Catherine M. Reid

Foraminiferal associations in Wanganui Bight and Queen Charlotte Sound, New Zealand

Abstract Eight benthic foraminiferal associations are recognised in Wanganui Bight and Queen Charlotte Sound, New Zealand, based on cluster analysis of census data from 52 sediment samples. Distribution of the four associations in Wanganui Bight correlates with increasing water depth: Elphidium charlottense/Haynesina depressula/ Patellinella inconspicua association (17–27 m); Patellinella inconspicua/ Quinqueloculina suborbicularis association (20–42 m); Cassidulina carinata/Miliolinella subrotundata association (42–66 m); and Cassidulina carinata/Bulimina submarginata (72–109 m). The four associations in Queen Charlotte Sound are: Quinqueloculina seminula/Elphidium advenum/Haynesina depressula in sandy shallows (0.5–7 m); Epistominella vitreal Haynesina depressula in shallows of the outer Sound (4–12 m); Elphidium vellai/Haynesina depressula in the mouth of the Sound (9–25 m); and Nonionella flemingi/ Notorotalia finlayi in a muddy, sheltered basin (25–42 m). The most important physical factors influenci...

Tsunami runup and tide-gauge observations from the 14 November 2016 M7.8 Kaikōura earthquake, New Zealand

The 2016 Mw 7.8 Kaikōura earthquake was one of the largest earthquakes in New Zealand’s historical record, and it generated the most significant local source tsunami to affect New Zealand since 1947. There are many unusual features of this earthquake from a tsunami perspective: the epicentre was well inland of the coast, multiple faults were involved in the rupture, and the greatest tsunami damage to residential property was far from the source. In this paper, we summarise the tectonic setting and the historical and geological evidence for past tsunamis on this coast, then present tsunami tide gauge and runup field observations of the tsunami that followed the Kaikōura earthquake. For the size of the tsunami, as inferred from the measured heights, the impact of this event was relatively modest, and we discuss the reasons for this which include: the state of the tide at the time of the earthquake, the degree of co-seismic uplift, and the nature of the coastal environment in the tsunami source region.

Sand volcanoes in the Avon–Heathcote Estuary produced by the 2010–2011 Christchurch Earthquakes: implications for geological preservation and expression

Abstract Sand volcanoes produced by liquefaction of saturated sands were widespread in the Avon–Heathcote Estuary following individual major events of the Christchurch 2010–2011 Earthquake sequence. Sand volcanoes were composed of fine grey sands and varied in diameter over the range 0.2–5 m, fed by vertical to subvertical feeder pipes of 15–25 cm diameter that cross-cut mud and shell horizons. Tides and wind-driven waves reduced, and at times removed, the profile of surface features; however, subsurface features remained unaffected. The geological signature of these volcanoes, formed in wet sandy tidally influenced settings such as estuaries, would be preservation of straight-sided feeder pipes 15–25 cm in diameter, >30 cm in length that cross-cut undeformed strata with or without expression of the erupted cone. Sediments were not able to be excavated beneath the shallow water table, and all observed feeder conduits occurred as roughly cylindrical pipes rather than elongated planar dykes; this does not preclude dykes being present deeper in the subsurface, however. Coseismic subsidence may enhance the preservation potential of surface features by increasing relative water depth, thereby increasing sedimentary accommodation space, and decreasing the influence of wave action in removing cones.

Environmental controls on the distribution of late Paleozoic bryozoan colony morphotypes: An example from the Permian of Tasmania, Australia

