ARCHAEOLOGICAL SITES AND OBSIDIAN DEPOSITS ON THE MOKOHINAU ISLANDS, HAURAKI GULF

by P.R. Moore 217 Riverside Drive, Lower Hutt.

S U M M A R Y

Thirteen archaeological sites were recorded on the Mokohinau Islands in addition to the nine previously reported by Spring-Rice (1980) on Fanal Island. This includes at least one pa, terraces, midden, find spots, as well as several areas of broken obsidian (flakes and pieces), shell, and cooking stones related to mutton-birding activities. Parts of Burgess Island and the Knights Group were probably cultivated.

Natural obsidian deposits on Fanal Island were exploited by mutton-birding parties, and also by the occupants of Burgess Island and the Knights Group. The nature of the deposits, and physical characteristics of the obsidian, are described.

Archaeological evidence suggests the Mokohinau Islands were prob­ably occupied by a small permanent population for only a short period of time, perhaps less than 100 years.

INTRODUCTION

The Mokohinau Islands are the most isolated of the island groups in the Hauraki Gulf, lying 100 km N N E of Auckland and 25 km northwest of Great Barrier Island (Fig.l). The group consists of two main islands — Fanal (73 ha) and Burgess (52 ha) — as well as a cluster of smaller islands and stacks adjacent to Burgess Island known as the Knights Group. A general description of the Mokohinau islands is provided by Wright (1980).

According to Sandager (1889, p.292) a hapu of Gt Barrier Maoris "occupied at no very remote time the Mokohinou (sic) Islands per­manently, many of them being buried in part of the boulder beach which is still considered tapu". This obviously refers to Burgess Is (Pokohinu), but since the erection of a lighthouse in 1883 the island has been considerably modified and very little evidence of former Maori occupa­tion remains.

In comparison, Fanal Island has remained largely unmodified in the past 100 years. Nine archaeological sites were recorded by Spring-Rice (1980), including terraces, a pit, and areas of broken obsidian (Fig. 2). Natural obsidian deposits on the island (see Browne & Greig 1980) provided visiting mutton-birding parties with a ready source of sharp flakes for butchering of the juvenile grey-faced petrel, or "ooi" as they

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Fig.l. Location map, and position of archaeological sites on Burgess Island and the Knights Group.

were known (Sandager 1889)1. Mutton-birders apparently continued to exploit the seabird population on Fanal Is. on a regular basis up until about 25 years ago (Wright 1980).

A n archaeological survey of the Mokohinau islands was undertaken over a seven-day period in December 1983-January 1984 as part of a scientific expedition organised by the Offshore Islands Research Group. Most of the time was spent on Burgess Island and the Knights Group, but a one-day visit was also made to Fanal.

A N N O T A T E D LIST OF SITES

Grid references refer to the metric (NZMS 260) sheet S07, and were obtained from an unpublished 1:10 000 scale topoplot: 1 In December 1888, 3000 birds were taken off Fanal and Burgess islands.

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04 OS I i

Fig. 2. Location of archaeological sites, mutton-birding areas and obsidian deposits on Fanal Island. Sites recorded in May 1979 are described by Spring-Rice (1980). Fanal Island lies 4 km SE of Burgess Island.

Site No.

1. (0117 8592). Find spot. Two obsidian flakes (Z3735/l,2) at top of cliff above wharf, Landing Bay, Burgess Island.

2. (0068 8560). Midden/terraces. East side of Hokoromea, on small point. Three obsidian flakes (Z3736), dark charcoal-rich soil, associated with several natural terraces. Concentration of Nerita shells c.40 m inland.

3. (0067 8550). Find spot. Southeast end of Hokoromea, on small island joined to main island at low tide. Single obsidian flake (Z3737).

4. (0050 8565). Pa. Headland forming north end of Hokoromea. Series of terraces on higher slopes; ditch at narrowest point c. 2 m wide x 6 m long.

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5. (9995 8550). Pa? Northwest end of Trig Island (Atihau). No terracing or midden seen, but appears to be ditch c. 10 m long x 1.5 m wide cutting off headland.

6. (0006 8524). Midden. Near middle of Trig Island (Atihau). Minor shell, 3 tiny obsidian flakes, rounded pebbles. One obsidian flake collected about 40 m to the south.

