Shingle Beach Ridges EarthCache
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Difficulty:
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Terrain:
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Size: 
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These Shingle Beach Ridges are of ancient geologic history. Please
apply lowest impact not to destroy them - drive your car only on
the official tracks signposted as such. Park your car and walk
the last few meters. Future generations will thank you.
Shingle
A Geological Phenomenon [1,2]
These stranded shingle beach deposits of moderately sorted, rounded
an sub-angular pebbles and cobbles which form flat topped ridges
XXX meters above present mean sea level, rarely more than 10m
– 15m wide, have been traced over some 50km from near the
head of Spencer Gulf southwards along its western shore to Stony
Point, and can be clearly seen north of Fitzgerald Bay. They
provide a distinctive geological feature which is believed to date
back to the Pleistocene period. It appears, that the combination of
a heigher sea level, strong easterly winds, and high energy wave
dissipation along the shoreline were responsible for the deposits
which are the only ones in South Australia.
Beach ridges occur worldwide and are accumulation of sediments
deposited on wave dominant, low gradient coasts. These
geomorphological features occur in different forms, such as barrier
islands enclosing a lagoon, or ridges attached to a mainland cliff.
Deposits can range from sand, gravel, shells, pebble and
shingle.
View over the bay
History of Fitzgerald Bay [2,3]
Baie Corneille
Fitzgerald Bay was first navigated by Matthew Flinders in March
1802, followed by Frenchman Louis-Claude de Freycinet in January
1803. Freycinet explored the Spencer Gulf on board the Australian
built ship Casuarina. Turning down at the head of the gulf,
Freycinet battled strong winds and shallow waters for nearly 60 h
before he sailed past Fitzgerald Bay and anchored just behind Point
Lowly.
He named Fitzgerald Bay ad Baie Corneille and described it as a
large bay with weak anchorage. Although planned, he did not explore
the hills behind the bay, nor its geocaches, due to a lack of
time.
Aquaculture
The first fish farms were established at Baie Corneille in 1998.
They initially specialized in snapper, changing to yellow tail
kingfish specie in recent years. The industry supplies both
domestic and international markets.
Fitzgerald Bay
Questions to claim the cache:
Q1: With your GPS, measure the width of the deposit from base to
base at GZ
Q2: Estimate the height of the ridge above surrounding flat
ground
Q3: What is the height of the ridges above current mean sea
level?
Q4: How big are the shingles, describe them
Q5: Describe the consistency of the sand in the beach nearby. What
is it made of?
Q6: Where do you see similar, modern deposits in the vicinity.
Describe. Photo?
Q7: Take a photograph with you and your GPS and upload it
(optional)
References:
[1] ”Northern Coastline”, Whyalla City Council
(http://whyalla.com)
[2] ”Freycinet Trail” (signposted), Whyalla City
Council (http://whyalla.com).
[3] Paul Mazourek: ”Early Maritime Heritage of Northern
Spencer Gulf”, Whyalla
Maritime Museum 2005, (download).
Further Reading:
Nick Harvey: “Holocene Coastal Evolution: Barriers, Beach
Ridges, and Tidal Flats of South Australia”, Journal of
Coastal Research, 2006; 22 (1):90-99. doi: 10.2112/05A-0008.1
Sérgio Dillenburg, Patrick Hesp: “Coastal Barriers –
An Introduction”, in “Geology and Geomorphology
of Holocene Coastal Barriers of Brazil”, Lecture Notes in
Earth Sciences, Springer Berlin / Heidelberg, 2009, Volume
107/2009, 1-15, doi: 10.1007/978-3-540-44771-9_1
Across the Spencer Gulf
Additional Hints
(Decrypt)
Orfg lbh trg urer! Lbh pna pnzc bire avtug naq unir rabhtu gvzr gb rkcyber.
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