Places I've been: Inverloch Pt 2 - Chrono-turbation

The faulted cliff just to the east of the stairs has some very interesting sedimentary structures, the bulbous shapes in the middle of the above image. Each year, for the benefit of the students, we have a debate over the formation of these features. I tend to fall into the chrono-turbation camp. The basal shape of the structures suggests that the lower, unconsolidated, layer of mud was frozen (permafrost). When it was overlain by a denser mud, it eventually thawed and the heavier mud pushed down into the underlying sediment creating these bulbs.
The other camp is the bio-turbation camp.

If this were bio-turbation the 'burrows' are quite sizeable (digital camera case for scale), so either this is one kick-ass worm-critter, or the smaller dinosaurs were in the habit of digging burrows to a very uniform depth (which could also be explained by permafrost i guess). To me, the lack of fossilised bedding material rules out habitation burrows so if these were burrows they were temporary structures.

This image is of the structures, top down. While there isn't really enough exposure, I feel this looks more like weathered load casts than bio-turbation. I encourage you to visit the shore platform and the cliffs around Inverloch and make your own decision.

Next up: Fossils!

Places I've been: Inverloch Pt 1 - Structure

 

Looking all safe in my super-dooper safety vest!

Last weekend I participated in the annual pilgrimage to Inverloch with the first year geology students. This trip combines everything they've studied this semester into one convenient location - fossils, rock type identification and sedimentary rock naming conventions, sedimentary structures and current indicators and basic structural geology. I'm going to present some of the interesting things spotted at the site in the following posts, for now let's look at my favourite - structural geology!

Normal faulting with massive sandstone on the left and mudstone on the right	Fault drag locally bends the beds of the mudstone. Slicken can be seen in the sandstone on the left.

Most of the faulting is this region is normal and associated with the failed rift between Tasmania and Victoria which created the Bass Straight.

Shore platform faulting with fellow demonstrator for scale. A majority of these sedimentary beds are sandstone with occasional zones of scour and fill.	The extent of curvature in the sedimentary beds is more evident on the shore platform than in the cliff face. I've outlined the major faults but this region is riddled with them.

A close up of the faulted sandstone - Stay tuned for Park II - Chrono-turbation!

Bonus image - the demonstrating team from 2010 (Chris, Julie, Roland, Kim and I) with bonus beard, knitted and carpeted by my mother for my birthday, it was COLD that day!

Science with Amber

 

Spider in Amber shamelessly linked from here.

My interest in geology started with my Grandfather who still travels to Andamooka to mine opals. He used to go once a year and it was his private time away from his (in my opinion) huge family (5 kids + some ring-ins at times). When I was a child he would occasionally craft jewellery for us from opals or other crystalls that caught his attention. After many years of dabbling at University I finally found the geology department and started my own research. Once facet of this was to research how opals were formed so I could help him (theoretically) stake out his new patch each year.

During this time, he also taught me the basics of silver smithing. This combined with my interest in medieval things led me to play with amber. I recall one of my first attempts went horribly wrong. I had epoxied my cut and polished amber into a setting and chipped the stone while I was tightening the claws. So I thought I'd just dunk it in nail polish remover (like I did opals) to soften the epoxy and recut the stone. (clearly I wasn't thinking). The amber, being a resin, also went soft and squishy. Oops! I have toyed with the idea of seeing if I can soften amber, push inclusions like bugs into it (or squish two pieces together) and then re-harden them but I haven't gotten to that experiment yet.

 One of the experimental amber samples

In summary - I like amber, I like science and the following paper combines the two and may even help me in future purchases. Experimental studies on the heat treatment of Baltic amber. Yamei Wang, Mingxing Yang, and Yiping Yang. Gems & Gemology, Summer 2014, Vol. 50, No. 2

Timelapse of a river change course

Timelapse of a river changing course. I stole it from 9gag and who knows where they stole it from?

Date idea 8/10/2014 - Orbticular Diorite, Sweden

orbicular diorite - N57° 22.930 E15° 36.100

Counter top geology - Rapakivi granite

Large (up to 6cm) circular orthoclase feldspars (pink) phenocrysts with growth rings of opaque minerals (hornblende?). Many of the feldspars have a plagioclase feldspar (green) rim. Some also display a growth ring of plagioclase. The rest of the granite consists of large (1cm) crystals of dark minerals and orthoclase.

Small growth rim of plagioclase suggests alternating temperature/chemistry of the melt?

This granite is located on the side of Bran Diamonds on Swanston Street, Melbourne. It's one of my favourite facias in the city. I always thought it was a lovely weathered example of orbituclar granite however when confirming it's origin I found this page and this page both of which suggest this is in fact Rapakivi Granite.