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Home , Cape Sorell, Cat Island (Tasmania), Macquarie Harbour, Macquarie island, Trial Harbour

THE OF Resource, Management and Conservation Division Department of Primary Industries, Parks, Water and Environment THE ISLANDS OF GPO Box 44 , , 7001 MACQUARIE HARBOUR

Hamish Saunders Memorial Survey Program 2009

HAMISH SAUNDERS MEMORIAL TRUST,

Editors Michael Pemberton and Clare Hawkins

Department of Primary Industries, Parks, Water and Environment CITATION: Pemberton, M., Hawkins, C. (2011). THE ISLANDS OF MACQUARIE HARBOUR. Hamish Saunders Memorial Trust, New Zealand and Resource Management and Conservation Division, DPIPWE, Hobart, Nature Conservation Report Series 11/01

ISBN (Book): 978-0-7246-6567-9 ISBN (Web): 978-0-7246-6568-6

A partnership program between the Hamish Saunders Memorial Trust, New Zealand and Resource Management and Conservation Division, DPIPWE, Tasmania.

DESIGN AND LAYOUT: ILS Design Unit, DPIPWE ILLUSTRATIONS: Brett Littleton OBJECTS PHOTOGRAPHY: Graeme Harrington, Tasphoto Services, DPIPWE COVER: Narrow cobble beach on the east coast of Neck Island. Photo Paul Donaldson. INSIDE COVER: Lighthouse. Photo Brett Littleton.

© Department of Primary Industries, Parks, Water and Environment, 2011.

This publication is printed on recycled paper.

COPYRIGHT This work is copyright. It may be reproduced for study, research or training purposes subject to an acknowledgement of the sources and no commercial use or sale. Requests and enquiries concerning reproduction and rights should be addressed to the Resource Management and Conservation Division, DPIPWE or the Hamish Saunders Memorial Trust, Auckland, New Zealand. THE ISLANDS OF MACQUARIE HARBOUR

Hamish Saunders Memorial Island Survey Program 2009

HAMISH SAUNDERS MEMORIAL TRUST, NEW ZEALAND

DEPARTMENT OF PRIMARY INDUSTRIES, PARKS, WATER AND ENVIRONMENT

Editors Michael Pemberton and Clare Hawkins TABLE OF CONTENTS Hamish Saunders Memorial Island Survey Program 2009 3

TABLE OF CONTENTS 3

FOREWORD 5

Hamish Saunders 6

Acknowledgements 6

Summary of Results 7

INTRODUCTION 9

NEW ZEALAND VOLUNTEER REPORTS 13

GEODIVERSITY 19

BIODIVERSITY 37

Flora 37

Fauna 73 FOREWORD Hamish Saunders Memorial Island Survey Program 2009 5

The Hamish Saunders Memorial Island Survey Program was established in 2005 as a result of a partnership agreement between the and the Hamish Saunders Memorial Trust following the tragic loss of Hamish while assisting in a conservation survey on , an island about 20 km south of Tasmania in 2003.

The aim of the program is to Islands play an important role in survey an island each year to nature conservation given they collect information on natural can be remote and difficult to values which will contribute to the access providing natural barriers management and conservation to some threats. Their remoteness of these islands. The survey also means that there is a lack conducted in 2009 in Macquarie of data for these places so the Harbour was the fourth in Hamish Saunders Memorial Trust a series of multi disciplinary Program provides the perfect investigations following work on opportunity to collect information , Three Hummock that can contribute to island Island and Prime Seal Island in conservation but also provide a previous years. lasting legacy to Hamish Saunders.

The Hamish Saunders Memorial Like past surveys the Survey Program provides Harbour Islands survey has important information on island resulted in the collection of conservation but is also a great a wide range of information opportunity for conservation which will assist in the future scientists, including two New management of these important Zealand volunteers, to visit an places. island for about a week and work cooperatively to assess the natural diversity of these places.

Alistair Scott

General Manager, Resource Management and Conservation Department of Primary Industries, Parks, Water and Environment 6 Hamish Saunders Memorial Island Survey Program 2009

Hamish Saunders natural world and conservation Acknowledgements with that of an interest in local Hamish Saunders was a cultures and people. Not only did The Hamish Saunders Memorial New Zealand volunteer who he travel to these places, but he Trust is acknowledged for taking died tragically in 2003 while also took a great interest in the part in the survey. In particular conducting survey work on a people around him. He touched Alan and David Saunders who Tasmanian endangered species many lives. manage the trust in New Zealand program. Hamish graduated and who assisted with the from Waikato University with a Hamish was a remarkable and selection of the two volunteers First Class Honours and Masters talented young man. The passion from New Zealand Briar Hill and degree in marine geology. He and enthusiasm he engendered Natasha Wilson, thanks to you all. later completed a postgraduate in those whom he met and the GIS course with distinction. He gentle leadership he embodied Chris Arthur, Parks and Reserves also achieved qualifications as a is his legacy. This island survey Manager, West Coast who scuba dive instructor, was a good program is dedicated to the suggested the Macquarie Harbour sportsman and was talented, not memory of Hamish Saunders Survey and assisted with the solely academically, but as an all and intended as a platform for logistics and operational side. His round individual. emerging leaders in marine expert boatmanship was also conservation. The Tasmanian appreciated. As an explorer, Hamish achieved Government’s commitment in his 26 years much of which and long-term support for the For assistance in the preparation most only dream. From program was endorsed by the of the geodiversity section, thanks to the Galapagos, Central then Minister for Environment and to Mike Comfort, Rolan Eberhard America, South America, South- Planning, The Hon. Judy Jackson and Jason Bradbury for their East Asia, Europe and , MHA, on 8 July 2005. editing and comments on drafts; he combined his passion for the Greg Jordan for his thoughts on plant fossil significance; and all others involved in the islands of Macquarie Harbour expedition.

For flora support thanks to David Storey for his assistance with data analysis, Tim Rudman and Micah Visoiu for their help identifying flora species.

