THE LATE JURASSICAMMONITE FAUNA OF NEW ZEALAND_2 pptx

PART 6. PALAEOECOLOGY FAUNAL SPECTRA The post-mortem drift of empty shells as observed in mod- em Nautilus (e.g. Kennedy & Cobban 1976; Saunders & Landman 1987; Ward 1987, 1988) has, at least theoreti- cally, the potential of distorting the relative proportions of ammonite taxa at specific stratigraphic horizons. How- ever, it is currently thought that in practice the effect of post-mortem drift is minimal and that therefore the faunal spectra derived from study of ammonite assemblages can provide a reasonably representative sample of ammonite populations and habitats through space and time (Westermann 1990, 1996b; Cecca 1992). A number of authors (e.g. Ziegler 1967; Kennedy & Cohban 1976; Westermann 1990, 1996b; Cecca 1992; Femandez-Lopez & Melendez 1996) have drawn atten- tion to the ecological differences between the two major groups of ammonites: the streamlined, smooth-shelled Leiostraca of the early ammonite literature (including no- tably the phylloceratids and lytoceratids) and the strongly ornamented Trachyostraca. Modem opinion envisages the Lejostraca as having been pelagic types, capable of living offshore and also of populating deep-shelf habitats (250- 300 m depth; Westermann 1990, 1996b) (see also Cecca et al 1990; Mouterde & Elmi 1991). However, as noted by Kennedy & Cobban (1976, p. 34) the local abundance of Leiostraca in clearly shallow-water deposits indicates that they were not entirely confined to deep-water situa- tions. By contrast, the Trachyostraca are generally con- sidered to have inhabited neritic shallow-water environ- ments (ca. 30-100 m depth, Westermam 1992). Following Ziegler (1967), the Late Jurassic ammonite as- semblages of New Zealand can be represented by means of spectra, illustrating the proportions of Leiostraca and Trachyostraca (Fig. 58). Ziegler (1967, fig. 12) proposed that the dominance of Leiostraca (in relation to Trachyostraca) at a specific stratigraphic level was indica- tive of deep water conditions (ca. 300-400 m depth). How- ever, as cautioned by Kennedy & Cobhan (1976 p. 34) "off-shore" rather than "deep-water9'perse may he a more appropriate appellation. Westermann (1990, 1996b) and Cecca (1 992) regard Leiostraca as pelagic, with the capa- bility of occupying deep water hahitats, in contrast to the - . neriiic shallow water Trachyostraca. Fernandez-Lopez & Melendez (1 996) have correlated increases in abundance of Leiostraca with changes accompanying eustatic rises in sea level. As may be seen from Fig. 58, in the New Zealand Late Jurassic sequence percentages of Leiostraca reach 55%, 56% and 50% in the Oraka Sandstone, Ohinerurn Forma- tion and Waibarakeke Conglomerate, respectively. These percentages may be interpreted as either indicating the presence of offshore (pelagic) influences or local post- mortem drift of otherwise pelagic ammonites (Tanabe 1979, p. 626; Cecca 1992, p. 265; Batt 1989, 1993). Sedimentological studies by Meesook (1989) indicate a generally deep water (= basin plain) origin for the Oraka and Ohineruru, and that of a deep water fan for the Waiharakeke. Thus the offshore explanation has perhaps greater validity. The remaining stratigraphic units, with percentages of Leiostraca ranging from 30% (Kowhai Point Siltstone) to 5% (Kinohaku Siltstone), are all clearly a reflection of shelf or upper slope habitats, as also indicated by Meesook's (1989) sedimentological analyses. The Takatahi Forma- tion, which lacks Leiostraca, is a major component of one of Meesook's coarse large volume fan cycles that prograded into the Kawhia basin during the Late Jurassic (see also Meesook & Grant-Mackie 1995). The changes in ammonite faunal spectra are thus a reflec- tion of a complex of changes: (i) changes in pelagic (off- shore) influence; (ii) sedimentological changes relating to the prograding development of fan systems; (iii) eustatic changes in sea level. Similar fluctuations in the propor- tions of Leiostraca and Trachyostraca, and presumably reflecting a similar interplay of environmental factors, have been documented by Sarti (1986) from Northern Italy, Wendt (1963) and Christ (1960) from West Sicily, Vigh (1 971) from Hungary, and Ceccaet al. (1990,1993), Cecca (1992) and Fernandez-Lopez & Melendez (1 996) from the Western Tethys (Fig. 59). LITHOLOGICAL CHANGES ACCOMPANYING LATE JURASSIC EUSTASY A lack of agreement on the precise overseas correlations to be applied to the Late Jurassic sequence o6New Zea- land has been a significant impediment to the application and testing of the recently proposed models of eustatic cycles (e.g. Haq et al. 1988). Although a study of eustatic influences was made by Stevens (1 990a), this was done in the absence of the refined correlations based on the am- monite faunas ofthis Bulletin. Nonetheless, Stevens noted changes in faunal diversity, first and last appearances, turnover and influxes of Tethyan taxa that were probably related to global eustatic changes. In Fig. 60 the eustatic models of Haq et al. (1988; with modifications by Strohmenger et al. 1991) and Hallam (1988, 1992) are matched with the standard lithological column of the Late Jurassic (using the Kawhia and Port Waikato sequences as the standards), and employing as a means of calibration the age assessments derived from the ammonite faunas, as documented in this Bulletin. As may be seen from the diagram, there is some measure of agree- ment between lithological expression and the postulated eustatic highs and lows. Thus development of coarse- grained sequences (conglomerates, sandstones etc) tends to correspond with falls in sea level, when sea water is SCALE (m) Y1 U LITHOSTRAT. OSEAS "? COLU~~ CORREL. p UPPER TITH,. a 2 PUT1 SILTSTONE W. ' 2 CONGLOM. g a KINOHAKU U SILTSTONE 0 3 3 < - - - - - - - 3 I 2 4 U l' 2 t- TAKATAHI C 0 l ; 5 L 2 KOWHAI $3 POINT SILTSTONE 0 - u - WAIKUTAKUTA SILTST. 3 KIWI SANOST. OHINERURU 5 5 FORMATION 3 5 3 ORAKA S,,,,,\ z ? > 9 RENGARENGA 2 o 3 GROUP g 2 Z (part) C X U 0 LEIOSTRACA ~ - 1 TRACHYOSTRACA Percentage of total ammonite fauna Figure 58 Faunal specha for the Late Jurassic ammonite faunas of New Zealand. The lithostratigraphic column is based on Fleming & Kear (1960) and the overseas correlations are those adopted in the current study (Fig. 54). The eustatic curve is based on tlaq et al. (1988). as modified by Strohmenger et al. (1991). The histograms illustrate the proportions expressed as a percentage of Leiostraca and Trachyostraca in the ammonite faunas oftheNew Zealand Late Jurassic. The occurrences of giant ammonites in the New Zealand sequence are also noted to the far right of the diagram (see p. 107 and Fig. 62). shallower over the continental shelves. Conversely, the example by Strohmenger et al. (1991) and Li & Grant- development of fine-grained sequences generally coincides Mackie (1 993), is reflected by development ofthe Takatahi with periods of rises in sea level, when sea water deep- Conglomerate. Another low in sea level in the later half ened over the continental shelves. ofthe Early Kimmeridgian (Marques et al. 1991) is prob- ably reflected by development ofthe Kiwi Sandstone. The The marked fall in sea level at the boundary between Late extensive siltstone sequences ofthe Puti Siltstone and the Kimmeridgian and Early Tithonian, as documented for Kinohaku Siltstone appear to have developed during Figure 59 Faunal spectra similar to those plotted in Fig. 58 have been published by authors such as Ziegler (1967). Recent examples have been provided by Ceccaet al. (1990. 1993), and the abovediagram is derived from these authors. The histograms show the percentage proportions of Leiostraca and Trachyostraca for the Lower and Middle Tithonian of the Umbria-Marche region of the Apennines of Northern Italy. A eustatic curve derived from Haq et al. (1988) and Strohmenger et al. (1991) has been plotted to the lefl of the figure. (Ph = Phylloceratina: L = Lytoceratina). 