Abstract Paleozoic bryozoans differ significantly from modern forms in systematics and form, and in strength and occurrence of morphotypes. Nevertheless, the distribution of bryozoan morphotypes in modern oceans is often applied to the interpretation of fossil depositional environments. This study assesses the dominance of bryozoan morphotypes in the upper Paleozoic glaciomarine Tasmania Basin, and determines the environmental parameters that control their distribution by comparison with the environmental distribution and life habit of co-occurring brachiopod and bivalve biotas. Common Tasmanian late Paleozoic bryozoan morphotypes are erect-rigid fenestrate, erect-rigid branching, and erect-rigid foliose, with impersistent occurrences of encrusting forms. Water energy, or turbulence, is the primary control on bryozoan occurrence, with erect-rigid fenestrates occuring in low-energy settings, similar to reclining productid brachiopods, and erect-rigid foliose and branching forms in low- to moderate-energy settings, similar to nestling spiriferids. The secondary environmental parameter controlling bryozoan distribution is sediment accumulation rate. Both brachiopods and bryozoans need to keep their lophophores clear of sediment particles and are usually assumed to indicate low water turbidity. Differential epifaunal tiering, however, allows erect bryozoans to inhabit settings where sediment accumulation rates are sufficient to bury primary tier brachiopods at the sediment surface. With the caveat that water energy levels must remain at low-to-moderate levels, erect-rigid bryozoans are capable of dominating onshore settings where sedimentation rates may prohibit brachiopod dominance. The distribution of late Paleozoic bryozoan morphotypes examined here differs from modern distributions.

Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts

Biosiliceous sedimentary rocks are well known from the geologic record and many are correctly interpreted to have formed in deep-water or cold-water environments. Shallow non-polar spiculites are also known from the rock record, yet no modern analog has been documented for such environments. Bathurst Harbour, an estuarine system in southwest Tasmania, provides this much-needed modern analog. In this system a sharp halocline separates tannin-rich low-salinity surface waters from clear marine bottom waters. Tannins supply few nutrients and substantially reduce light penetration to bottom environments, resulting in a thinned photic zone and the mixing of deeper-water sub-photic biotas of soft corals, bryozoans, and sponges with other organisms more typical of this temperate shallow-water environment. The well-defined halocline allows a typically marine biota, including echinoderms, to live in bottom waters of this estuarine setting. The bioclastic factory, producing both carbonate and siliceous particles, exists in marine subphotic bottom waters of incised channel and shallow rocky environments along the shoreline. Extensive organic-rich soft sediments in protected embayments generate few bioclasts, but contain allochthonous sponge spicules transported from the adjacent bioclastic factory. Trapping of organic material within the estuarine system lowers sediment pH and promotes dissolution of carbonate biofragments, resulting in preferential preservation of siliceous sponge spicules. This situation implies that many biosiliceous neritic deposits in the rock record may be the result of similar preferential preservation.

Sedimentology and palaeoecology of lonestone-bearing mixed clastic rocks and cold-water carbonates of the Lower Permian Basal Beds at Fossil Cliffs, Maria Island, Tasmania (Australia): Insight into the initial decline of the late Palaeozoic ice age

Abstract The middle Sakmarian Basal Beds on Maria Island were deposited during the initial decline of the Late Palaeozoic Ice Age following Late Pennsylvanian–Early Sakmarian maximum glaciation. At that time, Tasmania was located within the South Polar Circle between an apparent ice-free pole (Antarctica) and the mid- to high-latitude Sydney-Bowen-Gunnedah glacigenic basins in eastern Australia. The dropstone-bearing Basal Beds consist of: interstratified siltstone, conglomerate and cold-water limestones of the Lower Erratic Zone; siltstone and Eurydesma-rich cold-water carbonates of the Darlington Limestone; and siltstone and conglomerate of the Upper Erratic Zone. Interstratification of the coarse-clastic strata, siltstones and limestones within these units were previously attributed to glacial/non-glacial cycles. However, the interfingering of beds within each of these units and the occurrence of large, fossil bryozoans crossing and abutting lithological boundaries indicate that cyclicity was of shorter duration than that of Milankovitch-driven cycles. Within these intertidal and subtidal deposits, the occurrence of rounded dropstones derived from local basement rocks exposed along a rocky coastline and an absence of glacial indicators other than dropstones, along with other evidence, suggest that ice rafting was by sea ice rather than by icebergs. Study results confirm the spatial restriction of Middle Sakmarian to earliest Wuchiapingian glaciation.

