by Neil Phillips FAusIMM(CP) and John Clemens
Many geological field guides are either hastily assembled extracts from published journal articles or densely written volumes for geologists with a very specific professional expertise. The guide recently produced for the Granites2017@Benalla Symposium, published by Outdoor Recreation in Australia, Geology of the Tallarook Plateau by Neil Phillips and John Clemens – is a refreshing exception.
Printed on high quality paper in a clear sans serif font, beautifully formatted and illustrated by numerous colour photographs and uncluttered maps and diagrams, this conveniently-sized (A5) 58-page booklet is an excellent introduction to Tallarook Plateau geology for geologists and non-geologists alike.
The volume opens with a short introduction to the location and geography of the plateau, followed by a paragraph on, and illustration of, each of the major rock types to be found in the region. Next comes a geological history of the Devonian (~366 Ma) Tallarook Granite, the major geological feature of the plateau, and a discussion of the mineralogy of the granite, culminating in a section on the mineral that makes the granite special – cordierite. These sections of the guide are carefully structured, and the language and terminology employed are consciously designed in a way that will not exclude those who do not have geological training.
On the other hand, the authors in no way talk down to their readers, and there will be many a geologist, and particularly geology student, who finds themselves learning new things, particularly about cordierite, its occurrence, petrogenesis and significance. For some, the most useful practical items will be the descriptions of the various ways that cordierite appears in granite and the field photo of cordierite in situ. For the geochemists, there is a table of the major and trace element compositions of the three main granite types, along with their O, Sr and Nd isotopic compositions.
The main part of the guide is a series of 15 stops designed to introduce the field-tripper to the principal features of the local geology that are accessible by a 2WD vehicle, in most cases followed by a short walk. All stops are marked on a clear, centre-fold road map in which roads and tracks are classified according to their accessibility. The documentation of each stop opens with a single sentence explaining the feature(s) to be seen, followed by a paragraph on access (including parking and any issues about private property) and with the decimal latitudes and longitudes. Thereafter the features at the stop are described in detail, in most cases accompanied by a photograph. Of particular value to those organising excursions for groups is a summary table at the end which lists the vehicle access (small or large bus, 4WD), parking, walking distance and permissions required for each stop.
The first eight stops are on the plateau, the remainder are close nearby. Stop 14 is a geological traverse along the Tallarook-Yea highway, with over 25 features of interest identified and odometer readings from Tallarook provided. Detailed highway guides, with features of interest and odometer readings, are also provided for those travelling to Tallarook from Melbourne or Benalla via the Hume Freeway.
The booklet ends with a short section on the sport of rogaining, which was ‘born’ in the forests of the Tallarook Plateau. An additional section deals briefly with the vegetation on the plateau. For those wishing to bring themselves up to speed on the basics of igneous petrology the booklet ends with a nicely illustrated essay entitled ‘Geology 101’. Unusually for a field guide, there is also a short but very useful index.
Geology of the Tallarook Plateau is a must-have for anyone with even a remote interest in the beautiful Tallarook area and/or cordierite granites and their occurrence in one of Australia’s classic geological terranes.