2 z 0, W times of high sea level, which were presumably accompa- nied by optimal conditions for the deposition of fme- grained sediments. However, a major exception is the Waiharakeke Conglomerate, which appears to have been deposited at a time when sea levels were probably at their highest during the Jurassic (see Haq et al. 1988). There- fore, although lithology to some degree matches the world- wide sequences of eustatic fluctuations during the Kimmerideian and Tithonian, the presence of mismatches, Urnbria-Marche Apennines (Italy) by Strohmenger et al. (1991); Marques et al. (1991); Li & Grant-Mackie (1993) and Norris & Hallam (1995). None- theless, considering that the New Zealand region in the Late Jurassic was sited close to an active plate margin (Sporli 1987; Sporli & Ballance 1989; Wilson et al. 1989), and was being affected by movements associated with the Rangitata Orogeny, the quality of the overall match with the world-wide eustatic fluctuations is reasonably good. - such as that ofthe Waiharakeke conglomerate, is perhaps The stratigraphic imprint of the eustatic fluctuations ap- evidence for contem~oraneous local tectonic activity pears to continue into the lower part ofthe Upper Tithonian, V) z if the Coleman Conglomerate is interpreted as the record Local tectonic activity, related to the early phases of the of a marked regression, spanning the top of the ponfi zone Rangitata Orogeny (Suggate 1978), was probably respon- and the bottom of the scruposus zone (Haq et al. 1988; sible for local shallowing and the deposition of coarse- grained sediment. The effects of similar local tectonism Strohmenger et al. 1991). Z 5 Z 0 I k L - on the Late Jurassic eustatic record have been documented The overlying formation, the Waikorea Siltstone, repre- z 8 = E F:- 3% 2: 32 0 :: > V] z K5 $6 01 -'k 2 2 ;: +- LEIOSTRACA TRACHYOSTRACA I I I I I l INTER- NATIONAL STAGE Z 5 Z 0 E F K W P P 3 z 5 Z 0 I 2 W -I 0 E 7 LOWEF TITH. z 5 X K W I z X K W P P a Z 5 :: z W I 3 a r S Figure 60 (opposite) In this figure the eustatic curves of Haq et al. 1988 (modified by Strohmenger et al. 1991 and Hallam 1988) have been fined to the New Zealand Late Jurassic stratigraphic column (see Fig. 53). using the correlations derived from the current ammonite study. The litholo~ for the Kawhia column is from Fleming & Kear (1 960). Kear & Fleming (1976), with amendments by Meesook (1989) (see also Ballance & Campbell 1993, fig. 3). The lithology for the Port Waikato column is from Purser (1961) and Waterhouse (1978)). The dominant lithologies that are coarser than clay and silt (i.e. fine, medium, coarse and very coarse sand and gravel) have been highlighted by the dark tone pattern. sents a partial recovery of sea level. However, as indi- cated by Ballance (l988), much ofthe Waikorea Siltstone appears to represent a marginally marine environment, unfavourable to most forms of marine life. A near-shore environment is indicated, with exposure to frequent surges of coarse-grained sediment flows. Although sparse Buchio and belemnites are present, no ammonites have been col- lected to date and they appear to be genuinely absent. The introduction ofthe massive non-marine braidplain fan deposits of the Huriwai Group (Rodgers & Grant-Mackie 1978; Waterhouse 1978; Ballance et al. 1980; Ballance 1988) terminated the Jurassic marine record in New Zea- land and heralded the commencement of the main phase of the Rangitata Orogeny (Suggate 1978) that continued into the Early Cretaceous (Late Aptian) and was responsi- ble for the development of an extensive ancestral land- mass in theNew ZealandiNew Caledonian region (Stevens 1989; Stevens & Fleming 1978). RELATIONSHIF' OF AMMONITE BIOTA TO LATE JURASSIC EUSTASY As noted by Stevens (l990a), biological changes that are likely to accompany rising sea levels include: high diver- sity, increases in speciation rates, influxes of off-shelf and open oceanic faunas, and influxes of taxa with wide-rang- ing geographic distribution (e.g. Cosmopolitan, Tethyan etc.). On the other hand, falling sea levels are accompa- nied by low diversity, extinctions, biostratigraphic gaps, absence or severe restriction of shelf facies, and increases in endemism. Such biological changes can be identified in theNew Zealand Jurassic fossil record (Stevens 1990a). Hantzpergue (1995) and Hoedemaeker (1995) have made similar studies in