For support in the component, thanks to Bob Mesibov: millipede and centipede identification; Kevin Bonham: snails, collembola identification; Michael Driessen: cave cricket and rodent identification; Lynne Forster: spider and beetle identification; Hamish Saunders Memorial Island Survey Program 2009 7

Fox Eradication Branch for the Biodiversity – Vegetation been recorded in Macquarie loan of video cameras; Tracey Harbour. Of the newly recorded Hollings for loan of hair tubes; A total of fifteen discrete TASVEG taxa, forty-nine were identified Robert Raven (Queensland vegetation communities were to species level and thirty- Museum): spider identification; recorded during the survey. three were identified as distinct Alastair Richardson: isopod and Of these 3 were Threatened morphospecies, while the rest amphipod identification ; Michael communities listed on Schedule were identified less precisely. Rix (Western Australian Museum): 3a of the Nature Conservation Numerous bird species had Micropholcomma and Hickmanapsis Act (2002). The most significant previously been recorded in spider identification; Barbara Triggs: community was MSP (Sphagnum ‘Macquarie Harbour’, but the mammalian hair identification; peatland) as there are only survey provided more specific finally Stephen Harris is thanked two other known sites for this locations for many of these for his final edit of this report. community at sea level. species.

Summary of Results A total of 122 vascular flora Isopod specimens of the genus species from 56 families were Notoniscus found on three of Geodiversity recorded across the islands the islands were likely to be a surveyed. The species are new species. The findings also The islands of Macquarie comprised of 50 higher plants particularly extended the known Harbour are geologically and (7 monocots and 44 dicots) distribution of two invertebrates: geomorphologically diverse. and 13 lower plants. Of the the land snail Stenacapha species recorded, 14 are endemic vitrinaformis and the weevil The islands are composed of to Australia; 1 occurs only in Mandalotus subterraneus. either poorly consolidated Tasmania. Eighteen species are Tertiary gravels, semi-lithified considered to be primitive. There A few exotic species were Tertiary sandstone or Cambrian were 24 introduced species found identified: most significantly, hair to Precambrian meta-sedimentary with 9 of these being listed weeds. tubes collected hair that was basement rocks. One orchid species was found confirmed as cat hair on Philips that was not known to occur in Island, and suspected as cat hair The morphology of the islands are the south west of the state and on . heavily influenced by their lithology, this discovery has considerably ranging from low-lying gravel increased the known range of A sea eagle’s nest was found on islands bound by narrow cobble this species. All vascular species Philips Island. beaches and extensive marshlands recorded are either represented It is recommended that cat to steep bedrock islands with in reserves in each bioregion or eradication is considered, and dominantly cliffed coastlines and are reserved in half the bioregions that disturbance on Philips Island rocky shore platforms. within which they occur. is avoided during eagle breeding An array of earth features of Biodiversity - Fauna season (July to February). interest are dispersed throughout the islands, of which a number One hundred and sixty fauna are to be considered for listing in taxa were recorded during the the Tasmanian Geoconservation survey, of which one hundred Database (TGD). and thirty-two had not previously INTRODUCTION Hamish Saunders Memorial Island Survey Program 2009 9

Macquarie Harbour is located on the central west coast of Tasmania. It has a number of islands and nine of which were surveyed over a five day period from the 7th to the 11th December 2009.

The overall form and shape of the harbours current form was This reflects the complex geology Macquarie Harbour region was in place. This left the islands and of the area and the climatic probably well developed by coastline we see today. variations which occur as a result about 40 to 50 million years ago of proximity to the coast and in early Tertiary times. Many of Many of the plant species in changing altitudes. the major mountain and valley south western Tasmania and systems evident today in the around Macquarie Harbour have A recent discovery at area, and in the rest of Tasmania, evolved directly from species is the Port Davey skate which also were probably formed by this that occurred in Gondwana (the occurs in Macquarie Harbour. This time following the breakup of southern super continent) about species is unique as the world’s Gondwana. This resulted in 45 million years ago. The more only brackish water skate, and the development of the broad rugged and mountainous parts has its closest relatives in New valley system now flooded by of south eastern Australia and in Zealand and Patagonia again the harbour’s dark waters with particular Tasmania remained the emphasising the Gondwanan link. sediment provided by the Gordon “most Gondwanan”. Here the River and its tributaries eroding cool, damp climate remained highland areas as far away as Lake similar to the temperate St Clair and the Vale of Rasselas. forests of Gondwana. However there are Macquarie Harbour has had a many other vegetation history of being drained and types represented flooded over the last 2 million in the area ranging years as a result of various from button glaciations and ensuing sea level grass moorland, fluctuations. heathland, a range of wet The mouth of the eucalypt was about 20 km out to sea forest types around 20 000 years ago at to coastal the height of the last glaciation. scrub. Glaciers and small ice caps in the catchment started melting after this and by about 6000 years ago 10 Hamish Saunders Memorial Island Survey Program 2009

Macquarie Harbour islands locality map. Base map: 1:100,000 map, insert maps: 1:25,000 map (reproduced courtesy of TASMAP, DPIPWE). Map produced by Paul Donaldson. Hamish Saunders Memorial Island Survey Program 2009 11

With the exception of Sarah Macquarie Harbour has a oceanic Island there has been very limited climate with rainfall spread survey work done on the natural throughout the year with a mean values of the islands in Macquarie annual average of about 1500 Harbour. The Hamish Saunders mm. Daily maximum summer Memorial Island Survey Program temperatures vary between offered an ideal opportunity for a 18.9 and 21.5°C with overnight multi-disciplinary group of experts minimums averaging between 9.3 to visit the area to investigate and 11.2°C. Winter maximum conservation and management daily temperatures average needs of these islands. between 12.2 and 13.2°C with overnight minimums averaging between 5 and 6.1°C. NEW ZEALAND VOLUNTEERS REPORT Hamish Saunders Memorial Island Survey Program 2009 13

