelling after Gondwana subduction death explains anomalous topography and subsidence history of eastern New Zealand and West Antarctic. Geology 38: 155–158.
Zhu, H.; King, P. R.; Wood, R. A. 2006: Reconnaissance seismic mapping of the Late Cretaceous–Early Cenozoic foundering and regional marine onlap of the Campbell Plateau. Pp. 11 in New Zealand Petroleum Conference Proceedings 2006. Ministry of Economic Development Wellington.