Introducción

Table 5.3 shows that Nothofagus fusca-type pollen makes up more than 90% of pollen from this unit. Podocarpus and Coprosma spp. are present in small amounts at 2% along with N. menziesii (1%). Griselinia, Halocarpus, Muehlenbeckia, and Leptospermum

Table 5.2a: Radionuclide and water contents

Sample Unit Code Depth below dDc/dt (Gy/ka)¹ Water U (µg/g) U (µg/g)³ U (µg/g) Th (µg/g)³ K%

surface (m) content from ²³⁴Th, from ²²⁶Ra, from ²¹⁰Pb from ²⁰⁸Tl, δ^{2 214}Pb, ²¹⁴Bi ²¹²Pb, ²²⁸Ac

WLL451 KR-B2 3.5 0.1300±0.0065 1.357 5.23±0.33 3.98±0.06 5.29±0.30 14.91±0.17 2.15±0.05 WLL452 KR-A3 4.7 0.1121±0.0056 1.252 6.57±0.46 4.70±0.07 5.49±0.39 16.68±0.21 3.21±0.07

1Contribution of cosmic radiation to the total doserate, calculated as proposed by Prescott & Hutton (Prescott & Hutton, 1994).

2Ratio wet sample to dry sample weight. Errors assumed 50% of (δ-1).

3. U and Th-content is calculated from the error weighted mean of the isotope equivalent contents.

All numbers marked in bold: Minor radioactive disequilibrium (significant on 2σ-level), either between ²³⁴Th and ²²⁶Ra (probably due to Radium migration associated with water flow), or between ²²⁶Ra and ²¹⁰Pb (probably due to influx of Radon).

Table 5.2b: Measured a-value and equivalent dose, doserate and luminescence age

Sample a-value D^e (Gy) dD/dt (Gy/ka) OSL-age (Ka) Unit Code

*WLL451 0.069±0.005 126±3.3 4.46±0.38 28.4±2.9 KR-B2

(4.14±0.38) 30.6±2.9)

*WLL452 0.076±0.008 226±23.5 6.25±0.45 36.2±4.9 KR-A3 (5.90±0.45) (38.4±4.9)

* These samples showed a radioactive disequilibrium (see Table 2b), and the given age was corrected accordingly. As the level of disequilibrium over time is unknown, this age is only a better estimate and cannot be seen as the true age. In brackets the uncorrected doserates and ages are given, calculated under the invalid assumption that the samples were in radioactive equilibrium (²²⁶Ra contents used for calculation)

Table 5.3. Percentage composition of spot pollen samples from the Keoghan’s Road Site. Actual pollen counts are provided in Appendix 4.

Taxon Type KR-A3 KR-B2

Terrestrial Taxa

Nothofagus fusca-type tree 91.1 93.2 Nothofagus menziesii tree 0.8 3.4 Prumnopitys taxifolia tree 0.3

Podocarpus prostrate shrubs/tall trees 1.4 Metrosideros lianes/shrubs/small to tall trees 0.3

Quintinia small tree 0.3 Epiaecridaceae prostrate & erect shrubs 0.3

Genistoma tall shrub 0.3

Gramineae, Epacridaceae and Ascarina. The tree and shrub pollen clearly indicates a closed canopy Fuscaspora beech forest with scattered silver beech (Macphail &

McQueen, 1983). Podocarp pollen occurs in such low amounts that it is probably derived from elsewhere (Macphail & McQueen, 1983). Broadleafs and shrubs are typically under-represented in pollen diagrams and may indicate either long distance dispersal or rare local occurrence. Coprosmas in particular occur in beech forests and are well enough represented to suggest local occurrence (Macphail & McQueen, 1983). The understorey consists of a mix of mono- and trilete ferns and sedges, the relative abundance of

Cyperaceae pollen (5.7%) indicates a moist environment such as would be found on a flood plain.

Palaeoenvironment - beetles

A total of 12 beetle taxa from seven families were collected from the KR-A3 unit. All taxa are associated with forests or are eurytopic (Table 5.4) indicating that the site was forested at the time KR-A3 was deposited. In particular members of the genus Nestrius (weevils, family Curculionidae) are known for being flightless, leaf-litter inhabiting taxa (Kuschel, 1964) indicating the presence of forest litter at the site.

Table 5.4. Taxonomic list of fossil beetle taxa and their associated environments from Keoghan’s Road Sample KR-A3. Fossil parts are given a letter designation e= elytron, p = pronotum and h = head.