Briar Hill We spent the first few days acquainting ourselves with Hobart, Getting There including a cruise on the harbour, visiting the weekend markets and I have been studying ecology and going to the movies. We also conservation for 7 years, and it got taken to the top of Mount has always been my plan to take Wellington, which allowed us to my love for the environment really appreciate the surrounding overseas. When I saw an ad for landscape. Clare Hawkins, who the Hamish Saunders Memorial we were staying with and who Ecological Survey, I applied straight away. It was a while before I heard back and as I got more and more distracted with my research, I forgot about the application. This meant that when I did find out that I had been selected for the Macquarie Island trip, it came as a complete and fantastic surprise. At that time I was experiencing some setbacks with my research, and being given the chance to get away and remind myself why it is that I am doing what I’m doing was so invaluable and allowed me to return to my was also organising the trip, got studies full of enthusiasm and with Natasha and I to help with the a fresh perspective. preparation and packing for the trip; this was fantastic as it gave The preparation for the trip us a chance to become familiar happened very quickly, and with the gear that was to be used before I knew it I was landing in before getting into the field. Melbourne where I met up with Natasha. We got to know each The Island Ecological other before making our way Survey to Hobart, where on arrival we were collected by Mick Illowski Many of the islands within the and taken back to the DPIWE Macquarie Harbour formed office to meet everyone and part of the Macquarie Penal get a briefing on the trip. I was Station during the early 19th overwhelmed at how welcoming century, and was known as one everyone was and how excited of the most notorious and harsh they all were about the trip. penal settlements. Once closed, 14 Hamish Saunders Memorial Island Survey Program 2009

however, the islands were never Over a 5 day period eight of the collecting them in and finding re-occupied and have been left many islands were surveyed by that we had set them correctly virtually untouched since the mid the team of seven scientists. It and managed to capture videos 1800’s. It is only in recent years was the most surreal feeling being to show us what was creeping that tourism has taken off in the on these small islands, knowing around at night. The craziest area, with Sarah Island drawing that few people had been there part of the trip was being filmed thousands of visitors each year to and that until then many of the by ABC, ending up on the news see the old prisons, and Bonnet islands had been left untouched months later, and having an Island now open to tourists for by science. Natasha and I were Australian friend of mine call me viewing. This increase on bug duty. On our first day we up to tell me she had just seen in visitation is a concern as little were left to it and being New me on TV - world famous! is known about the ecological, Zealanders, believing that Australia geological and biological value of is full of snakes, we walked very Personal experiences the islands within the Harbour. slowly and cautiously on that first This trip provided so many The ecological survey undertaken day. It wasn’t until the following amazing experiences, above therefore aimed to investigate day on Philips Island that we all meeting the other scientists the flora, fauna and geology of observed the others thrashing who participated in the trip numerous small islands within through the forest and realised we from whom I learnt invaluable the Macquarie Harbour. The had been a bit too cautious the knowledge and skills; including purpose of this was to establish day before. Lesson learned; we setting hair traps and camera an inventory to help guide better moved a lot faster from then on. traps and learning the saying management and protection of that has now shaped my thesis the islands in the face of increasing The bush was very similar to “absence of evidence is not development. New Zealand, with tree ferns creating a canopy above and evidence of absence”. There was The weather forecast for the ground ferns covering the forest such a vast amount of knowledge, week was not too great, but floor below, and it was easy to enthusiasm and laughter on that didn’t dampen anyone’s forget where you were until you the trip that it was impossible spirits, so on the 7th December spotted an enormous Eucalyptus not to leave feeling completely the boot clad group of 7 took tree towering overhead. The bugs rejuvenated and ready to tackle off from Hobart and drove to also made sure you didn’t forget the world. Being a part of this Strahan. The drive alone was where you were and never in a survey has strengthened my amazing, getting to travel across blue moon did I imagine that I desire to take my skills overseas Tasmania with some of the most would ever roll around on the and experience more new and experienced scientists narrating forest floor in Australia lifting logs exciting environments beyond local history, biology and politics and digging dirt trying to find the New Zealand, and one day to in the background. When we biggest blackest spider, and then be able to make a significant arrived in Strahan we were yelling screams of joy when I did! contribution to the protection of briefed by Chris Arthur (Parks New Zealand’s natural heritage. and Reserves Manager, West By far the most rewarding part I owe an enormous thank Coast - the man with ALL the of the trip was setting out the you to the Hamish Saunders knowledge!), and then it was motion cameras on numerous Memorial Trust for continuing straight out into the field. islands and then a few days later Hamish’s legacy in this way and Hamish Saunders Memorial Island Survey Program 2009 15

providing this opportunity not on the natural biota to help with animal scat (taking photos of any only for myself but for those identification whilst in the field. interesting finds and collecting before and after me. It truly is Other than that, everything was droppings) and set up hair tubes an opportunity of a life time for fantastic! and camera traps. such young scientists to be able to take their skills and knowledge Natasha Wilson Every island was unique. With overseas and expand on them a total of nine islands in the at such an early stage. Thanks Six months have passed since I survey of Macquarie Harbour, a are also due to all the people at set foot on Tasmania and entered diverse array of flora, fauna and DPIWE and Chris Arthur who a whole new world. Now topography were found. As part made this trip possible and so whenever I see a stray gum tree of the animal species survey team, enjoyable. In particular to Clare or hear an Aussie accent, the our main priority was to be on the Hawkins for taking us in and memories come flooding back. lookout for anything animal, but making our stay fantastic, and Nick A whole week was spent going as our eyes tuned in to all weird Mooney, who provided us with back and forth between islands, and wonderful things we had the so much insight into the natural collecting specimens and setting pleasure of discovering several heritage of Tasmania and also the traps. As part of the animal delicate tree orchids and observing rare opportunity to get up close species survey team, I helped the amazing bark forms on the and personal with devils, quolls collect numerous insects in jars various gum tree varieties. Some and brown falcons. Finally to my (whatever we could find under islands were covered in thick bush volunteer buddy Natasha; thanks tree bark, crawling on the ground that reminded me of any North for all the laughter on the trip! or flying through the air), searched Island forest, but had the added the ground for burrows and danger of snakes and spiders. Improvements that could be made

