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Volume 47, 1914
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Art. XLV.—The Golden Ridge Graptolites.

Communicated by Professor P. Marshall, M.A., D.Sc., Otago University.

[Read before the Otago Institute, 1st December, 1914.]

[The fossils submitted to Dr. Hall were collected at the Golden Ridge in 1908, and were kept in the School of Mines, Otago University, for four years. From Dr. Hall's report it appears that during this time some of the specimens in different parcels were interchanged. In spite of this misfortune, Dr. Hall's report is of great value, as establishing definitely the relation between the New Zealand graptolites and those of Victoria. It is hoped that further collections will be sent to Dr. Hall shortly.—P. M.]

The graptolites dealt with in the present paper were collected by Professor P. Marshall, Dunedin, some years ago, and I wish to thank him for this opportunity of examining them. The specimens come from three localities—(1) from the tramway half-way between the battery and the Golden Ridge Mine; (2) Butcher's Gully, or Jacob's Ladder, at the head of Malone's Creek; (3) the lowest adit, Golden Ridge Mine.

A map of the district may be found in “New Zealand Geological Survey Bulletin No. 3,” new series, 1907, p. 89. A list of graptolites from Slaty Creek, which bounds the Golden Ridge on the east, is given on pp. 34–37 of the same bulletin.

Dr. Ethel M. R. Shakspear (Miss Woods) in “Geological Magazine,” 1908, pp. 145–48, gives an account of some graptolites from Slaty Creek, near the Aorangi Mine. Owing to differences in the texture of the rock-specimens, this author was enabled to divide the specimens in two series.

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There is a general agreement in the fossils of Dr. Shakspear's collection and the one before me, but owing to an unfortunate accident I have not been able to define the contents of the beds exactly.

None of the specimens were labelled when I received them, but those from each locality were in separate parcels. There was, however, some confusion in the localities. In one instance counterparts were attributed to separate localities, and in two other instances I think that confusion has taken place, though I am unable to distinguish the matrix. The association, however, is not exactly what we know to occur in Victorian strata, unless the two specimens be rejected.

Arranged in descending order, the three localities are placed as follows: (1) Tramway locality; (2) Golden Ridge; (3) Butcher's Gully.

The following species have been identified:—

(1.) From the Tramway Locality.

  • Didymograptus extensus J. Hall.

  • caduceus Salter.

  • bifidus J. Hall.

  • Phyllograptus angustifolius J. Hall (?).

  • Loganograptus logani J. Hall (?).

In Victoria D. bifidus is not associated with the large variety or form of D. caduceus which occurs in these beds. I therefore regard the single specimen of D. bifidus, which has no other fossil on the same slab with it, as wrongly included. There is, so far as I can see, no difference in the matrix, nor, for the matter of that, is there much between that of the three localities. The specimen doubtfully referred to Loganograptus logani is very imperfect, but it is probably that species. Its associates, except D. bifidus, do not forbid it.

(2.) From Lowest Adit of Golden Ridge Mine.

  • Didymograptus mundus T. S. H. var.

  • caduceus Salter.

  • Tetragraptus serra Brong.

  • Dichograptus octobrachiatus J. Hall.

  • Goniograptus cf. crinitus T. S. H.

  • — cf. laxus T. S. H.

  • Phyllograptus angustifolius J. Hall.

  • Diplograptus sp.

The counterpart of the slab that contains D. octobrachiatus and the two species of Goniograptus was included in the collection from the tramway-line, so that their horizon is not quite certain. It is this clear case of confused association that strengthens my idea that two other cases occur as detailed below. D. mundus is closely allied to D. nitidus.

(3.) From Butcher's Gully.

  • Didymograptus extensus J. Hall (probably introduced).

  • caduceus Salter (probably introduced).

  • bifidus J. Hall.

  • Tetragraptus serra Brong. (?)

  • harti T. S. H.

  • pendens Elles.

  • Phyllograptus cf. typus J. Hall.

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The single example of D. caduceus is the large form which in Victoria is not found associated with D. bifidus, but occurs in higher beds. It has, I think, been included by mistake. D. bifidus is very common, and juvenile and well-grown specimens occur. Tetragraptus serra agrees with the figures of the form which J. Hall refers to Brongniart's species, and which has been renamed by Miss Elles and Miss Woods T. amii. T. harti resembles T. quadribrachiatus J. Hall, but has only one theca in the primary branch, and is much more slender. The sicula is well shown in the two examples present. Phyllograptus cf. typus comprises several specimens of lanceolate forms of various sizes.

Age of the Beds.

Judging by the Victorian standards, and eliminating the two specimens that I regard as intruders, the beds may be arranged in the order given above. They represent the middle and lower series of the Castlemainian. The Bendigonian, characterized by Tetragraptus fruticosus, is with us usually only a few feet below the beds corresponding with those of Butcher's Gully, and it would be of interest to see whether this series is not represented in the locality which has yielded the present series of fossils. The presence of Lancefieldian has been proved at Preservation, as shown by a previous paper to the Institute.

For convenience, the Victorian divisions of the Ordovician are here given, especially as a recent work on geology coming from a faulty source gives them wrongly:—

  • Upper Ordovician.

  • Lower Ordovician Darriwillian.

  • Castlemainian.

  • Bendigonian.

  • Lancefieldian.