New Graptolite Localities in the Aorangi Mine Area, North-west Nelson

Transactions of the Royal Society of New Zealand : Geology, Volume 4, Issue 8, 1 September 1966, Page 171

New Graptolite Localities in the Aorangi Mine Area, North-west Nelson

G. J. Smith,

By

Victoria University of Wellington [.Received by the Editor, 15 November 1965.]

Abstract

Graptolites from nine new localities in the Aorangi Mine area are listed. Tetragraptus approximatus Nicholson and Oncograptus upsilon Hall are described in detail, being recorded for the first time from Nelson Province,

Introduction

New graptolite localities were discovered in the Aorangi Mine area during short visits in May and December, 1963. Four localities (S2/541, 542, 543, 544) are in the upper reaches of the Sandhill Creek between and 2 miles south of previously recorded sites (Benson, 1936; Skwarko, 1961), four lie to the northwest of the area mapped by Benson (1936), and one is 8 chains farther up from Benson’s locality H, in Jimmy Creek.

Discussion

The graptolites occur in narrow pyritic slate bands in quartzite. The strata dip steeply and have a north-south regional strike.

A key species in Victoria, Australia, Oncograptus upsilon, which has not been recorded in New Zealand previously, occurs at two of the new localities, S2/540 and 546. This species is restricted to Yapeenian substage 1 (Thomas, 1960), which is thus recognised in New Zealand for the first time.

Tetragraptus approximatus has been described from Cape Providence (Skwarko, 1958) but was not previously known from the Aorangi Mine area. The new localities were found fairly easily, and it is obvious that further graptolite-bearing slates are still to be discovered (Wellman, 1962; Skwarko, 1961). The graptolitic beds at Aorangi Mine are likely to extend southward to the Aorere Valley, where they were discovered by a Victoria University party in 1963 (H. W. Wellman and P. Vella, pers. comm.).

Systematic Descriptions

Class GRAPTOLITHINA

Order GRAPTOLOIDEA

Family DICHOGRAPTIDAE Lapworth, 1873

Section TETRAGRAPTI

Genus Tetragraptus Salter, 1863

Tetragraptus approximates (Nicholson), Fig. 2 (1).

1875. Nicholson, Monograph of British Graptolitidae.

1955. Bulman, Treatise of Invertebrate Paleontology Pt. 5, p. 79, fig. 56, lc.

Sicula not observed. Primary branches arising at 180°; uniformly Imm in width and each 2.5 mm in length, branching by dichotomy at their extremes.

Secondary branches disposed at 180° to each other, 2mm thick and up to 40mm long. Thus the secondary branches are parallel to each other. Thecae 6-7 in 10mm, inclined at 35° to stipe, with an overlap not exceeding two-thirds. Free ventral edge slightly concave, apertural margins concave and normal to the thecal axis. Overall width of rhabdosome 6mm and incomplete length 80mm.

Section DIDYMOGRAPTI

Genus Oncograptus Hall, 1914

Oncograptus upsilon Hall, Fig. 2 (2).

1914. Hall, Proc. roy. Soc. Vict. 27; pp. 104, 118, PI. 17, 18.

1955. Bulman, Treatise of Invertebrate Paleontology, Pt. 5, p. 81, fig. 57, 6.

Sicula barely visible. Rapidly expanding biserial portion widens from an initial width of 3mm in a length of 14mm to a width of 9mm at the level of bifurcation. The uniserial branches diverge at an angle of 40°, have a uniform width of 4.5 mm, and are at least Bmm long. The total incomplete length of the rhabdosome is 22mm. The first thecae diverge downward, and at the level of bifurcation the thecae are curved downwards from an initial angle of 20° to an angle of 80° with the stipe axis. Thecae 10-12 in 10mm, smm long, widening from o.7mm to Imm at the aperture, which is provided with a long denticle.

References

Benson, W. N., Keble, R. A., King, L. G., and McKee, J. T., 1936. The Ordovician Graptolites of North-west Nelson. Trans, roy. Soc. N.Z. 65(4): 357-82.

Skwarko, S. K., 1958. The Lower Ordovician of Gape Providence: a New Graptolite Zone and a New Species of Schizograptus. N.Z. J. Geol. Geophys. 1 : 256-62.

1961. Ordovician Graptolites of North-west Nelson: Recent Discoveries in the Aorangi Mine Area. N.Z. J. Geol. Geophys. 4(1): 98-108.

Thomas, D. E., 1960. The Zonal Distribution of Australian Graptolites. J. Proc. roy. Soc. N.S.W. 94: 1-58.

Wellman, H. W., 1962. New Graptolite Localities in New Zealand. N.Z. J. Geol. Geophys. 5(4): 642-5.

G. J. Smith, B.Sc.(Hons.), Department of Agriculture, Palmerston North, N.Z.

Sheet Fossil Number Victoria University of Wellington Collection Number Grid Reference Description Age (Paleontological Evidence) S2/540 VI043 S2/873981 Five chains upstream from the waterfall in Jimmy Greek, a tributary of Little Slaty Greek. Yapeenian, substage 1 S2/541 VI044 S2/868974 One chain downstream from the large plungepool in Sandhill Creek, half a mile south of the Aorangi Mine. Bendigonian, substage 1 S2/542 VI045 S2/870973 In Sandhill Creek five chains upstream from S2/541. GastlemanianLower Yapeenian S2/543 VI046 S2/878971 Upstream from S2/542 and 7 chains below the junction of the East and West Branches of Sandhill Greek. Upper GastlemanianLower Yapeenian S2/544 VI047 S2/877965 Seven chains upstream from S2/543, 2 chains up the west bank tributary of the West Branch of Sandhill Creek. Upper GastlemanianLower Yapeenian S2/545 VI048 S2/860009 On the south bank of Slaty Creek, 4 chains upstream from the Slaty Creek Battery, which is just upstream from the gravel pit used by the Taitapu Timber Company. Upper Bendigonian S2/546 V1321 S2/868003 On the south wall of Slaty Greek, at the top of the first gorge above Lake Otuhie opposite an old gold battery. GastlemanianLower Yapeenian S2/547 V1322 S2/862016 North-west of Baldy 1,058ft, in the bed of the first west-bank tributary of Slaty Creek upstream from Lake Otuhie. Gastlemanian S2/548 V1323 S2/860009 On the south bank of Slaty Greek opposite the Slaty Greek Battery, upper Sin of the slate band. GastlemanianYapeenian

Table I.—Description of Localities.

x — Common o = Rare V1043 VI044 V1045 VI046 V1047 V1048 V1321 V1322 V1323 Goniograptus thureau (McCoy) o Dichograptus octobrachiatus Hall X Tetragraptus sp. Salter o o o o Tetragraptus approximatus (Nicholson) X Tetragraptus quadribrachiatus (Hall) X Phyllograptus anna (Hall) X X o Didymograptus extensus (Hall) X o o o o Didymograptus v. deflexus (Hall) X X Isograptus caduceus victoriae Harris X X X X X X X X Isograptus caduceus maximus Harris X Isograptus caduceus maximo-divergens Harris o Oncograptus upsilon Hall o o

Table ll.—Distribution of Graptolites.