It would have been great to have a better brief of the dates for the trip prior to booking the flights. As we were not informed of the survey itinerary until only a couple of days prior to departing New Zealand, we were not able to organise any extended time within Tasmania to explore more after the trip to Macquarie Harbour. This was a shame as it felt very rushed getting back from the field and having only an evening before heading home again. From the Tasmanian end, it also would have been great to have been provided with more resources 16 Hamish Saunders Memorial Island Survey Program 2009

As foreigners in the land, Briar and The entire week was one great the possibility of extending plant I quickly developed a wariness of adventure that guaranteed distribution ranges or finding new all moving things. We only saw a wealth of knowledge and animal species still exists. With an one small snake on the whole conservation ideas for the ongoing interest in conservation trip though. Spiders kept us future. It was a rare insight and ecological research, I hope on our toes a bit more as we into the biology of old; the way to use the knowledge and had no idea which ones were naturalists made discoveries and skills I’ve learnt to continue the poisonous and which weren’t. documented new lands. Being preservation of species for future We learnt one thing for certain one of the first to survey an generations. – never put spiders together in area, like Elizabeth Island, is an the same specimen jar. Several amazing thing and not common Without the support of the of our smaller specimens were in the world today. I gained an Hamish Saunders Memorial consumed or well wrapped up enormous appreciation for the Trust, this amazing experience by the time we got back to the conservation work that goes on in wouldn’t have been part of my base in Strahan at night. One Tasmania and the difficulties they life. Universities have such a large particularly large spider attacked encounter from both mining and portion of learning focussed on its neighbour with its large fangs disease. theories and books that it is easy and we were thankful it hadn’t to forget the field opportunities landed on either of us. Who Clare Hawkins, our lead zoologist, that lie in wait. What better knows what could’ve happened. ensured we knew as much as way is there to understand possible about the project at and expand your knowledge of With a full team of zoologists, hand and how different trapping conservation than to get out in botanists and geologists it methods worked that we hadn’t the field and see for yourself? The was easy to learn a lot about used before. It was my first many differences and similarities Tasmanian flora, fauna and experience using both hair traps that exist between New Zealand topography. Each and every and camera traps but with a quick and Tasmanian bush make you person had something to share. explanation and demonstration think that if there are that many Not only did we learn about the we were ready to go. Many of different species within similar islands, we learnt about Australian our camera traps that returned landscapes, conservation on a wildlife in general. Nick Mooney with dark video footage for global scale really is a diverse field was particularly keen to show the night sections were a waiting for further exploration, off his nature-bound backyard. disappointment but reinforced the research and management. We saw Tasmanian devils as part need to double-check the setup of the breeding program that’s was working on all cameras. I think this program provides in place. We saw wedge-tailed the perfect opportunity for eagles that were preparing for I learnt many important things young New Zealanders to get release back into the wild. We from the whole trip. Not only out and explore conservation in saw two different kinds of quoll. how to set and use new types of another part of the world. It is And to top it all off, we saw traps but also the types of work inspirational to work with such a dozens of potoroos and other conservationists may come across knowledgeable group of people types of wallaby. in the field. It is exciting to know who all share a strong passion that there are still places that for the environment and do their remain relatively unexplored with best on a daily basis to preserve it Hamish Saunders Memorial Island Survey Program 2009 17

for future generations. It has been And finally, I would like to a useful and insightful journey thank the Hamish Saunders that will act as a good foundation Memorial Trust, and all of the for future study and work in the people involved on the Tasmania ecological field. side of things as well, for this memorable experience that will For future volunteers I set me in good stead for future recommend: conservation work and hopefully further research and a life-long • Providing the opportunity to career in meeting conservation extend the flight back to New needs in both Tasmania and Zealand by a couple of days further afield. I hope to continue as many people in the Wildlife the tradition of passing knowledge Department offered to show onto others in this field, both now us more things and areas of and in the future. conservation interest if we had time. An agreement could be made for volunteers to meet the costs of any extra day’s accommodation and food, and pay for any extra cost incurred with a delayed return.

• Advertising this amazing opportunity in universities, particularly Zoology and Ecology departments GEODIVERSITY Hamish Saunders Memorial Island Survey Program 2009 19

The Cap Island, Macquarie Harbour. One of the many small islands dispersed throughout the harbour. Photo Paul Donaldson.

Paul Donaldson Macquarie Harbour forms islands with dominantly rocky Tasmania’s largest estuary system coastlines. The variation between Introduction with an area greater than 290 the islands morphology results km 2 (Edgar et al., 1999). The largely from their geological Over 25 islands of varying size are mouth of the harbour (Hells differences. Broadly, the islands can dispersed throughout Macquarie Gates) opens into the high energy be divided into three geological Harbour on the west coast of coastline of the west coast, groups: Tasmania. Geologically, the harbour through a shallow and narrow • the suite of north-western is situated within the Macquarie channel positioned between islands composed of Tertiary Graben, a large down faulted the northern tip of Cape Sorell gravels; structure which formed from Peninsula and the southern end of regional tectonic activity during spit. The restricted • the central-eastern islands the Early Tertiary in association opening results in little ocean composed of semi-lithified with rifting between Australia swell entering the harbour and a Tertiary sandstone; and and Antarctica (Stacey and Berry, tidal range of less than one metre. The harbour is generally a low 2004). The Macquarie Graben is • the chain of Cambrian to energy environment. However a bound by uplifted older basement Precambrian bedrock islands fetch of up to 30 km along the rocks to the south and filled positioned along the south- harbours northwest-southeast with a thick sequence of semi to western shoreline of the axis commonly results in the unconsolidated Eocene marginal Harbour. marine sediments (Baillie and generation of a locally derived Hudspeth, 1989), of an inferred choppy wind swell. Currents Together, these islands thickness of greater than 500 m in the harbour are complex comprise an array of geological, (Leaman, 1974). The northwest- and variable, dominated by geomorphological and soil southeast trending graben is the Gordon River in the south features of interest, of which 10-12 km wide over most of its and in the north only the Sarah Island sea caves length. It includes Ocean Beach (Koehnken, 1996). Evidence for are at present recognised for spit and the general area of the complex hydrodynamics of their conservation significance. Strahan in the north, Macquarie the Harbour is seen in the coastal A number of these features do Harbour and its many associated morphology of a number of the however warrant consideration islands within the central basin harbours island shorelines. for listing in the Tasmanian and extends south of the Harbour, Geoconservation The geomorphology of narrowing to 6 km in a southern Database (TGD). the Macquarie Harbour dog-leg section which includes islands is variable, Birches Inlet (Corbett, 2003). It is ranging from low- both the south-western bedrock lying islands bound boundary of the graben and the by narrow cobble sub-aerial exposures of the thick beaches and sedimentary infill which comprise extensive the geological base of the marshlands, Macquarie Harbour islands. to steep bedrock 20 Hamish Saunders Memorial Island Survey Program 2009

