The 12 Days of Cachemas (TDOC23) is a series of 78 caches, events and adventure labs placed across Victoria to celebrate Cachemas in July in 2023. The series is a joint initiative of Geocaching Victoria and the local community to release caches in a different category each day across the state. We hope you have as much fun finding this series as we had placing them. Now on to the cache.
On the second day of Cachemas, Signal gave to me,
two earthcaches,
and a wherigo up in a tree.
The Location
The Beaumaris Fossil Beach is located adjacent to, and just south east of, the Beaumaris Motor Yacht Squadron. The best idea is to park in the streets off Beach Road, in the vicinity of the Parking Waypoint, and then walk down the ramp to the BMYS.
You then follow the track at the base of the cliff, southwest on the Beach Road side of the BMYS. The track emerges at the Fossil Beach.
The Geology Lesson
The exposed rocks around here are sedimentary and were laid down in the following sequence.
The bottom visible layer here is the Fyansford Formation which was laid down about 10 million years ago, in the Miocene Epoch, and it is the oldest rock exposed around this area. This thin layer formed at the bottom of a warm shallow sea which resulted from a worldwide rising of sea levels known as a marine transgression. This layer has an extensive range of vertebrate fossils, including seal and penguin bones and shark teeth.
Over this, we have the Black Rock Sandstone, which was laid down in the late Miocene Epoch about 5 to 6 million years ago. This layer is exposed at many places around the bay's edge, between Point Ormond and Mentone. This layer is much thicker and contains vertebrate fossils such as bones and teeth at the bottom and, towards the top, the fossils of molluscs, echinoderms (sea urchins), corals, crustations and brachiopods (a type of shellfish).
And above these, we have the Red Bluff sands. This layer formed above water and is comprised of non-marine clay sands and gravel. It does, however, contain land animal fossils such as Diprotodon and Zygomaturus. It was laid down in the Pliocene Epoch 2 to 5 million years ago.
This is usually covered with a layer of surface soils and swampy sand dunes.
Now, the exciting thing here at this site is that we have ready access to see a cross-section of this geology because this area has been the location of a Monocline. You can gain an understanding of that subject by completing the excellent nearby Earthcache GC6M362 Beaumaris Monocline by PinkPiggy7.
My Finds
I have spent a little time sifting through the sands on the beach here and found a shark’s tooth and several sea urchin fossils. The best time to search is after recent storms. Snorkellers and scuba divers often make good finds too, as the formations are exposed out into the bay.
If you wish to search for fossils, it’s a good idea to bring a stool to sit on and comfortably sift through the sand and gravel between the water and the cliff. You are allowed to keep any fossils that you find, but you are not allowed to use an implement to dig on the beach or the cliffs (not a good idea anyway, from a safety viewpoint).
The Questions
Q1. Looking at the site's geology, why do you think the beach is a good place to find fossils lying in the sand?
Q2. Can you spot the different layers in the cliff at the end of the beach? What is the name of the thickest layer, and when was it laid down?
Q3. Please submit a photo with your log, including yourself or a personal object, and show the rocky breakwater at the BMYS end of the beach in the background.
General requirements.
As this is an Earhcache, you must submit your answers to me within 14 days, or your Find log may be deleted without notice.
You can use my profile contact details or preferably my email address at earthcaches@jamieson.id.au.
Sources
Weekend Geology .com
Beaumaris Conservation Society
I acknowledge the Boon Wurrung people as the Traditional Owners of the land upon which this Earthcache has been created.