February 8, 2011

To study or not to study: a Metamorphic Genesis or a Dynamic Creek?

Lately I've been thinking about what topic I should choose for doing my senior undergraduate major project. This project is essentially worth 3 credits, or one full course. The synopsis outlines it as almost a thesis but with a narrower scope of time, and only to be peer reviewed by my university professors. I'm planning on it for this semester next year, but want to utilize the coming summer months for field work.

The first idea that comes to mind is to measure/analyze something local. I don't want to synthesize and regurgitate some phenomenon that is a world away where I can't put my hands on it (I do that enough on this blog). After all, one of the big reasons I chose geology is because on occasion the laboratory is the great outdoors. The second thing that comes to mind is that I want to break new ground. Not by finding new analytical methods or a stunning new hypothesis (I won't have the time, funds, knowledge nor experience to do that for several years), but by covering something in greater detail than has been.

I might have access to basic hydrological equipment: current meter plus pH, conductivity, and DO probes. In that case I wish to study the fluvial geomorphology of a particular large creek that has not had a thoroughly holistic study. Plus my favorite geology book is Leopold's, and this would give me an excuse to read it again. Its geomorphology is of particular interest because the creek cut a channel down through glacial till and exposed a volcanic basalt layer underneath, thus a small portion of its mid-reaches has step-pool falls. More details found in the earthcache I created for it.
Cliff falls in Maple Ridge, BC. Kanaka creek pinches
here due to eroding down to a resistant lava flow
If access to equipment or most of the drainage basin is not possible, I am considering doing a petrological study of a pre-Jurassic [mostly] metamorphic group on the north shore. There is surprisingly little information about it, beyond a few journal papers making slight references to it when describing other groups/formations that interact with it. This would involve a thorough investigation of approximately 8 sites of varying size (see map below) where outcrops have been identified, plus I'd get to use snazzy terms like aureoles and metamorphic facies. All I'd need in that case is a rockhammer, a handlens, maybe a petrographic microscope.
Surficial geology map of North & West Vancouver
#1 is the Twin Islands Group I'm considering for study
I'll likely put this on the back burner until late spring, when I will have time to investigate the creek and gauge how I can approach it from various access points. In the meantime, professorial advice and anecdotes will likely sway me towards one or the other.

Terminology note: It took me a while to wrap my head around the phenomenon of roof pendants. Sometimes a blatantly obvious mechanism or concept eludes me, until a light bulb goes on. This has happened with things like pedimentation, cyclothems, Benioff zone.  My best attempt to explain to myself the idea of roof pendants - When a batholith forms below overlying strata, it penetrates upwards, and thus makes contact with those layers. The layers will likely undergo contact metamorphism, and metamorphose under high temperature & low-moderate pressure. Erosion of subsequent material leaves the META members as isolated crops dangling/resting above the batholith. Essentially roof pendants have a parent rock, and are akin to xenoliths on a large scale but did not get included into the igneous mass, simply resting above it instead.

Additional Info:

1 comment:

Elli said...

If you went with the met pet, you'll definitely want to at least use the petrographic microscope. But most modern petrologic studies will also involve chemical analyses either with the SEM with WDS or a electron microprobe. The unit description has a huge variety of potential protoliths, so it might be very interesting...