Methods Results/Discussion Geomorphology:

A reconnaissance study Bonnet Island Bonnet Island is a small, of the island geology and ovate bedrock island with an geomorphology of Macquarie Geology: approximate north-south axis of Harbour was undertaken for 65 m, east-west axis of 30 m and Bonnet Island comprises a single eight of the harbours largest an maximum elevation of 10 m outcrop of metamorphosed islands over a period of five days above mean sea-level (MSL). The sedimentary (metasedimentary) in December 2009. Each island island’s rocky coastline varies from rocks. This metasedimentary survey consisted of brief field a narrow shore platform with sequence includes a succession examinations (typically three to abundant rocky debris, to low- of interbedded metamorphosed five hours for each surveyed lying cliffs which plunge steeply quartz sandstone and siltstone, island), focussing on the coastline into the sea. Abundant burrows and forms part of the more morphology, bedrock exposures, are found throughout the soils extensive geological unit that known sites of geoconservation of the island, formed by the occupies the northern extent of significance (Sarah Island sea resident colony of Little . Cape Sorell. This unit is known as caves) and additional features of The surface morphology of the the Mesoproterozoic Rocky Cape interest as interpreted through island centre has undergone Group Correlate (Corbett, 2003). analysis of satellite imagery (e.g. both historic and recent Neck Island tombolo). The islands anthropogenic modification as surveyed were Bonnet, Cat, a result of historic farming by Elizabeth, Magazine, Neck, Philips, past resident lighthouse keepers Sarah and Soldiers Island. Access and the recent development of to the islands was by the PWS tourist infrastructure that includes boat Shearwater. multiple viewing platforms and a central gravel pathway.

Bonnet Island, Macquarie Harbour. Photo Paul Donaldson. Hamish Saunders Memorial Island Survey Program 2009 21

Earth features of interest/ cross-bedding on Bonnet Island Management issues significance: was noted by the Geological Survey of Tasmania as “well Observations made across the • Herringbone sedimentary developed..., large scale (100- island suggest that the upgraded structures 300 mm)... and indicative of very walking paths have resulted in shallow water deposition” (Baillie the concentration of surface Large scale herringbone cross- and Corbett, 1985). As such, the water runoff down slope of the bedding sedimentary structures outcrop is considered to be of newly gravelled paths. This is are well preserved in the significance for its size, exposure likely contributing to the localised naturally outcropping sequence and its representative value for erosion which was observed along the eastern coastline of this depositional process. This adjacent to the viewing platforms. Bonnet Island. This sedimentary feature is also indicative of the structure formed in a subaqueous geological setting for which the environment where tidal currents metasedimentary Rocky Cape periodically change direction, Group Correlate of the Sorell thus resulting in the deposition Peninsula was deposited. of cross beds dipping in opposite directions. The herringbone

Well developed, large scale herringbone cross-stratification on the eastern side of Bonnet Island (note the camera lens cap for scale). Photo Paul Donaldson. 22 Hamish Saunders Memorial Island Survey Program 2009

Cat Island Geomorphology: Earth features of interest/ significance: Geology: Cat Island is a low lying irregularly shaped island with an • Cobble spit Cat Island is composed of a clast approximate north-south axis supported pebble to cobble of 600 m, east-west axis of 630 A narrow cobble to pebble conglomerate sequence with m, and a maximum elevation spit forms at the southern a variable sandy component. of 4 m above MSL. The island is coastline of the island, diverging The unit consists of poorly composed of poorly consolidated perpendicularly from the coast consolidated, non marine sediments, with narrow pebble to for ~100 m. The sediment sandy gravels, likely Tertiary in cobble beaches to the east and composition and geomorphic age. Sediments include well extensive marshland to the west setting of this spit makes this rounded, poorly sorted quartzite, which forms intermittent, irregular landform unique, as pebble sandstone and siliceous gravels. marshy embayment’s. The islands to cobble spits and spits of This island forms part of the coastline is commonly scarped, a sheltered origin are both Macquarie Beds, a thick semi- providing a local source of uncommon landforms in a consolidated sedimentary sediment to the adjacent cobble Tasmanian context. sequence which occupies much of beaches. A sandy organic soil layer

the Macquarie Graben (Baillie and of varying thickness covers the Corbett, 1985). island. This is well exposed along

the scarped shoreline.

Left: A satallite image of Cat Island. The non marine cobble spit is located in the south-western corner of the island. (bottom left). 2005 SPOT satellite image, courtesy of TASMAP, DPIPWE

Right: Narrow cobble to pebble beach, Cat Island cobble spit. Photo Paul Donaldson.

