Randolph's Lots in a Day Series Introduction
This small grouping of caches has been placed so that the local cachers who are doing volunteer work at the Mega, and have probably already cleaned out their home town, can have a chance at getting some of their 15 types in a day.
It won't help them with the webcam, but some other types will be on offer.
(also for others who accidentally cleaned out the town before the Mega!)
Some Geology
The Wangaratta Mineral Area covers the northern section of the Melbourne, Walhalla-Woods Point and Tabberabbera gold zones and includes the major Rutherglen, Chiltern, Beechworth and Bright goldfields. Significant quantities of alluvial tin has been recovered from the Beechworth and Chiltern areas and alluvial diamonds are also reported from the Beechworth-Eldorado area.
We are not interested in the whole area (you only have one day!), just the area near the Mega's town of Wangaratta, in particular, the East Wangaratta NCR, and the rivers that surround ( and sometimes flood!) the park.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
It can be seen from this map that a good chunk of Wangaratta is built on the Alluvium 38485 area (the grey bits).
The three areas shown are described as follows:
alluvium 38485
Age: Holocene (0.0117 - 0 Ma)
Description: Channel and flood plain alluvium; gravel, sand, silt, clay; may be locally calcreted
Shepparton Formation
Age: Pliocene - Holocene (5.333 - 0 Ma)
Description: Unconsolidated to poorly consolidated mottled variegated clay, silty clay with lenses of polymictic (more than one more rock type), coarse to fine sand and gravel. Forms extensive flat alluvial floodplains.
Beechworth Granite
Age: Middle Devonian - Late Devonian (393.3 - 358.9 Ma)
Description: Strongly fractionated I-type granite with red-brown biotite with haloes
Placing a 1:25,000 map under this geological map shows some interesting features:
It can be seen that Reedy creek (in which the Eldorado Dredge can still be found) overlays the path of the grey area running east on the map.
Reedy Creek starts in the Beechworth Granite in the hills near Wooragee, flows through Woolshed Falls and continues down through Eldorado. It then follows the path shown on the map of the alluvium 38485, where it joins Yellow Creek and eventually flows into the Ovens River.
East Wangaratta Nature Conservation Reserve
This River Red Gum conservation reserve is two kilometers from the Wangaratta city center and can be accessed from a concealed gate along the Great Alpine Road, 400 meters east of the Yellow Creek bridge. A Parks Victoria sign marks the location.
Yellow Creek, an anabranch of the Ovens River runs along the reserve’s western boundary where it meets Reedy Creek.
An Anabranch?
An anabranch is a channel of water that leaves a river or stream and then rejoins again further downstream. An anabranch is considered to be part of the river or stream that it comes from. The word “anabranch” is more commonly used in Australia than in other parts of the English speaking world. Sometimes they are called Billabongs (if they are not permanent).
How are anabranches formed?
An anabranch can be very small, occurring as water flows along a river shore. Kids sometimes create temporary anabranches as they play on the shore. An anabranch can be nearly half of a river’s flow of water. When there is an island in the river, an anabranch is created as water passes around the island. The smaller channel of water passing the island is an anabranch of the river.
Are Anabranches Temporary or Permanent?
Some anabranches are temporary. They can happen during periods of heavy rainfall and flooding. Water may leave a river or stream and find its way back. An anabranch of the Darling River in New South Wales is 287 miles long and flows only during wetter months of the year. Other anabranches can be more permanent, such as water that passes around an island in the river. The water may slowly carry away sediment from the island, and the island may disappear after hundreds or thousands of years.
So it turns out that Yellow creek is an anabranch!
This Earth Cache will have you investigating this idea.
What to do
To complete this Earth cache you will need to visit at least two locations (or possibly three). The way points co-ordinates are listed below.
- WP1a is the confluence of Yellow Creek and Reedy Creek, and
- WP1b is the confluence of Yellow Creek and the Ovens River.
These will require you to park at the entrance to the East Wangaratta NCR and take a bit of a walk, then cross the road and walk into that park.
At times these way points will not be so easily accessible, for example after heavy rainfall. Sections of the park will go just over your gumboots (well they did over mine!), so I have provided another set of way points to try. All the second set are on major roads, it just requires a lot more travelling.
- WP2a is where Reedy Creek and Detour Road intersect,
- WP2b is where Reedy Creek and Bowser Road intersect, and
- WP2c is where Yellow Creek and the Great Alpine Road intersect.
To log this Earth cache you are required to email your answers and photos for the following questions to me.
1. If you use the confluences, record which directions all the rivers are flowing. (downstream is not an acceptable answer!). Take photos of the points of confluence.
2. If using the intersections, record which direction the rivers are flowing at those points (cardinal points are OK, ie: East to West). Take photos of Yellow Creek and the entrance to the park to show you couldn't enter without risking your gumbies going under!
3. Use this information to explain what is happening with all the water flows, and consider what this means for the flows of Yellow Creek, and why this makes Yellow Creek an anabranch.
4. Do you think that this anabranch is permanent or temporary, give reasons. Possible reasons could include building a large town right on the banks of the river, building levies to manage flooding, etc.
You can log this Earth Cache when you complete it to keep it in the right order, but if you have not sent your answers (and photos) within a week, your log will be deleted.