Cenozoic conifer wood from the Gore Lignite Measures, Southland, New Zealand

Abstract

Well preserved fossil wood in the form of tree stumps, logs, branches, roots and occasionally bark is common throughout the Gore Lignite Measures, southern New Zealand. The main objective of the present study is to identify the range of forest trees present using anatomical features such as: distinct growth rings; presence or absence of axial parenchyma; uniseriate to triseriate, opposite to alternate, separate or contiguous tracheid pitting; and taxodioid, cupressoid and araucarioid cross-field pitting. Specimens of silicified and lignified wood are described and illustrated from four localities within the Late Oligocene–Early Miocene Gore Lignite Measures, Southland: Newvale Coal Mine; Mataura Coal Mine; Cosy Dell Coal Pit; and Bennett’s Pit. The fossil wood specimens include examples of Araucariaceae, Cupressaceae and Podocarpaceae. Three specimens from Newvale Mine resemble Araucariaceae, while one is assigned to Cupressaceae. Cosy Dell Coal Pit preserved branches of Podocarpaceae. Large stumps and branches preserved at the Mataura Coal Mine are identified as Cupressaceae and Podocarpaceae. Wood recovered from Bennett’s Pit resembles either Cupressaceae or Podocarpaceae. Araucariaceae, in the form of Agathis Salisb. trees are today restricted to the northern North Island. Cupressaceae and Podocarpaceae are still extant in modern forests throughout New Zealand. So far, no angiosperm wood has been recognised from the lignite deposits. The forests in which these trees lived were in or near oligotrophic swamps on a deltaic plain. Identification of samples of fossil wood provides new data that can be used to reconstruct the forest vegetation of the Gore Lignite Measures.