Please find below provisional overviews of the proposed field trips.

Please check this page regularly; it will be updated with field trip prices and minimum numbers required to proceed once finalised.

Field Trips will be available to book from June. If you register before they are available, we will email you when bookings open. You will be able to log back into your record and add any that you are interested in.

If you wish to discuss a field trip or require further details, please email the contact person whose details are listed below.

Pre-Convention Field Trip

Geology of North-East Tasmania

Geological Overview:
Eastern Tasmania is usually considered to have a basement terrane with a quite separate origin to western Tasmania. It is often correlated with the Melbourne zone of the Lachlan Fold Belt in Victoria, although this is still arguable. The basement comprises turbidite-hosted siliceous sediments of the Mathinna Supergroup, of Ordovician to early Devonian age. These are intruded by numerous Late Devonian – Early Carboniferous granitic batholiths and related igneous rocks. These intrusions are locally accompanied by Sn-W mineralisation of varying styles. There are also numerous small to medium sized gold deposits of mesothermal/turbidite-hosted vein style, similar to the Victorian goldfields. These rocks are locally covered by the Parmeener supergroup sediments of Late Carboniferous – Triassic age, thick Jurassic dolerite intrusions, and Cenozoic basalts and sediments; the Cenozoic sediments locally have rich alluvial tin and/or gold deposits. To the west this eastern Tasmania terrane is juxtaposed with the Western Tasmania terrane (Proterozoic to Late Devonian), in a structure known as the Tamar fracture zone, probably active from the Cambrian to the Cenozoic. Some of this structure can be seen in the Beaconsfield area, where there is a melange of Cambrian ultramafics, with diverse slivers of Precambrian to possibly Siluro-Devonian sediments. This site also includes the famous Beaconsfield gold mine. The trip will see most of the above-mentioned formations and mineralisation types in some very spectacular coastal and mountain settings.

Expected Itinerary:
Coles Bay, Bicheno, St Marys, Rossarden, Mangana, Mathina, Blessington, Scottsdale, Bridport, Lefroy, Beechford, Badger Head and Beaconsfield.

Duration:
3 days

Contact person:
Ralph Bottrill
ralph.bottrill@stategrowth.tas.gov.au

Mid-Convention Field Trips

Cape Raoul - Tasman Peninsula Cruise

Tasman Peninsula by Sea

Geological Overview:
South-eastern Tasmania is largely underlain by horizontal to gently dipping beds of sandstone, siltstone, limestome and coal. These rocks, dating from the Permian and Triassic were later intruded by bodies of Jurassic dolerite (183 million years ago) which formed sheets between layers of sedimentary rocks. This was a widespread phenomena covering over one third of Tasmania, and possibly more in the past. This intrusion also affected Antarctica, Argentina and South Africa. This has been called the Karoo-Ferrar large igneous province. Three to five million cubic kilometres of magma were intruded overall. The magma cooled to form columnar dolerite, which have been eroded to form sea stacks all around the coastline of Tasman Peninsula.

Expected Itinerary:
Bus trip from Hobart with boat cruise along the coast to take in the impressive dolerite cliffs with Pennicott Wilderness cruises.

Duration:
1 day

Contact person:
Grace Cumming
grace.cumming@stategrowth.tas.gov.au

Tasman Peninsula by Land

Geological Overview:
South-eastern Tasmania is largely underlain by horizontal to gently dipping beds of sandstone, siltstone, limestome and coal. These rocks, dating from the Permian and Triassic were later intruded by bodies of Jurassic dolerite (183 million years ago) which formed sheets between layers of sedimentary rocks. Faulting in the Early Cenozoic produced several major grabens with intervening uplifted areas. The Oyster Bay Graben, formed at this time, extends along the east coast from the Tasman Peninsula through to St Marys. Basaltic volcanic centres in the Saltwater River on the Tasman Peninsula erupted during the Paleogene.

As sea levels fell during the glacial stages of the Pleistocene (125,000 – 20,000 years ago) rivers cut valleys to levels below the current sea level. The melting of ice sheets, about 10,000 years ago, resulted in a rise in sea level, forming the current drowned coastline features evident over much of southeast Tasmania.

