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Geology
The Tootgarook Swamp is situated in a depression that is surrounded by the edge of The Cups late Pleistocene aeolian sediments in the west, to the Boneo Plain dunefield of the early Pleistocene aeolian sediments in the east and north-west, and to the Rosebud dunefield of the early Pleistocene aeolian sediments in the north-east.[1]
The Tootgarook Swamp was formed in an ancient Pleistocene (Ice Age) tideway that was blocked by dunes. Silts and clays were deposited along these tideways, such as the so-called marls on which the peat rests in the Tootgarook Swamp.[2]
There are no permanent watercourses on the Nepean Peninsula; the dune rock is too porous to hold meteoric and fluviatile waters. The bottom of The Cups are sometimes covered with swamp grasses but never with water. Flood water coming down the blunted scarp of Selwyn Fault has scoured out channels in the dune-rock at the foot of the scarp, as for example the lower reaches of Drum Drum Alloc Creek, but these only carry water while the flooding lasts; an hour after it subsides the channels of the water course are quite dry.[3] A number of underground flows exist along the length of the Selwyn fault to the east feeding the swamps hydrology after passing through the Boneo flats.
Only a few depressions on the Nepean Peninsula hold water. They are the Tootgarook Swamp near Rosebud and some small swamps west of Sorrento. The clay or marl, as it was described by Sir Frederick Chapman (1919), that held the water in the Tootgarook Swamp is impervious. The peat there was formed in shallow water, the level and composition which influenced the decay of vegetable matter. The swamp occupies the channel of the old Tootgarook Tideway, the entrance of which to Port Phillip has been cut off by a small bay-bar (Juston 1931). The so-called marl is doubtless silt deposited in the tideway similar to the silt dredged from the tideways of Port Phillip.[3]
The Tootgarook Tideway is a former channel of which can be easily discerned from a point of vantage on Arthur's Seat and which is now partly occupied by the Tootgarook Swamp; it had an outlet to Bass Strait about 3 miles north-west of Cape Schanck. Sir Frederick Chapman (1919) identified a number of fossils from a shell-marl in the swamp. He listed both marine and freshwater species and suggested that the marine shells indicated some antiquity, a Pleistocene age. The level of the Swamp is under 20 feet above sea-level and the presence of the marine shells could possibly be due to the transgression of the Post-glacial high sea-level.
[1] vro.dpi.vic.gov.au/dpi/vro/portregn.nsf/pages/port_soil_landforms_tootgarook, - Department of Primary Industry Victoria Australia
[2] The Mornington Peninsula, Memoir 17 - R.A. Keble 1950.
[3] Memoirs of the Geological Survey of Victoria - R.A. Keble 1950
The Tootgarook Swamp was formed in an ancient Pleistocene (Ice Age) tideway that was blocked by dunes. Silts and clays were deposited along these tideways, such as the so-called marls on which the peat rests in the Tootgarook Swamp.[2]
There are no permanent watercourses on the Nepean Peninsula; the dune rock is too porous to hold meteoric and fluviatile waters. The bottom of The Cups are sometimes covered with swamp grasses but never with water. Flood water coming down the blunted scarp of Selwyn Fault has scoured out channels in the dune-rock at the foot of the scarp, as for example the lower reaches of Drum Drum Alloc Creek, but these only carry water while the flooding lasts; an hour after it subsides the channels of the water course are quite dry.[3] A number of underground flows exist along the length of the Selwyn fault to the east feeding the swamps hydrology after passing through the Boneo flats.
Only a few depressions on the Nepean Peninsula hold water. They are the Tootgarook Swamp near Rosebud and some small swamps west of Sorrento. The clay or marl, as it was described by Sir Frederick Chapman (1919), that held the water in the Tootgarook Swamp is impervious. The peat there was formed in shallow water, the level and composition which influenced the decay of vegetable matter. The swamp occupies the channel of the old Tootgarook Tideway, the entrance of which to Port Phillip has been cut off by a small bay-bar (Juston 1931). The so-called marl is doubtless silt deposited in the tideway similar to the silt dredged from the tideways of Port Phillip.[3]
The Tootgarook Tideway is a former channel of which can be easily discerned from a point of vantage on Arthur's Seat and which is now partly occupied by the Tootgarook Swamp; it had an outlet to Bass Strait about 3 miles north-west of Cape Schanck. Sir Frederick Chapman (1919) identified a number of fossils from a shell-marl in the swamp. He listed both marine and freshwater species and suggested that the marine shells indicated some antiquity, a Pleistocene age. The level of the Swamp is under 20 feet above sea-level and the presence of the marine shells could possibly be due to the transgression of the Post-glacial high sea-level.
[1] vro.dpi.vic.gov.au/dpi/vro/portregn.nsf/pages/port_soil_landforms_tootgarook, - Department of Primary Industry Victoria Australia
[2] The Mornington Peninsula, Memoir 17 - R.A. Keble 1950.
[3] Memoirs of the Geological Survey of Victoria - R.A. Keble 1950
