Elizabeth M. Kennedy

Quantitative palaeoclimate estimates from Late Cretaceous and Paleocene leaf floras in the northwest of the South Island, New Zealand

Three new plant macrofossil assemblages were collected from Late Cretaceous and Paleocene fluvio-lacustrine sediments of the Pakawau and Kapuni groups in the northwest of the South Island, New Zealand. Palaeoenvironmental interpretations were made from each locality and palaeoclimate was deduced from the dicotyledonous angiosperm leaf component of each flora. A latest Cretaceous (Pakawau Bush Road locality) flora yielded 58 different dicotyledonous leaf forms; the two Paleocene collections, Ians Tip and Pillar Point Track, included 23 and 28 dicotyledonous leaf forms respectively. Quantitative palaeoclimate estimates were obtained using both Leaf Margin Analysis (LMA) and the Climate Leaf Analysis Multivariate Program (CLAMP). Temperature estimates suggest that there was a slight cooling from the latest Cretaceous into the early Paleocene in the northwest Nelson region of New Zealand, supporting similar Southern Hemisphere palaeoclimate findings from Antarctic data. Consistency in temperature estimates using different methods, including LMA, multivariate leaf morphological analysis (CLAMP), oxygen isotope data, regional versus local studies and global palaeoclimate models, suggests that the mean annual temperature for the Pakawau region in the latest Cretaceous was between 12 and 15°C. LMA produced temperature estimates between 6.5 and 8°C for the two Paleocene assemblages whereas CLAMP-produced estimates were slightly higher between 9 and 12.5°C

Paleoclimatic significance of Mid-Cretaceous floras from the middle Clarence Valley, New Zealand

Evidence from leaf-margin analysis and vegetational physiognomy indicates that a mid-Cretaceous flora from the South Island of New Zealand grew at a mean annual temperature of 10 degrees C. This compares with an identical estimate derived from a coeval flora in northern Alaska. Both floras grew at about the same latitude and in coastal plain settings. This study provides the first direct comparison of non-marine near-polar climates in the pre-Tertiary record.

The Sensitivity of CLAMP to Taphonomic Loss of Foliar Physiognomic Characters

Abstract CLAMP (Climate Leaf Analysis Multivariate Program) is a powerful paleoclimate proxy with the ability to yield quantitative data on past temperatures, precipitation, growing season length, and humidity, as well as enthalpy (a property of a parcel of air that is useful in studies of paleoaltimetry). Commonly quoted uncertainties in CLAMP predictions relate to the statistical uncertainty inherent in the combined quality of the modern calibration data sets and the relationship of foliar architecture to the various climate parameters. This minimum uncertainty assumes that the fossil assemblage represents faithfully the foliar physiognomy of the source vegetation. Taphonomic processes degrade this physiognomic fidelity. Differential selection for size, shape, and species composition during transport and post-depositional processes biases the physiognomic profile of the fossil assemblage. The sensitivity of CLAMP precision to taphonomic filtering was assessed empirically using a modern data set from the Crimean Peninsula as a proxy fossil site. Elimination of leaf margin, apex, base, size, and shape character-state categories, singly and in combination, changed the predictive capability of CLAMP. Loss of margin characters had the greatest effect, particularly on temperature-related variables (mean annual, warm-month mean and cold-month mean temperatures, length of the growing season, and enthalpy). Taphonomic selection against large leaf sizes had little effect even on moisture-related estimates (precipitation during the growing season, mean monthly growing season precipitation, precipitation during the three wettest and driest months, relative humidity). Loss of taphonomically sensitive characters (apex, base, or shape) also had little effect on CLAMP predictions.

Foliar Physiognomic Record of Climatic Conditions during Dormancy: Climate Leaf Analysis Multivariate Program (CLAMP) and the Cold Month Mean Temperature

The extent to which the leaves of woody dicots encode in their physiognomy the climatic conditions that exist during dormancy was tested by sampling 20 sites along an approximately west‐east transect across European Russia, the Crimean Peninsula, Western Siberia, and central Eastern Siberia. This transect encompassed the most extreme mean annual temperature range recorded in the modern world where vegetation exists. Climate Leaf Analysis Multivariate Program (CLAMP) revealed little change in calibration of the warm month mean temperature compared with the PHYSG3AR data set derived from less extreme sites primarily in North America and Japan, but significant change with respect to the cold month mean temperature (CMMT) calibration. Although CLAMP underestimated the CMMT by up to 9°C in the coldest sites, the addition of the transect sites improved CLAMP’s performance at low temperatures. This suggests that winter cold is encoded in foliar physiognomy even though the leaves are functional only during the late spring and summer months. This increase in performance was, however, at the cost of decreasing precision. Precipitation predictive capabilities were only slightly affected, but calibration of key climatic variables such as enthalpy, used in determining palaeoaltitude, remained more or less unchanged after the inclusion of the cold transect samples.