Duration:
1 day

Contact person:
Phil Sansom
psansom@iinet.net.au

Cygnet Alkaline Complex

Geological Overview:
Numerous small bodies of enigmatic suite of Cretaceous syenitic rocks intrude a Permo-Carboniferous shelf sequence and Jurassic dolerite in one of Tasmania’s most picturesque coastal areas. They range from silica-saturated to moderately under-saturated compositions, with a diverse mineralogy, some spectacular textures and are associated with sub-economic gold mineralisation.

Expected Itinerary:
Mt Mary Mine, Petcheys Bay, Wheatleys Bay, SE of Wheatleys Bay, Copper Alley Bay, Langdons Point area, Robleys Point, Martins Point, Abels Bay

Duration:
1/2 day

Contact person:
John Everard
john.everard@stategrowth.tas.gov.au

Kunanyi / Mt Wellington – Geological features, periglacial features and natural hazards

Geological Overview:
Kunanyi’s impressive columnar dolerite rock formations, an isolated  basaltic centre, mass wasting features, history of landslides and periglacial features will form the focus of this field trip.

Expected Itinerary:
Follow the South Wellington Track from the Summit and traverse over the basalt volcanic centre, then branch onto the Zig Zag Track to take in the periglacial deposits and then head down to the intersection with the Pinnacle and Organ Pipes tracks. Here we turn right onto the Pinnacle Track and walk about 100m until meeting the 2014 rock fall boul-der. After this, stop and backtrack to the last intersection and then follow the Organ Pipes Track and take in the spectacular columnar dolerite below the summit, and walk to the Chalet.

Duration:
1/2 day

Contact person:
Colin Mazengarb
colin.mazengarb@stategrowth.tas.gov.au

Breakfast Field Trips

Blinking Billy Point

Geological Overview:
Eastern Tasmania is usually considered to have a basement terrane with one of the earliest geological investigations in Australia. The site includes some Cenozoic basalt flows, dykes and pyroclastic deposits, with some hydrothermal veins. There are also some Tertiary boulder beds, fossiliferous Permian sequences and some unusually laminated Jurassic dolerite intrusion. There are also some geotechnical/geohazard interest as much of the cliffline, especially the boulder beds, rich in variably weathered dolerite, is rapidly eroding and many houses on the clifftop look precarious.

Expected Itinerary:
Start from Beach Rd carpark, with stops at basalt and tuff beds, dolerite boulder beds, fossil and dropstone-rich Permian beds and banded dolerite outcrops.

Duration:
2 hours

Contact person:
Ralph Bottrill
ralph.bottrill@stategrowth.tas.gov.au

Hobart Rivulet Linear Park – Molle Street to Cascade Gardens

Geological Overview:
Leisurely morning stroll along the Hobart Rivulet Track. Triassic sandstones and Jurassic dolerite. An introduction to the ‘rocks that made Hobart’.

Expected Itinerary:
The group will leave from the start of the Rivulet Track at Hamlet Cafe (at the end of Collins Street, just SW of Molle Street). The walk will follow the course of the Rivulet as far as Cascade Gardens (Cascade Brewery). The Rivulet was an essential fresh water source for early Hobart, and subsequently, for the 19th Century for commercial operations and the Female Factory prison (now a UNESCO World Heritage Site). Along the way attendees will see glimpses of prehistoric dolerite debris deposits, as well as excellent bench and cliff exposures of Triassic fluvial sediments.

Duration:
2 hours

Contact person:
Peter McGoldrick
petergeologist@icloud.com

Post Convention Field Trips

Sisters Beach 1

NW Tasmania – exploring Tasmania’s Proterozoic rocks

Geological Overview:
Tasmania’s oldest rocks include the Rocky Cape Group. The remarkably well-preserved packages of rocks in NW Tasmania is considered to have once been attached to similar rocks in western North America between 1.45 billion and 1.33 billion years ago. Well preserved sedimentary features can be observed at Sisters Beach, Rocky Cape and far western Tasmania along the Tarkine Coast. Above the Rocky Cape Group, an uncomfortable boundary is marked by the Forest Conglomerate and the Donaldson Formation (West Head and Goat Island). The field trip will focus on notable outcrops of Rocky Cape Group, Forest Conglomerate and Oonah Fmn including dykes and syn-sedimentary intrusions.