the European Kimmeridgian and lowest Cretaceous, respectively. Although ammonite assemblages form relatively minor constituents of the total fossil fauna of the New Zealand Late Jurassic, they do nonetheless ex- hibit the main features of the biological changes that are probably related to sea level fluctuations. The eustatic fluctuations ofthe Kimmeridgian are reflected by the tumover and diversity values for the ammonite as- semblages of the Upper Heterian and Lower Ohauan. Thus, the tumover and diversity values for the ammonite assemblages ofthe Ohiiernrn Formation and Waikutakuta Siltstone can be interpreted as a probable response to the rising sea levels of the time. Similarly, the influx of Leiostraca in the Ohinerurn Formation (reaching 56.2% ofthe total ammonite assemblage) is probably a reflection of an influx of offshore/oceanic taxa, moved towards the shore by the rising sea level (Zeiss 1994; Geyssant 1994; Hantzpergue 1995). As already documented by Stevens (1990a) in relation to the total Jurassic fossil fauna, the rise in sea level to reach a major peak in the Middle Tithonian is particularly well marked in biotic patterns. The ammonite assemblages of the Kinohaku Siltstone show the highest values for tumo- ver and diversity, which as also has been demonstrated by Hoedemaeker (1995), may be interpreted as the fauna1 response to a major rise in sea level. However, unlike the assemblages in the Ohine~~ Formation, Trachyostraca are dominant (95.03%) in the Kinohaku Siltstone and Leiostraca constitute only 4.96% of the total ammonite assemblage. The continuing high stand of sea level in the Middle Tithonian is also reflected in the ammonite assemblages of the lower and middle parts of the Puti Siltstone. Values for turnover, diversity and abundance are comparable with those for the Kinohaku. After those for the Kinohaku, these values are the second highest for the New Zealand Late Jurassic. Also, like the assemblages of the Kinohaku, Trachyostraca dominate in those ofthe Puti, and Leiostraca constitute only 10.82% ofthe total. As may be seen from Fig. 61, there is a substantial fall-off in turnover, diversity and abundance in the upper part of the Puti Siltstone (i.e. in horizons above those at Puti Point and Motutara Peninsula in the Kawhia Harbour sequence) and this is undoubtedly a response to the falling sea level of the time. The same trend is even more apparent in the overlying Coleman Conglomerate, which according to the eustaticmodels ofboth Haq et al. (1988) and Hallam (1988, 1992) (see also Strohmenger et al. 1991, fig. 8) coincides with a marked low in sea level. The poorly fossiliferous Waikorea Siltstone represents a minor recovery of sea level that was perhaps insufficient to fully restore open-sea oceanic conditions (as noted by Ballance 1988). GIANT AMMONITES AND EUSTASY The coincidence of occurrences of giant ammonites with times of rising sea levels has been discussed by Stevens (1988). A classic situation is that of the Santoniani Campanian of Westphalia involving the occurrences of giant specimens of Pnrnp~rzosia and Pachydiscus, includ- ing the largest ammonite known to science (Stevens 1988, pp. 144-145). These occurrences are clearly related to the shoreline of the SantonianICampanian marine transgres- sion and it is likely that the conditions associated with the rising sea level (probably resulting in the generation of regions of upwelling and general tumover of the water column) have served to lift on to inshore shelf areas repre- sentative samples of populations that were normally resi- dent in deeper waters some distance offshore. Situations that are able to he interpreted as being comparable to those in Westphalia can also be seen in the Kawhia Harbour se- quence. [...]