Location: 2.7km south of Strahan, via the Esplanade and Lowana Road | Google Maps Reference
Key facts about this geosite:
• Exceptionally well-preserved fossil plant material from the Early Eocene
• The material was deposited during the Palaeocene-Eocene Thermal Maximum, a period of global warming 56 million years ago
• After this warm period, the sediments record evidence of a descent into severely cold “icehouse climate conditions” 34 million years ago
Geosite Description: Macquarie Harbour represents a flooded portion of a much older basin or half graben that developed during crustal extension during Paleogene (66 to 23 million years ago). The Macquarie Harbour Graben extends from the Moores Valley area north for about 100 kilometres to just south of Trial Harbour and is about 10 kilometres wide. The basin contains up to 800 metres of Paleogene sediments which record climatic fluctuations over the past 66 million years (Forsyth et. al., 2014). Poorly exposed Paleogene sediments of the Macquarie Harbour Formation may be viewed at several places in the Strahan and Regatta Point area.
During the Early Eocene (55 – 50 Ma) plant macrofossils and pollen were deposited in mudstones in several cuttings along Lowana Road. At the base of these sediments, fossilised leaves, fruits and stems can be found in angular mudstone clasts embedded in cobble rich deposits. Also present are Gymnostoma and a range of conifers and dicotyledons (eg, Eucryphia, relatives of the modern leatherwood). The site has relatively large exposures of fossil-bearing sediment.