Expected Itinerary:
Travel to NW Tasmania from Hobart. Stop at the Cooee Dolerite at Burnie, pillow lavas in the Oonah (old Burnie Fmn.), Goat Island Conglomerate, Sisters Beach (top of the Rocky Cape Group), Rocky Cape, Forest Conglomerate at West Head, upper-RCG at Bluff Hill Point, Cr-spinel bearing dykes/Lower RCG north of Temma. Final stop at the Horodyskia quarry before possible drop off at Wynyard, Launceston airports or return to Hobart.

Duration:
4 days

Contact person:
Grace Cumming
grace.cumming@stategrowth.tas.gov.au

Ore Deposits - Frenchmans Cap

Ore Deposits of NW Tasmania

Geological Overview:
The western Tasmania terrane is very complex but dominated by sedimentary sequences from the Middle Proterozoic to early Devonian in age. It includes many ophiolite complexes and an island-arc style, acid to mafic volcanic belt formed during early and mid-Cambrian continental collisions and subduction. Devonian granitoids intrude and underlie much of this terrane and have been responsible for much metamorphism, metasomatism and ore formation. There are three major episodes of economic mineralisation in the area: early Cambrian ultramafic-related PGM-Ni-Dr deposits (eg. Hazlewood); mid Cambrian volcanic-related Cu-Au-Ag-Pb-Zn-Ba deposits (e.g. Lyell, Rosebery, Henty), magnetite deposits (e.g. Savage River); and late Devonian granite-related Sn-W-Pb-Ag-Ni-magnetite deposits (e.g. Renison Bell, Avebury). These deposits lie in a spectacular mountainous landscape with dense forests and wild rivers.

Expected Itinerary:
Collingwood River, Mt Lyell, Trial Harbour, Zeehan Museum, Core-store visits, Mt Bischoff.

Duration:
4 days

Contact person:
Andrew McNeill
andrew.mcneill@stategrowth.tas.gov.au

Salt distribution in different parts of the Tamar landscape due to effects of deep bedrock weathering

Geological Overview:
Dryland salinity manifests as salt scalds, reduced pasture yield, salt efflorescence on roadside outcrops and impacts on built infrastructure (salt impacted brickwork, rising damp, damaged pipework etc.) and salty streams in the Greater Launceston Area (GLA) and surrounding rural landscapes. These influences of salinity are more apparent in some places than others, and the patterns of impact are not straight forward to interpret. In the urban area this means that salinity effects may occur in a section of one street but not in adjacent streets, be present in localised upland areas and have a wider distribution in lowland areas. It is apparent that some salt is emerging in areas underlain by Launceston Group paleo-estuarine sediments, and along the banks of the Tamar Estuary. But there are other localities that are impacted by salt where there is a dolerite substrate, not previously associated with salt storage and discharge. The patterns of distribution are further modified by neotectonic and geomorphic processes. Identifying the landscape setting of likely salt stores enables conceptual models for salt mobilisation to be developed. This provides an understanding of why salt impacts certain areas of existing suburbs, and indicates where ongoing management will need to be provided. It also helps predict where salt is likely to appear in the peri-urban landscape which informs planning.

Expected Itinerary:
Meander Valley, Hadspen, Prospectvale, Reid, Trevalyn, Riverside West, Lagana, Invermay, Rocherlea, Ravenswood, Norwood, Kingsmeadow, Punchbowl, East Launceston, Launceston CBD (Landslide).

Duration:
1-2 days

Contact person:
Leah Moore
leah.moore@anu.edu.au

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

As a broadly based professional society that aims to represent all Earth Science disciplines, the GSA attracts a wide diversity of members working in a similarly broad range of industries.

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