Hamish Saunders Memorial Island Survey Program 2009 23

Elizabeth Island MSL. The shoreline is mostly the complex polydeformational steep, descending to a rocky coast history of the region. However, Geology: with regular boulder size slope it should be noted that these deposits. A number of small coves structures are a common feature The geology of Elizabeth Island is are found around the island, one of the Rocky Cape Group composed of a deformed siliceous containing a narrow gravel beach Correlate (R. Berry 2010, pers. metasedimentary sequence, which and another housing a small sea comm.), thus their value is forms part of the Cape Sorell cave. The island centre is steep primarily at an aesthetical level. Mesoproterozoic Rocky Cape and undulating with a number of Group Correlate. The geology well exposed outcrops. • Sea cave of Elizabeth Island is structurally complex. The rock sequence is Earth features of interest/ The small shallow sea cave on the strongly foliated with abundant significance: western coast of the island is a well formed deformation textures structurally controlled erosional outcropping along the northern • Deformation structures feature. The cave forms a raised coast. and inactive landform at present, Deformation structures are well with a base of 1 - 2 m above Geomorphology: exposed on bedrock outcrop MSL. This erosional feature likely throughout the northern formed at a time when Elizabeth Elizabeth Island is a small bedrock coastline. Structures observed Island was exposed to marine island with an approximate include complex folding, quartz swell and/or at a time of relative north-south axis of 230 m and vein en echelon arrays and higher sea-level. an east-west axis of 145 m, and crenulations cleavage. These rises steadily out of the harbour structures are a striking example to an elevation of 23 m above of their type and are indicative of

Elizabeth Island, Macquarie Harbour. Photo Paul Donaldson. 24 Hamish Saunders Memorial Island Survey Program 2009

Small, shallow joint controlled sea cave on the west coast of Elizabeth Island (note backpack in left midground for scale). The base of this cave is raised above the high tide mark, indicating that it formed at higher relative sea-level.

Quartz en echelon array at Elizabeth Island. Cavities in the semi-brittle rock form through shear tension as a result of regional deformation. Quartz crystals grow incrementally as cavities are formed. This feature is indicative of a localised shear zone.

Crenulation cleavage development in the metasediments, resulting from multiple deformation events. All photos Paul Donaldson. Hamish Saunders Memorial Island Survey Program 2009 25

Magazine Island m, a northeast-southwest axis Neck Island of 100 m and an elevation of up Geology: to 5 m above MSL. The island Geology: coast varies from dominantly Similar to Cat Island, Magazine narrow south facing cobble to Neck Island is composed of a Island is composed of a poorly pebble shorelines, to thick organic weakly consolidated pebble to sorted conglomerate sequence rich marsh deposits along the cobble conglomerate sequence of the Tertiary Macquarie northern coast. The island body within the Tertiary Macquarie Beds. Sediments are primarily is largely flat with a thin layer of Beds. The sequence includes composed of poorly sorted, organic rich soils mantling the poorly sorted, well rounded, well rounded, siliceous pebble to surface, interspersed with cobble sandstone, quartzite and siliceous cobble clasts with a variably sandy to gravel size siliceous clasts. These conglomerate clasts with a sandy matrix. soils are heavily bioturbated in matrix. places. Historic shallow earth Geomorphology: Geomorphology: works and building remains are Magazine Island is a small, low common in the central west of Neck Island has a unique planform lying Island with an approximate the island, including handmade shape, consisting of a central northwest-southeast axis of 250 bricks and a footing for a building body of approximately 400 m

Left: Narrow cobble beach on the east coast of Neck Island, Macquarie Harbour. Photo Paul Donaldson.

Right: Narrow gravel beach, Magazine Isalnd. Photo Natasha Wilson. 26 Hamish Saunders Memorial Island Survey Program 2009

in width, extending south into a Earth features of interest/ the northeast shore from both a narrow neck for over 1200 m. significance: southerly and northerly direction. The island is mostly low lying Individually, these two spit like with a maximum elevation of 6 m • Longshore drift derived features are largely uncommon in above MSL. The shoreline line is pebble to cobble coastline. a Tasmanian context due to their dominated by long, narrow gravel sediment composition (primarily Neck Island’s shoreline comprises beaches to the east and thick well rounded, siliceous, cobbles), two distinctive longshore drift marsh deposits overlying a gravel shoreline morphology and aligned pebble to cobble deposits, base to the west. A blanket of soil formation in sheltered, low energy including: a narrow, north-south and gravel cover the central body environments. directed tombolo which connects of the island. the southerly neck of the island • Prograded cobble berm coast. Neck Island has diverse shoreline to the mainland; and the near morphology. The southern neck symmetrical, triangular spit like A set of shore parallel pebble of the island forms a thin gravel feature, which protrudes west to cobble berms have deposited tombolo which connects the from the main body of the island. along the northern coast of Neck island to the mainland at the The tombolo is approximately Island. The berms form a set of distal end of Ocean Beach spit. 100 m in length, narrows to only steeply stacked narrow ridges. The northern end of the Island a few metres wide and adjoins This depositional feature is a good includes a triangular ‘cuspate the recurved hook of Ocean example of a locally prograding foreland’ like spit which protrudes Beach Spit enclosing Swan Basin. coast, with each berm ridge likely west from the islands centre; a This low lying feature is primarily formed in a single depositional (? set of well developed prograded composed of well rounded storm) event. pebble to cobble beach berms; pebble to cobble sized clasts • Buried soil. and a well exposed buried soil and is more formally defined horizon, overlain by a gravelly as a tie-bar, due to its partial A buried fibrous organic rich soil mixture. These features are submergence at high-tide (Bird, soil horizon, overlain by a layer detailed below. 2008). The triangular spit like of pebbly soil is well exposed feature has formed by wave/tide on the eroding west coast of action approaching at an angle to Neck Island. The buried organic soil layer is approximately 15 cm thick and has formed on a pebble Shoreline erosion at mooring site adjacent the shack at Neck Island. to cobble base. This unit is well Photo Paul Donaldson. developed and thus indicative of a significant period of stable paleoenvironmental conditions. The upper boundary of the buried soil forms a sharp, and likely erosional, contact with the overlying deposit, suggesting that the poorly sorted pebbly soil layer was deposited during a high energy (?storm) event. This well Hamish Saunders Memorial Island Survey Program 2009 27