Reconsidering basin geometries of the West Coast: the influence of the Paparoa Core Complex on Oligocene Rift Systems

Oligocene and Miocene strata of the Nile Group are dominated by neritic cool-water carbonates formed within the Paparoa Trough along the western flank of the Challenger Rift System. In outcrop west of the Paparoa Range, the Nile Group contains three formations, the Waitakere Limestone, dominated by photozoan floatstone and grainstone facies, the Tiropahi Limestone, containing both impure heterozoan packstones and wackestones, and the Potikohua Limestone, consisting entirely of skeletal heterozoan grainstones. These correlative formations represent lateral depositional facies interpreted to record a submarine depression bounded by a northern irregular palaeohigh and a southern open marine plateau. It is proposed that these variations are the product of reactivation of structures associated with the underlying Paparoa Core Complex superimposed on the NE–SW rift axis emphasized within current basin models. This interpretation is consistent with exposures elsewhere in the West Coast region and highlights the need for palaeogeographic models of South Island to take older, rift-related basement structures into account.

Stratigraphy, paleontology, and tectonics of lower Miocene rocks in the Waipatiki/Mangatuna area, southern Hawke's Bay, New Zealand

Abstract Three lower Miocene units occur in the Waipatiki/Mangatuna area: Mangapuku Mudstone (Otaian), Westcott Sandstone (Otaian‐Altonian), and Tunakore Mudstone (Altonian). They are regarded as members of the Ihungia Formation and crop out mostly in the axis of the Waipatiki Syncline. Major faults near Toi Flat trend west‐east and, with an associated zone of minor faults, appear to thicken Westcott Sandstone in this area. Rocks showing gradual deepening from initially shallow water (Westcott Sandstone and Tunakore Mudstone) overlie those of deep‐water origin (Mangapuku Mudstone). Mangapuku Mudstone is a dark‐grey, calcareous, sandy mudstone with rare macrofaunas and diverse and abundant foraminiferal faunas of abyssal to shelf break origin. It is separated from older units by a deep‐water unconformity and was uplifted at rates of up to 1.1 km/m.y. to shallow‐water depths, with submarine erosion preceding deposition of Westcott Sandstone. Westcott Sandstone is dominated by grey, calcareous, fossiliferous...

The effect of volcanism on cool-water carbonate facies during maximum inundation of Zealandia in the Waitaki–Oamaru region

The paleogeography of the Waitaki–Oamaru region during the Oligocene–Miocene maximum inundation was defined by a volcanic paleohigh producing a rimmed cool-water carbonate shelf geometry. Basaltic surtseyan style cones became the setting for a productive cool-water carbonate factory isolated from terrigenous input. To the west, impure wackestones and calcareous siltstones contain terrigenous material derived from low relief landmasses farther to the west. A lowstand following the cessation of volcanism caused the paleohigh to become subaerially exposed, forming an extensive dissolution surface in the east correlative with submarine firmgrounds to the west. Stronger currents from the south and significant storm events sweeping over the high reworked carbonate and glauconitic sediment and deposited it in channels to the north. Carbonate deposition west of the paleohigh filled in the deeper part of the basin eventually resulting in a wider, shallower and more regular shelf environment. Depositional environments of the Waitaki–Oamaru region during the Waitakian (Late Oligocene–Early Miocene) were overall shallower than during the earlier Whaingaroan (Early Oligocene) Stage when a more complex paleotopography existed. This is unlike elsewhere in New Zealand where maximum depth was reached during the Waitakian Stage. Thus, the existence of an isolated, submerged paleohigh in a cool-water carbonate basin can have a significant effect on the evolution of that basin, stimulating carbonate factories to develop where they might otherwise not.

Large Sediment Encrusting Trepostome Bryozoans from the Permian of Tasmania, Australia

The Permian glaciomarine rocks of Tasmania contain unusually large trepostome bryozoan colonies that encrust soft sediments. These colonies have initially attached to hard substrates such as dropstones or brachiopod shells and have subsequently grown outwards across the sediment paleosurface. Specimen diameter is generally 150–350 mm, with one incomplete specimen with a radius of 400 mm. At least two species form this sediment encrusting morphology: Stenopora crinita Lonsdale 1845 and S. ovata Lonsdale 1844. Both of these species more commonly exhibit branching growth forms and the sediment encrusting forms are developed in offshore environments where slow sediment accumulation rates have allowed these low-profile colonies to flourish. This paper details the features of one well preserved 350 mm S. crinita specimen, along with a discussion of other material, and the significance of these forms with respect to depositional environment.