7. (0492 8194) Mutton-birding area? East end of Fanal Island, at top of cliff. Scatter of obsidian.

8. (0480 8195) Occupation/working area. East end of Fanal Island; large flat area on high point. High concentration of obsidian, minor shell, on SE side of flat area, covering minimum 20 m x 10 m. Well-rounded cobbles, minor obsidian on flat area.

9. (0447 8213). Mutton-birding area. ('Pahuhunui'). Middle of Fanal Island, on gentle SW-slope, north side of "Eastern Valley". Scatter of obsidian, charcoal, shell over area of at least 50 m x 20 m.

10. (0438 8234). Mutton-birding area? ('Haukawakawa'). Northern part of Fanal Island, on ridge crest near high point (127 m). Few shell fragments, single obsidian core.

11. (0435 8250).Mutton-birding area ('Harakekeroa'). Northern Fan­al island, on ridge crest near head of "Northern Valley". Scattered obsidian.

12. (0410 8234). Midden. Northern Fanal Island, on ridge crest between "Northern" and "Central" valleys. Obsidian boulders, pipi shell, charcoal, fish bone.

13. (0398 8234). Midden/terrace? Northern Fanal Island; prominent flat area on spur west of site 12. Abundant obsidian, charcoal, two Mytilus shells.

DESCRIPTION OF SITE T Y P E S

P a

Headlands at the northern end of Hokoromea and Atihau would have been considered favourable locations for the siting of a pa. Each is surrounded by near-vertical, 30-40 m high, cliffs on three sides, and connected by a narrow neck of land to the remainder of the island.

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The pa on Hokoromea (site 4) was defended by a ditch constructed across the narrowest point, which has a steep, natural scarp on its northern side. A series of terraces on higher slopes of the headland were undoubtedly man-made, and although no shell midden or artefacts were found, the pa may have been occupied for at least a short period of time.

Evidence for a pa at the northern end of Atihau is less certain. There appears to be a shallow ditch on the south side, but no terracing or midden was seen on the headland itself. However, much of the area is presently covered in low scrub, and such features could have been obscured.

The main hill on Burgess Island does not seem to have been a pa, although the upper slopes were substantially modified during construc­tion of the lighthouse and associated facilities, and any prehistoric earthworks could have been destroyed. No pa site was identified on Fanal Island.

Midden

Very little shell midden was found on the islands (none was seen on Burgess), and much of it may have been eliminated through the acid action of leaf litter, fires, and natural erosion. Burgess Island is known to have been fired at frequent intervals from the early 1920's, and vegetation on the Knights Group was probably also burnt off at various times (Wright 1980). The presence of goats, sheep, and cattle almost certainly resulted in the destruction of some sites on Burgess Island.

The relatively common midden on Fanal Island is probably a reflection of minimal European interference with the environment in historic times, and frequent visits by mutton-birding parties. Shellfish species recorded include Cookia sulcata, Nerita melanotragus, Haliotis iris (paua), Thais orbita, Haustrum haustorium, Lunella smaragda, Perna canaliculus (mussel), and Paphies australe (pipi); Spring-Rice (1980) also noted the presence of Cellana sp. Fish bone was found at several sites. With the exception of pipi, and possibly Perna, all of these species could have been obtained on the island itself.

Well-rounded cobbles (up to 30 cm diameter) associated with shell midden at various sites on Fanal Island, and also on the Knights Group, are inferred to be hangi stones. Of two cobbles collected on Fanal, one is probably an andesite and the other appears to be a rhyolite or dacite. Andesite does not occur naturally on the island (Browne & Greig 1980), and the hangi stones were most likely obtained from Burgess Island or the Knights Group.

Mutton-birding areas

Spring-Rice (1980) showed the location of six ancient mutton-birding

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areas on her map of Fanal Island, and in January 1984 obsidian flakes and pieces, as well as minor shell midden, were found at or in close proximity to three of these (Pahuhunui, Haukawakawa, and Harakekeroa). No terracing was seen at these sites, but Spring-Rice recorded a series of five terraces near Arawii, at the eastern end of the island (Fig. 2). Other sites on the island with scattered obsidian and shell midden, particularly those lacking associated terraces (e.g. site 12), could also represent former birding areas. The abundance of obsidian flakes and pieces and well- rounded cobbles (hangi stones?) at site 8 suggests this may have been an important area for the preparation and cooking of mutton birds.