Clockwise from top left: Siliceous cobble to sandy deposits of Neck Island. This poorly consolidated unit comprises a conglomerate sequence of the (? Tertiary) Macquarie Beds. The geology of Cat and Magazine Island comprise the same, or a very similar sequence (note pencil for scale). Pebble to cobble tombolo, connecting Neck Island to the mainland. Photo is looking south with Neck Island in the foreground, the tie bar in the mid-ground and Ocean Beach spit in background. Palaeosol overlain by a gravelly soil layer on the north western shore of Neck Island (note pencil for scale). A set of sub parallel prograded cobble beach berms on the north coast of Neck Island, indicative of a seaward building coastline. All photos Paul Donaldson. 28 Hamish Saunders Memorial Island Survey Program 2009

exposed feature is indicative of adjacent the shack is obviously Philips Island local paleoenvironmental change. used by visitors for mooring boats. This has lead to the Geology: Management issues erosion of the inherently unstable marshy coastline. Philips Island is primarily A shack is located within a small composed of a semiconsolidated cleared area on the island. The • Tree cutting for fire wood. interbedded sandstone and human impacts from its use There is evidence for siltstone sequence with minor include: firewood collection within coal beds. The basal carbonaceous the vicinity of the shack. This sandstone unit is well consolidated • Local foreshore erosion: is causing degradation of the and highly fossiliferous. A small section of marshy adjacent bush. coastline on the west coast Geomorphology:

Philips Island forms the tallest island within Macquarie Harbour, rising sharply from the shore to a maximum elevation of 41 m above MSL. The island has an ovoid shape with an approximate east-west axis of 530 m and north-south axis of 200m. The northern coast is dominated by a rocky platform composed of fossiliferous carbonaceous sandstone boulders. The southern coastline is dominated by a steep to cliffed shoreline, exposing the semi consolidated sedimentary sequence. Historic earth works and terracing occurs within the island as a result of earlier pig farming practices.

Top: Fossiliferous well consolidated sandstone boulders, with plant stem impressions. North coast of Philips Island. Photo Paul Donaldson.

Bottom: Coalified unit (possible tree stump ?) within a carbonaceous sandstone boulder. North coast of Philips Island. Photo Paul Donaldson. Hamish Saunders Memorial Island Survey Program 2009 29

Earth features of interest/ Sarah Island siliciclastic, with abundant quartz significance: grains in the sandstone units. Geology: The sub-vertical beds are north • Fossiliferous sandstone striking, young to the east and boulders Geologically Sarah Island is contain regular load structures. composed of an interbedded Sarah Island forms part of the Fossiliferous sandstone boulders siltstone and sandstone larger Noddy Creek Volcanics and form a narrow shore platform sedimentary sequence of correlates, a volcano-sedimentary along the northern coast of Philips Cambrian age (Corbett, 2003). sequence of the eastern Sorell Island. The well consolidated The sequence is predominately Peninsular region (Corbett, 2003). boulders contain fossil flora including plant stems and leaf impressions of which the taxa are unidentified. Tertiary sediments throughout this region are known to be commonly fossiliferous (G. Jordan 2010, pers. comm.), however the age and significance of the plant fossil site at Philips Island is unknown.

Sea caves on the west coast of Sarah Island have developed along plains of weakness within the Cambrian bedrock. Development of this sea cave initiated through preferential erosion of the finer grained (siltstone) sub-vertical sedimentary bed. Photo Paul Donaldson. 30 Hamish Saunders Memorial Island Survey Program 2009

Geomorphology: Earth features of interest/ passage including species of the significance: genus Micropathus (M. Driessen Sarah Island forms a lensoidal 2010, pers. comm.). shaped island with an • Sarah Island Sea Caves approximately northeast- An array of secondary mineral southwest axis of 650 m, Multiple sea caves of variable coatings and crystal growths of northwest-southeast axis of 165 size and morphology are located varying mineralogy, colours and m and a maximum elevation of on the west facing coast of textures have formed throughout 18 m above MSL. The islands Sarah Island. The geometry of the cave, including a ferruginous morphology is structurally the many caves are structurally drip water speleothem, multiple controlled with the north striking, controlled, largely forming along small radiating needle like sub-vertical sedimentary beds the north striking sub vertical crystal growths (frostwork forming abundant northerly bedding plain of the outcropping speleothem) and abundant small facing coves which back onto geological unit. The Sarah Island nodular concretions of unknown a north trending hilly terrain. Sea Caves were initially reported mineralogy. The formation of these The island has a predominantly by Bradbury (pers. comm. types of secondary features in a steep rocky coastline, with minor 1995, in Dixon, 1996) and have non carbonate geological unit is sandy beaches located on the been subsequently listed in the an unusual phenomenon and thus southeast coast. The northeast Tasmanian Geoconservation contributes to the conservation coast comprises plunging rocky Database as an outstanding significance of the Sarah Island cliffs with interspersed with geomorphological site of local Sea Caves. deep narrow coves, rocky shore significance (Dixon, 1996). The platforms and cobble to boulder most well developed cave of the • Sea Arch deposits. A sea arch and multiple island will be briefly described A sea arch is located within the sea caves of varying sizes have below. central western coast Sarah also formed along this coastline The largest and most Island. This feature consists of (detailed below). geomorphologically diverse a rounded 2 m wide, 3 m long, Sarah Island has the longest sea cave on Sarah Island is opening through the sandstone history of human occupation approximately 20 m long, 8 m sea cliffs. Tafone (“honeycomb”) of the Macquarie Harbour wide and is located at the foot of weathering has developed on the islands, and as such, exhibits the a steep sea cliff approximately 1 - internal walls of the arch, forming most modified landscape of 2 m above MSL. Two west facing cavernous weathering hollows the islands visited at Macquarie entrances access a long, linear, low of variable size. Sedimentary Harbour. Deforestation, building lying passage which is orientated structures are well exposed construction and general in a northerly direction. Collapse on the outer wall of the arch. earthworks including terracing of the outer cliff has partially These structures are common and quarrying occurred covered the southern entrance throughout the island (discussed throughout the history of the and adjacent floor of the cave. below). Sarah Island penal station in The remainder of the cave floor is • Sedimentary structures the early to mid 1800’s. Many mantled by layer of organic matter, historic remains of the infamous including soil and abundant woody Sedimentary load structures settlement are present today. debris. Large cave crickets were were regularly observed along observed on the roof of the main Hamish Saunders Memorial Island Survey Program 2009 31

the Cambrian interbedded silt to sandstone sequence, on the west coast of Sarah Island. Load structures form at the time of deposition as a result of differential soft sediment compaction. Flame structures are a specific type of load structure which are common throughout the sequence, resulting from an injection of the underlying finer bed up into the overlying coarser bed during compaction. These structures are indicative of both the depositional environment and younging direction of the sedimentary sequence.