Late Cretaceous and Paleocene terrestrial climates of New Zealand: Leaf fossil evidence from South Island assemblages

Abstract Univariate and multivariate leaf morphology‐based analysis of leaf fossil assemblages from localities in the South Island of New Zealand provide quantitative paleoclimate estimates for the terrestrial Late Cretaceous and Paleocene. Favourable growing conditions with a cool to mild temperate climate are inferred for the youngest pollen zone in the Late Cretaceous (PM2) with moderately high precipitation and high dicotyledonous angiosperm diversity. Mean annual temperature estimates of c. 12–16 and c. 7–11°C were produced from northwest Nelson and North Otago PM2 Zone assemblages, respectively. These different temperature estimates most likely reflect differences in age, although geographic differences may also be a factor. Consistent data from three Paleocene assemblages suggest cool‐temperate conditions. Mean annual temperature estimates of c. 6–12°C were produced from these Paleocene assemblages. They also had lower dicotyledonous leaf diversity than the Late Cretaceous assemblages, no more than 30 different angiosperm leaf forms.

Early Paleogene evolution of terrestrial climate in the SW Pacific, Southern New Zealand

[1] We present a long-term record of terrestrial climate change for the Early Paleogene of the Southern Hemisphere that complements previously reported marine temperature records. Using the MBT′-CBT proxy, based on the distribution of soil bacterial glycerol dialkyl glycerol tetraether lipids, we reconstructed mean annual air temperature (MAT) from the Middle Paleocene to Middle Eocene (62–42 Ma) for southern New Zealand. This record is consistent with temperature estimates derived from leaf fossils and palynology, as well as previously published MBT′-CBT records, which provides confidence in absolute temperature estimates. Our record indicates that through this interval, temperatures were typically 5°C warmer than those of today at such latitudes, with more pronounced warming during the Early Eocene Climate Optimum (EECO; ∼50 Ma) when MAT was ∼20°C. Moreover, the EECO MATs are similar to those determined for Antarctica, with a weak high-latitude terrestrial temperature gradient (∼5°C) developing by the Middle Eocene. We also document a short-lived cooling episode in the early Late Paleocene when MAT was comparable to present. This record corroborates the trends documented by sea surface temperature (SST) proxies, although absolute SSTs are up to 6°C warmer than MATs. Although the high-calibration error of the MBT′-CBT proxy dictates caution, the good match between our MAT results and modeled temperatures supports the suggestion that SST records suffer from a warm (summer?) bias, particularly during times of peak warming.

Probable Gobiomorphus fossils from the Miocene and Pleistocene of New Zealand (Teleostei: Eleotridae)

Abstract Fish fossils that appear to be of Gobiomorphus species are described from lake sediments from widely separated localities: near St Bathans, Central Otago, and the Ormond Valley of the Waipaoa River, inland from Gisborne. Dating of the sites suggests that the fishes from Central Otago are Early Miocene in age (c. 20–16 million years old), while those from Ormond Valley are of mid‐Pleistocene age (c. 620 000 years).

Oligocene paleogeography of New Zealand: maximum marine transgression

This Special Issue of the New Zealand Journal of Geology and Geophysics is part of the on-going debate as to whether all of the continent of Zealandia was completely below sea level sometime during...

A fossil southern grayling, genus Prototroctes, from the Pleistocene of north‐eastern New Zealand (Teleostei: Retropinnidae)

Abstract This paper reports two fossil fishes, most probably of the genus Prototroctes, from a mid‐Pleistocene lake deposit in north‐eastern New Zealand. These are the first known fossils of this genus, which is found only in south‐eastern Australia and New Zealand.

An outcrop‐based study of the economically significant Late Cretaceous Rakopi Formation, northwest Nelson, Taranaki Basin, New Zealand

Abstract The Late Cretaceous Rakopi Formation (Pakawau Group) represents one of the most important petroleum source rock units and a potential reservoir unit in the highly prospective Taranaki Basin. This paper presents a predominantly outcrop‐based study of the sedimentology, petrography, stratigraphy, and depositional environment of the Rakopi Formation in the Paturau River and Pakawau areas of northwest Nelson, southern Taranaki Basin, together with some preliminary insights into the stratigraphie architecture of the Pakawau Group on a more basin‐wide scale. The Rakopi Formation is interpreted here as a terrestrial deposit, representing sedimentation in fluvial channels and their associated overbank and levee environments. However, the presence of dinoflagellates, glauconite, and elevated coal seam sulfur contents is evidence for periodic marine influence during deposition. This could be explained by a low‐gradient coastal plain paleogeography, crossed by a series of rivers and their associated floodplain deposits, episodically inundated by marine incursions during successive transgressions. A modern analogue setting from the present‐day Hauraki Graben, North Island, New Zealand, indicates that marine influence within coastal plain systems can extend several tens of kilometres inland. Given such a physiography, relatively small increases in relative sea level could potentially move the shoreline several kilometres or tens of kilometres farther inland, sufficient to introduce the type of marine influence on sedimentation that we suggest for the Rakopi Formation. The results from this study suggest a greater marine influence within the Rakopi Formation, northward into the greater Taranaki Basin, than has previously been recognised. This raises the possibility of both different reservoir facies as well as potentially a greater proportion of marine mudstones, which would have implications for both reservoir and trapping of hydrocarbons. In addition, marine‐influenced coaly rocks within the Rakopi Formation are expected to have greater petroleum generative potentials and to be more oil‐prone than their fully non‐marine counterparts.