Thomson Museum Vic TPH774
PHANTOM FISH TRAPS
Stevens Island - to the north of Elcho Island in NE Arnhem Land
The Top End features monumental stone fish traps and a considerable amount of theory concerning their origin, antiquity and usage. Dark and geometric - these features in the littoral zone of clear, sunlit tropical waters, they appear as if stratified in an archaeological trench. Excavated by the sea, they have been widely interpreted as fish traps, despite local people consistently denying authorship - the absence of sufficient sedentary population to build and use such massive traps. This page critically examines the assumptions that underpin the theories and deconstructs examples of various types.
Stevens Is. & Australians Bay
The fortuitous placement of a crisp Google Earth tile, over the southern shore of Stevens Island, has provided a unique insight into the formation of these monumental stone structures. Appearing to have all the hallmarks of a fish trap in the dark rocks - rectilinear form of parallel lines & right angles - inundated at high and stranded at low water.
Stevens Island 'Slice of Luck' 10-2021 Google Earth
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Stevens Island Fish Trap Flip
SE shore Stevens Is. - Right Angle Break & parallel reefs NNW/SSE
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South Stevens Is. - 2 parallel lines
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Stevens Is. clean coronet
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Stevens Is. Inverted as a fish trap
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Australians Bay trap SE bay on Marchinbar Is. Wessel Islands NE Arnhem Land
Australians Bay Trap c40m wide
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Superimposition of Stevens Is. Coronet c110m wide
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Non-Mafic Dyke - Little Bondi - Baringura Inlet - East Arnhem Land
Makassan Finger Fish Trap - Inner Harbour - Melville Island.
Position re fish running out of creek - Tiwi call it Macassan Fish Trap - Located within a distributed Trepang Fishery Base - sufficient need for fish - smokehouses -
Nightcliff Fish Trap
Nightcliff Fish Trap looking SW to East Point - Port Darwin NT
Jesuit Mission - WW2
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Peron Islands Fish Trap
Chinese Fishing Village - image
Bentinck & Sweers Islands
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They are using handlines
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'Kaiadilt Aboriginal people traditionally use fishtraps at mid-tide' - The ladies are shown in the creek, fishing with handlines at high tide and are shown as proof of the use of fishtraps on the foreshore at mid-tide. It is obvious where the fish run as it is obvious that a population of perhaps 100 people could not build, use or maintain hundreds of kilometers of stonelines. There is amply documentation of the Kaiadilt foraging the inter-tidal zone at low tide which falls at night, from Matthew Flinders through to Tindale in mid-1960s.
Bentinck Island Gulf of Carpentaria QLD
Minette Dyke New Mexico USA
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Igneous compound dyke geograph.org.uk B. Bowyer - Isle of Arran Scotland
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The image at right is from the Isle of Arran in the Firth of Clyde - most remarkably it shows a dark ribbon of rock running through a lighter dyke.
International Traps for the Unwary
Wales medieval
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Poppit Sands Beach, Cardigan Wales
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Poppit Sands Beach, Cardigan Wales
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What sort of trap is permanently submerged. Why would the inshore arm of the ancient British fish trap not go directly to the adjacent outcrop of rocks to achieve the same or greater purpose?
Inverted River Channels and Volcanic Channels
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"When rivers deposit sediment in their channels and on the surrounding floodplains, the channel sediments usually have a larger grain size than the floodplain sediments. The channel sediments may also become strongly cemented after the area is buried. When these deposits are later eroded, the old floodplain sedimentary rocks are weaker and more easily eroded than the channel-fill rocks, which are left behind as a sinuous ridge, often called an inverted paleochannel. These features are common on Mars, where wind has blown away the fine-grained floodplain sediments. Understanding how these features form and are preserved on Earth helps to constrain the size of the rivers that formed them on Mars1. This project is a collaboration between the Planetary Science Institute and the Smithsonian.
Inverted paleochannels have been identified in many areas around the globe, but the ones in central Utah are outstanding examples. |
Inverted channels near Green River, Utah
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These paleochannels formed in the Late Jurassic and were buried by ~900 m of marine sediment during the Cretaceous, which experienced a global increase in sea level1. Only after ~75 million years of burial were the paleochannels exhumed during regional uplift in the middle to late Cenozoic1. The carbonate cementation of the channel sediments hardened them and enhanced their resistance to erosion. The less resistant surrounding valleys were eroded away, mostly by water rather than wind, leading to the current inverted state of the Utah paleochannels1.
Whereas most Martian river valleys are networks of tributaries, some emerge from a single pit or fault and appear to have an underground water source. Some of these valleys may have a volcanic origin, and we need a list of diagnostic features to tell lava and river channels apart. There are few large lava channels on Earth to compare with those on Mars. Our field sites include Iceland and Hawaii. This project is a collaboration between NASA Goddard Space Flight Center and the Smithsonian."
Whereas most Martian river valleys are networks of tributaries, some emerge from a single pit or fault and appear to have an underground water source. Some of these valleys may have a volcanic origin, and we need a list of diagnostic features to tell lava and river channels apart. There are few large lava channels on Earth to compare with those on Mars. Our field sites include Iceland and Hawaii. This project is a collaboration between NASA Goddard Space Flight Center and the Smithsonian."
Why are the channels wider at the bottom than the top - if the 'V' channel is solidified & the surrounding ground eroded it doesn't flip to a Pyramid. What are the boulders doing in silt? Occam's Razor would favour a Dyke Swarm as the simple solution.
Signature Traps
Taiwan trap - Pnghu Islands
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Necklace SE Tanimbars
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Fish Spear & Arrow Traps
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Kai Tulah modern arrow type
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