... from the New Zealand Fossil Record File, administered by the Geological Society ofNew Zealand With the exception of some historical materials, most of the New Zealand collections are located by means of a grid reference obtained from the metric series of the New Zealand Mapping Series 1 5 0 000 NZMS 260 To conserve space, the names of collectors have been abbreviated to initials For a key to the initials,... Zealandjournal ofzoology 16: 699-712 Cooper, R.A 1991: In the Beginning : the earliest history of East Australia andNew Zealand GeoiogicalSocietyofNew Zealand newsletter 92: 47-52 Cooper, R.A.; Tulloch A.J 1992: Early Palaeozoic terranes in New Zealand and their relationship to the Lachlan FoldBelt Tectonophysics 214: 129-144 Cope, J.C.W 1967: The Palaeontology and Stratigraphy of the lower part of the Upper... Malagasy and the Eastern Pacific seaboard (Antarctic Peninsula, South and Cenhal America) Other invertebrate faunas mirror the same affinities (Stevens 1990a; Damborenea & Mancenido 1992) If the postulate is accepted that the Tethyan faunas were generally intolerant of cool or cold temperatures (Stevens 1980a), then the strong possibility exists that they were stenothermal organisms that populated the tropical,... considerably simplifies the links that occurred between New Zealand West Antarctica and South America that have been brought into focus by the present study Also, particularly in the instance ofthe Carey reconstruction, there is amarked simplification in the link that existed betweenNew Zealand and Mexico for a large part of the Late Jurassic (see also Fig 66) Although the absence of Anti-Boreal or Austral... elements may be explained by postulating the presence ofenhanced oceanic circulation in the Southern Hemisphere, as compared with that of northern regions, there still remains the proposition that New Zealand was sited substantially further northwards than depicted in many ofthe conventional continental assemblies An adjunct to this discussion is that most of the palaeoclimatic models (e.g Moore, Hayashidaet... (Lower-MiddleTith0nian)stagein the Port Waikato region of New Zealand Earth science journal 412): 66105 Challinor A.B 1974: Bioshatigraphy ofthe Ohauan and Lower Puaroan stages (middle Kimmeridgian and Lower Tithonian), Port Waikato region, New Zealand, with a description of a new Belemnopsis New Zealand journal of geology and geophysics 17: 235-269 Challinor A.B 1977: Proposal to redefine the Puaroan stage of the New Zealand... Cox, B.M.; Gallois, R.W 1981: The Stratigraphy of the Kimmeridge Clay of the Dorset type area and its correlation with some other Kimmeridgian sequences Institute ofGeological Sciences Report 80/4 Cox, B.M.; Lon, G.K.; Thomas, J.E.; Wilkinson, I P 1987: Upper Jurassic stratigraphy of four shallow cored boreholes in the UK sector ofthe southern North Sea Proceedings of the Yorkshire Geological Society... alteration of some Triassic sediments from Southland, New Zealand Transactions of the Royal Society ofNew Zealand 82: 65-109 Crame, J.A 1981b: The occurrence of Anopaea (Bivalvia : Inoceramidae) in the Antarctic Peninsula Journal of Molluscan Studies 47: 206-219 Coombs D.S 1985: New Zealand Terranes Abstracts Geological Society ofAustralia 14: 45-48 Crame, J.A 1982a: Late Jurassic inoceramid bivalves from the. .. 501), with reference to ammonite biogeography, New Zealand is tectonically complex and composed of a collage oftectonic blocks, some ofwhich probably originated in the equatorial region or in the low latitudes of the Northem Hemisphere (e.g Tozer 1982; Tozer et al 1991) In both New Zealand and Mexico, the occurrences of the ammonite taxa with Mexican -New Zealand affinities are sited on tectonic blocks... Palaeontological Bulletin 21 New Zealand Geological Survey, 3 p Stevens G.R 1965: The Jurassic and Cretaceous Belemnites of New Zealand and a review of the Jurassic and Cretaceous Belemnites of the indo-Pacific Region New ZealondGeological Sunrey paleontological bfrlletin 36 Stevens, G.R 1968: The Jurassic system in New Zealand New Zealand Geological Suwey report 35 Stevens, G.R 1990a: The influences of palaeogeography, . New Zealandjournal ofgeology and geophysics 22 : 26 7 -27 5. Challinor, A.B. 1991: Revision ofthe belemnites ofMisool and a review ofthe belemnites of. Journal of the GeologicalSociety ofLondon 125 : 125 -70. Palaontologie Abhandlunpen 121 : 20 9 -21 8. - Fleming. C.A. 1975: The Geological History of New Zealand