Environmental information was collated from ¹Kuschel 1964; ²Emberson & Matthews 1973; ³McColl 1982; ⁴Newton 1984; ⁵Barratt & Patrick 1987; ⁶Booth et al. 1990; ⁷Lyal 1993; ⁸May 1993; ⁹Klimaszewski et al. 1996; ¹⁰Hansen 1997; ¹¹Klimaszewski & Watt 1997; ¹²Marra 2003; ¹³NZAC specimen label information and ¹⁴LUNZ specimen label information

Family taxon Fossil Element Environment Hydrophilidae Tormus c.f. nitidulus Broun e Forest 10, 11, 13

Staphylinidae Paratrochus “sp. group A” e, p Eurytopic 3, 4, 6, 9, 11

Scarabidae Saphobius edwardsi Sharp h Forest 2, 6, 11, 13, 14

Byrrhidae Epichorius “sp. group A” p Eurytopic ^{5, 11, 13} Bothrididae Ascetoderes indet. sp. p Forest ^{11, 13} Zopheridae Pycnomerus marginalis Broun p Forest 11, 13, 14

Pycnomerus rufficolis Broun p Forest ^{11, 13, 14} Pycnomerus “sp. group A” e Forest ^{11, 13, 14} Pycnomerus “sp. group B” e Forest ^{11, 13, 14} Curculionidae Cryptorynchini indet spp. e Forest ^{7, 8, 12}

“Metacalles genus group” sp. h Forest ^{7, 8, 12} Nestrius “sp. group A” e Forest ¹

The Cryptorhynchini species, a tribe of weevils known to be endophytic on dead woody plants, (Lyal, 1993) and the presence of the genus Pycnomerus (family Zopheridae), found predominantly in loose and rotten bark or under litter and stones in

the interpretation of this fauna as representing a forest environment. The presence of the hydrophiliel water beetle (family Hydrophilidae) Tormus nitidulus Broun, a member of subfamily Sphaeridiinae, a group known for their habitation of damp, decaying matter (Booth et al., 1990) indicates that the environment was also moist.

Palaeoclimate

Collection location data, required for the construction of climate envelopes, was available for ten of the twelve taxa identified from this unit. Data was unavailable for the distribution of the unknown Cryptorynchini weevils and the weevils of the “Metacalles genus group”. The results of the climatic reconstructions from these taxa are presented in Fig. 5.3a-b and Fig. 5.4.

Figure 5.3a illustrates a mean summer temperature range of between 15.1ºC and 18.2ºC.

This straddles the modern mean summer temperature at this site (16.5ºC (Leathwick et al., 1998)) giving a median value of 16.7ºC which suggests no discernable change from modern conditions. The winter mean daily minimum temperature reconstruction (Fig.

5.3b) also straddles the modern mean for Keoghan’s Road with a range of -0.3ºC to 4.3ºC, a mean drop of 1.1ºC from the present day mean minimum winter temperature of 3.4ºC (Leathwick et al., 1998). This variance in the difference between modern and reconstructed temperatures during summer and winter may indicate increased seasonality over the present day.

Figure 5.3. Keoghan’s Road (Unit KR-A3) climatic reconstructions: 3a. Mean Summer (February) Temperature Reconstruction; 3b. Keoghan Road (Unit KR-A3) Minimum Winter (July) Temperature Reconstruction. The blue horizontal bars in these figures indicate the range of the variable within which the taxon is known to inhabit. The grey ends of the bars represent the error to these known ranges as calculated by the MLE models. The darker green box indicates the reconstructed range of the variable including the MLE error while the light green box illustrates the reconstructed range without the MLE error term. The solid red vertical line represents the present day mean value of the variable at the site as derived from the climate surfaces of Leathwick et al. (1998). Taxa considered to be outliers are indicated by dashed red circles and are discussed in the text.

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Figure 5.4. Keoghan Road (Unit KR-A3) Mean Annual Precipitation Reconstruction. The blue horizontal bars in these figures indicate the range of mean annual precipitation within which the taxon is known to inhabit. The grey ends of the bars represent the error to these known ranges as calculated by the MLE models. The darker green box indicates the reconstructed ra nge of the variable including the MLE error while the light green box illustrates the reconstructed range without the MLE error term. The solid red vertical line represents the present day mean value of the variable at the site as derived from the climate surfaces of Leathwick et al. (1998). Taxa considered to be outliers are indicated by dashed red circles and are discussed in the text.

Figure 5.4 examines mean annual rainfall from KR-A3 and indicates that in addition to possible seasonal cooling at this time the environment was also drier, with mean annual precipitation (MAP) of between 1,460mm and 2,250mm per year. This is a reduction of 461mm to 1251mm from the current mean of 2,711mm per year (Leathwick et al., 1998), or a reduction in MAP of between 17-46% lower than present day.

5.3.4 Palaeoenvironment and palaeoclimate of unit KR-B2