Top: Main passage of largest sea cave at Sarah Island. Note the ferruginous speleothem in the top right of the photo.

Middle: Cave crickets, including the genus Micropathus, on the roof of the large sea cave, Sarah Island.

Bottom: Sub centimetre frostwork speleothems (middle of photo) and nodular concretions (top right of photo) of unknown mineralogy, on the roof of the large Sarah Island sea cave. All photos Paul Donaldson. 32 Hamish Saunders Memorial Island Survey Program 2009

Soldiers Island Geomorphology: cliffs dominate the south west coastline. The semi consolidated Geology: Soldiers Island has a unique sediments which make up the duck like planform, up to 700 m island show signs of structural Soldiers Island is composed of long on a northeast–southwest instability, with wide spread semi consolidated sandstone axis and up to 450 m wide. The slumping commonly observed sequence which forms part of terrain is low lying in the north along the cliffed shoreline. A the greater Macquarie Beds. The and rises steadily in the far south number of intertidal sea notches sequence dips slightly to the to a maximum elevation of 21 m have formed in the south eastern north and is well exposed along above MSL. The island is largely cliffs. sea cliffs at the southern tip of the fringed by coastal marsh deposits, island. however, tall sub-vertical sea Earth features of interest/ significance:

• Soldiers Island intertidal notches

A number of intertidal notches have been cut into the semi- consolidated sandstone sea-cliffs at Soldier Island. The series of notches were observed locally along the southeast coast at varying levels within the present tidal range. The abundance of notches observed within a small area along the cliffed coast suggests that further notches may be present along the Soldiers Island coast. Intertidal notches have been widely used as a geomorphic indicator of past relative sea-levels. As such, this coastline warrants further investigation.

Sea arch, Sarah Island. Photo Paul Donaldson. Hamish Saunders Memorial Island Survey Program 2009 33

Conclusion Soldiers Island, has resulted The similarities within and in an east-west strike ridge diversity between each group, The islands of Macquarie dominating the topographic highlight the influence of Harbour are geologically and highpoints of the island as well underlying geology on the islands geomorphologically diverse. The as the formation of steep and geomorphology, most notably geodiversity of the islands are actively cliffing shorelines along their coastal morphology. attributed to a combination of sections of their variable lithology and structure southern coast. of the underlying geology and on past and present geomorphic • The rocky processes. Broad geomorphic shore platforms similarities are readily observed steep plunging between the islands of a similar bedrock cliffs geological composition. These and structurally include: controlled earth features (e.g. • The longshore drift aligned sea caves) are coastlines have formed in common to the low lying, unconsolidated the Cambrian Tertiary gravel islands, to Precambrian including Neck, Cat and bedrock islands, Magazine Island; including Bonnet, Elizabeth and • The gently northerly dipping Sarah Island. strata of the semi-lithified Tertiary sandstone Philips and

Above: Load structures in the Cambrian sedimentary sequence, resulting from differential soft sediment compaction at the time of deposition. Here the underlying finer unit (bottom) has injected into the overlying coarser sand unit (top) in a flame like pattern (note hand lens for scale).

Left: Intertidal notches cut into the foot of the semi-consolidated sandstone cliffs at Soldiers Island. Photos Paul Donaldson. 34 Hamish Saunders Memorial Island Survey Program 2009

The number of features identified during the island survey indicate Management Recommendations that the Macquarie Harbour islands have a geomorphic history Tasmanian Geoconservation Database (TGD) which includes both past and recommendations: present processes. For example, the well developed and slightly The geodiversity of the Macquarie Harbour islands include raised sea cave at Sarah Island a range of geological and geomorphological features which suggests that the islands present are well developed, uncommon and/or of potential scientific shoreline morphology has formed significance. As such, a number of earth features identified over a period which predates the throughout the 2009 Hamish Saunders islands survey are present sea-level. The age of the deemed worthy of nomination for listing within the TGD. These caves are not known, however features/sites are listed below. their formation presumably dates back to at least the last interglacial • Neck Island’s coastal geomorphology. The island as a stage. Locally raised coastlines whole should be considered for listing due to the diversity are also known to also exist of coastal features which have formed in a sheltered within the greater Macquarie environment. Harbour region, including relic beach deposits within the Ocean • Fossiliferous sandstone boulders on Philips Island. These Beach spit which have been fossil rich boulders have the potential to be of geological attributed to a last interglacial significance, to help better constrain the deposition history age (Banks et al., 1977). The more of the Macquarie Harbour Graben. recent geomorphic features of • Cat Island cobble spit. The Cat Island spit is an uncommon the islands, including the pebble geomorphic feature at the regional scale. to cobble beaches and marshy coastlines, have however formed Also, the current Sarah Island sea caves listing should be in their present state since the updated with additional descriptive information as detailed in culmination of the rising sea- this report. level to its present level some 6000-7000 years ago (Lambeck The following recommendations are made in relation to a and Nakada, 1990; Sloss et al., number of the management issues identified in the field: 2007). Much of this younger coastline shows evidence for • The present shoreline erosion observed on Neck Island continued reworking (e.g. Neck should be documented/mapped and any further erosion Island buried soil horizon), due monitored. If erosion continues, consideration should to the combination of locally be made into the construction of a low impact mooring derived waves, tidal fluctuations structure. and variable harbour currents, indicating that the islands • The impact from surface water runoff from the newly coastlines are continuing to gravelled pathways at Bonnet Island should be monitored, as evolve. there is the potential for an erosion issue to develop. Hamish Saunders Memorial Island Survey Program 2009 35

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