¹⁴C Calibration in the Southern Hemisphere and the Date of the Last Taupo Eruption: Evidence from Tree-Ring Sequences

Abstract

Tree rings from a section of Prumnopitys taxifolia (matai) covering the period AD 1335-1745 have been radiocarbon dated and used to generate a 14C calibration curve for southern hemisphere wood. Comparison of this curve with calibration data for northern hemisphere wood does not show a systematic difference between 14C ages measured in the northern and southern hemispheres. A floating chronology covering 270 yr and terminating at the last Taupo (New Zealand) eruption, derived from a sequence of 10-yr samples of tree rings from Phyllocladus trichomanoides (celery pine, or tanekaha), is also consistent with the absence of a systematic north-south difference, and together with the matai data, fixes the date of the Taupo eruption at AD 232 ± 15.

Reliable14C AMS dates on bird and Pacific ratRattus exulansbone gelatin, from a CaCO3‐rich deposit

“…Although the 14 C age for NZA7532 is less than the accepted mean age for the tephra of 1850 ± 10 years B.P. (Healy 1964;Froggatt 1981;Froggatt & Lowe 1990;Wilson 1993), its calibrated age (AD 247-418, Table 1) was consistent with the date extrapolated from a floating treerm8 chronology (Sparks et al 1995). The calibrated age for NZA8226 was entirely consistent with the range of published ages for the tephra.…”

“…As might be expected for an air fall deposit, the Waimihia Tephra lensed out about 3 m into the shelter, and nowhere was as thick as the overlying ignimbrite. The Waimihia Lapilli is pale grey where unweathered, towards the back of the shelter, and pale yellow to orange-red where weathered beneath soils outside the shelters The Waimihia Tephra was identified by its stratigraphic position (150-400 mm below the Taupo Tephra), thickness (typically 125-150 mm), loose texture, and characteristic orange-red colour on exposure It lensed out within the shelter, and was difficult to discern in the section more than 3 m from the entrance Its texture was loose enough that the lapilli spilled from sections, leaving an indentation between the more coherent sediments below and above Both tephras were erupted from a vent or vents in the eastern part of Lake Taupo (Wilson 1993) The ages of each are constrained by multiple dates on a range of materials (Froggatt & Lowe 1990, Wilson 1993) and for the lgnimbnte by a floating tree-ring chronology (Wilson 1993, Sparks et al 1995 Froggatt & Lowe (1990) gave an average radiocarbon age of 1850 ± 10 years B P for the Taupo Tephra, based on 41 dates on wood, charcoal, and peat from above, beneath, and withm the lgnimbnte and air fall layers (Froggatt 1981) Wilson (1993) and Sparks et al (1995) presented evidence from floating tree-ring chronologies to suggest a calendar date of c AD 186 (Wilson 1993) and AD 232 (Sparks et al 1995) The age of the Waimihia tephra was given by Froggatt & Lowe (1990) as 3280 ± 20 years B P , the average of 17 dates on charcoal and wood Wilson (1993) presented two new dates (Wkl840, 1841) and suggested a 14 C date of 3300 years (3550 calibrated years B P ) For most of the area of its area, the present base of the excavation coincides with the contact of the Waimihia Tephra with the pre-Waimihia cave sediments Within the shelter, the surface of the Taupo lgnimbnte was gullied before cave sedimentation resumed, presumably as a result of exposure to rainfall in the period between destruction of the surrounding forest by the lgmmbrite and the re-establishment oftall vegetation Near the entrance, the lgnimbnte was richer in charcoal than it was farther back, and remnants of a tree branch were traced for over 1 m The thickness of the Y7 subunit was greatest towards the back of the shelter and along the eastern wall, but at no point was it less than 350 mm Above Unit Y, there are three layers of non-volcanic sediment The surface layer ( 1 ) is composed of limestone sand liberally mixed with organic residues including faeces of sheep and rabbits It formed a solid skin over the pre-European sediment layers The abundant bones of introduced mammals indicate that this layer has formed in the past 150 years Layer 1 contained Taupo tephra, derived from rabbit burrows that penetrated the surface layers towards the rear of the shelter Beneath Layer 1, Layer 2 was undisturbed limestone sediment, with an orange tinge Layer 2 was uneven in thickness a...…”

“…Confidence limits for Waimihia Tephra are based on calibration of mean conventional age. Age for Taupo Tephra (upper dashed line) is from Sparks et al (1995). HPE/4 is not shown because it was in mixed post-European surficial sediment.…”

High-Precision Radiocarbon Measurements of Contemporaneous Tree-Ring Dated Wood from the British Isles and New Zealand: Ad 1850–950

“…The cedar trees grew in 2 sites in the middle of the North Island of New Zealand (rings AD 1401-1720, Takapari Forest Park, 40°04′S, 175°59′E; rings AD 1721-1850, Hihitahi Forest Park, 39°32′S, 175°44′E), while the silver pines grew on the west coast of the South Island (Oroko Swamp, 43°14′S, 170°17′E). Knox and McFadgen (2001) claim there is a statistical difference between the North Island cedar data given in McCormac et al (1998a) and the South Island matai data given in Sparks et al (1995) and, furthermore, suggest that the differences might be the result of either geographic location or proximity to the intermittently active volcano, Ruapehu. We consider it unlikely that volcanic emissions have affected the 14 C content of the cedar wood (Rubin et al 1987;Bruns et al 1980), as Hihitahi Forest Park is 32 km away, and Takapari Forest Park is 94 km away from the volcano.…”

A spatio‐temporal model for the invasion of the New Zealand archipelago by the Pacific ratRattus exulans

“…The oldest dates for both main islands cluster at or before the time of emplacement of the Taupo Tephra, the date of which has recently been revised to about AD 232 (Sparks et al 1995). At that time, the forest at Pureora (northwest of Lake Taupo) which was destroyed by the ignimbrite phase of the eruption still supported a fauna of large ground beetles (Kuschel 1987), and the Flc deposit at Waitomo Caves also contained a fauna of large insects (Worthy 1984).…”