No mutton-birding areas have been identified on other islands in the Mokohinau group, although obsidian flakes (and shell midden) found at site 6 on Atihau, and two sites (2, 3) on Hokoromea could be related to birding activities.

Agricultural areas

Judging from the presence of rounded pebbles in dark top soil covering the topographically-subdued southwestern part of Burgess Island, much of this area was probably cultivated in prehistoric times (Fig. 1). Water would have been available year-round from a natural spring on the western slopes of Lighthouse Hil l .

The central part of Hokoromea may also have been cultivated, considering the large number of well-rounded pebbles found there. It is possible that much of the relatively flat, central part of Atihau was cultivated too. However, the lack of water would have virtually restricted the growing of crops to winter months. No evidence of cultivation has been found on Fanal Island, although Spring-Rice (1980) recorded a single raised-rim pit which could have been used for storing kumara, and it is possible that a large (100 x 30 m) terrace situated nearby was cultivated.

OBSIDIAN

Nature of deposits

The existence of obsidian on Fanal Island was first reported by Fleming (1950), and Browne & Greig (1980) described an agglomerate composed of obsidian blocks up to 40 cm diameter forming a "discon­tinuous carapace over much of the island". A type section for their Agglomerate Member (of Fanal Formation) was designated at a bluff on the south side of the highest point (Mataa, SO7/0435 8265) (Fig 3.)

Re-examination of the type locality revealed a minimum of 8-10 m of

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Fig.3. Bluff on south side of Mataa, Fanal Island, type locality of Browne & Greig's (1980) Agglomerate Member. Weathered rhyolite in the upper part of bluff contains large obsidian "blocks".

highly weathered, crudely flow-banded rhyolite with numerous blocks of obsidian conformably overlying flow-banded rhyolite (Fig. 4). Flow-banding in the upper unit dips about 70° north. The underlying rhyolite is flow-folded, but layering locally also dips 70°N. The obsidian blocks are up to 50 cm diameter (but mostly 10-20 cm), and flow-banding in the obsidian is sub-parallel to that of the enclosing rhyolite (see also Browne & Greig, fig. 2). Hence the "agglomerate" does not represent an air-fall deposit, but probably a partially autobrecciated glassy rhyolite flow. The presence of abundant obsidian blocks up to 80 cm diameter around the northern side of Mataa indicates that the obsidian unit dips slightly northward overall, and is about 20 m thick.

Large obsidian boulders up to 50 cm diameter are also found at various other places (Fig. 2), which suggests that the obsidian unit was formerly distributed over much of Fanal Island. Although it is remotely possible that some large blocks were carried from the north end of the island to be worked elsewhere, the abundance and large size of boulders at several localities suggests this is unlikely. Only a few of the many large boulders on the slopes above the eastern landing show any sign of being worked. Boulders near site 10, and most of those at site 12, also show little or no sign of having been worked. A l l of these occurrences, therefore, are regarded as natural deposits.

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Fig.4. Closer view of bluff showing irregular obsidian "blocks" (dark patches) in weathered, flow-banded rhyolite. Flow-banding in the obsidian is sub-parallel to that of the surrounding rhyolite.

No natural obsidian deposits were found on the other islands, although some perlite and glassy rhyolite outcrops along the southeast­ern cliffs of Burgess.

Physical characteristics

Fleming (1950, p. 267) described the Fanal Island obsidian as "greenish black, slightly amygdaloidal, more opaque and less homogeneous than Mayor Island obsidian, lacking perfect conchoidal fracture". A l l of the obsidian seen by the writer is black, although on surfaces parallel to the flow-banding it may appear medium to dark grey in colour (Rock-colour chart). The obsidian is grey in transmitted light.

Most of the obsidian is weakly to strongly flow-banded, and material from Mataa may be more strongly flow-banded than that from other localities. The obsidian contains abundant, small (0.5-2 mm) crystal inclusions composed of quartz and/or feldspar, but no spherulites.

Although the Fanal Island obsidian is dense and glassy it has an imperfect conchoidal fracture, and produces few well-formed flakes.

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Nevertheless, many flakes and pieces have sufficiently sharp edges for cutting and scraping purposes, as attested by the high percentage of used flakes at site 8.

Obsidian artefacts

A l l except one of the obsidian flakes and pieces found on Burgess Island and the Knights Group were clearly derived from the deposits on Fanal Island. One flake (Z3735/1) from site 1 on Burgess Island evidently had a different source. It is semi-translucent (smoky grey in transmitted light), very vitreous, has a perfect conchoidal fracture, and lacks crystal inclusions. A remnant of pitted cortex on one side indicates that it was struck off a pebble from a colluvial, rather than an alluvial or beach deposit. Overall, the obsidian is similar to that described by Atwell (1973) from Whangaparapara, on Gt Barrier Island, and probably came from a Gt Barrier source.

A l l of the flakes collected from the Knights Group and Burgess Island, with the exception of Z3737 show some sign of edge-wear, which suggests they were probably used for cutting and/or scraping purposes. The one "foreign" flake (Z3735/1) also shows considerable evidence of use. Of the 8 flakes collected from site 8 on Fanal Island 5 showed definite edge wear. Used flakes were also reported by Spring-Rice (1980) from Arawii.

Obsidian cores were found at sites 9 and 10 on Fanal Island.

DISCUSSION

Exactly when, and for how long, the Mokohinau Islands (at least Burgess Island) were occupied by Great Barrier Maoris is unknown, but the archaeological evidence suggests the islands were home to a relatively small group (<100?) for only a short period of time, perhaps 50-100 years. The lack of terracing, storage pits, and midden on Burgess Island is particularly notable, although it is possible some features (especially midden) were destroyed during European occupation (1883-1980). The pa on Hokoromea is the only obviously fortified site, and may have been occupied for a short time. A token effort was apparently also made to strengthen the natural defences of the northern headland of Atihau, but there is no evidence it was ever used as a pa. In view of the limited fortifications there was either a small population living on Burgess Island and the Knights Group, or no significant threat to the local inhabitants.

Archaeological sites on Fanal Island seem to be almost exclusively related to mutton-birding activities, including the manufacture of obsidian flakes for butchering purposes. It is unlikely there was any

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permanent occupation because of the very limited water supply particularly during summer months (Wright 1980). Although some kumara may have been grown and stored for use by parties stranded during stormy weather, visiting groups (presumably from Great Barrier brought a small supply of food (pipi, mussel?) with them to supplement whatever was available locally. The presence of terraces on various parts of the island suggests that temporary shelters were built to accommo­date those involved in mutton-birding, and possibly also for storage.

Fanal Island was undoubtedly also visited by the Maoris living on Burgess Island and the Knights Group, both for mutton birds and to obtain obsidian. Andesite hangi stones found on Fanal must have been transported from Burgess during such visits. These people could also have made occasional voyages to Great Barrier to obtain various items not available on the Mokohinaus.

A C K N O W L E D G E M E N T S

I thank Roger Grace for assistance in the field, and Nigel Prickett for reviewing the paper. Typed by Pearl Matthews.

R E F E R E N C E S

Atwell, E.G. 1973: Archaeological sites, Great Barrier Island. Tane 19: 157-165. Browne, G.H. & Greig, D.A. 1980: Geology of Fanal Island (Motukino), outer Hauraki

Gulf, North Auckland. Tane 26: 7-19. Fleming, C.A. 1950: The geology of the Mokohinau Islands, North Auckland. Part 1 —

general geology. Transactions of the Royal Society of New Zealand 78 (2-3): 255-268. Sandager, F. 1889: Observations on the Mokohinau Islands and the birds which visit them.

Transactions of the New Zealand Institute 22: 286-294. Spring-Rice, W. 1980: Fanal Island (Motukino) archaeological survey and historical

account. Tane 26: 99-105. Wright, A . E . 1980: Auckland University Field Club scientific trip to the Mokohinau

Islands, May 1979. Introduction and Acknowledgements. Tane 26: 1-6.

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