Highly Allochthonous

Geological haikus

Sat, 15 Nov 2008 07:26:18 -0500

Things are, understandably, a bit busy for me at the moment. But a number of inter-flat hunt coffee breaks have given me the chance to scribble a couple of contributions to the haiku meme started by suvrat.

Have drill, will travel
The young geologist sighs,
Switching homes once more

Paleomagic.
A black box that very few
Choose to peer inside.

Many others have also revealed their hidden poetic depths:

Julia
Kim
Bryan
Geotripper
Silver Fox
Short Geologist
A Life-Long Scholar
Lockwood

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Thrust reactivation

Tue, 11 Nov 2008 09:42:28 -0500

It will come as quite a surprise to most of you to hear that this is my last day in South Africa. A couple of months ago, I was offered a Marie Curie post-doc at the University of Edinburgh, and tonight I'm boarding a plane back to the UK - this time to stay. Well, for a couple of years at least.

To be honest, I don't think it's sunk in yet that I'm leaving. Once my head has got round it all, I'll probably be in a mood more conducive to telling you about my new research, the wheres and whyfores of my move, and some reflections on what I have got, personally and professionally, from my two years in South Africa.

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Capetonian Geology: the Seapoint contact

Mon, 10 Nov 2008 07:28:59 -0500

In a previous installment, my intrepid wander along the Capetonian seafront ended at Seapoint, where slightly metamorphosed sediments of the Malmesbury group come into contact with the intrusive Cape Granite. In the photo I showed you then, the contact appeared to be fairly sharp.

However, if you look closely at the foreground of the photo above, you can see lenses of much darker material within the pale granite. These are actually bits of the Malmesbury Group sediments, completely surrounded, and incorporated within, the granite. The contact at Seapoint is actually anything but sharp; instead, over a hundred metres or so of the shoreline you can walk across a beautifully exposed example of a gradational contact. Starting on obvious outcrops of the Malmesbury group and heading east, first you see distinct veins of granite being intruded into the sediments:

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Geopuzzle #16

Fri, 07 Nov 2008 07:36:29 -0500

This weeks challenge comes via fellow Scibling Martin of Aardvarchaeology:

I've noticed something funny about the map of North America. The Great Lakes in the US form the end of a straight line of huge lakes extending north-west across Canada. Could you please tell me how that line of lakes formed?

It looks like he has a point:

Now, this is one of those situations where I can make an educated guess about the answer, but I'm neither sure if it's right or if I'm grasping the full story. If I'm even approaching a clue, this (right click to download) or this may prove helpful. Or not. Either way, get guessing.

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The US election in just three words

Wed, 05 Nov 2008 05:01:47 -0500

Good call, America.

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More Capetonian geology

Tue, 04 Nov 2008 12:22:38 -0500

Before continuing from yesterday the account of my journey along the Capetonian seaside, I should probably adhere to the principle that good field geology starts with knowing where you are, and where you're going. So, here's a Google Earth view showing my southward route along the Atlantic coast to the west of the city centre, between Three Anchor Bay and Seapoint.

As I approached Seapoint, it was clear that I had also about to cross a contact between two rock units: looking ahead along the coast the clearly bedded and ridge-like outcrops of the Malmesbury Group were giving way to much more rounded outcrops of a massive looking, lighter coloured, lithology.

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OpenLab 2008: more geobloggery needed. Much more

Tue, 04 Nov 2008 07:06:21 -0500

Time is running out to submit entries for the next edition of the Open Laboratory blogging anthology, and running down Bora's latest list of posts submitted so far reveals very few geologically-themed ones. In fact, I could find but two: this post from Callan, and one from the SVPOW guys. Only two? This needs to be rectified.

In 2007's anthology, Kim and myself were the sole representatives of the geoblogosphere. This time, it would be nice to mirror the explosive growth of our community in the past year with lots more geoblogging present, both in the list of nominations and in the final anthology. If we all submit something of our own that we're particularly proud of, and/or nominate one or two of our favourite posts from our fellows, then the first objective will be achieved. Then we'll just have to remind the judges that most of us have big pointy hammers. Not that we're trying to imply anything by that, of course...

As for myself, I'm thinking of possibly submitting this, or this, or perhaps even this. Or... Suggestions would be welcomed. In the meantime, I'm also going to be sure to take some time to find and submit some of the finer work of my infinitely more talented geoblogospheric colleages. Get to it, before someone starts thinking that biology and physics are better or something.

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Cape Town geology: less freaky than the rest of South Africa

Mon, 03 Nov 2008 10:59:24 -0500

Last week was my first visit to Cape Town, a place about which I had heard much, both before and after I moved to South Africa. A lot of this talk revolved about how different the Cape is from the rest of the country. I'll agree that, as a city, it did seem a bit more relaxed than Johannesburg; I certainly liked the fact that the city centre felt a bit more accessible. However, I can't really say I got that "more European" vibe that some had told me about. Still, there was one thing that made me feel a bit more at home: old rocks actually look old:

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AAPG Day 3: poster session outcast

Fri, 31 Oct 2008 10:46:34 -0500

Spot the odd one out, and meet me below the fold:

Tilt-Depth Method: A Simple Depth Estimation Method using First Order Magnetic Derivatives.

The Use of Multi-Level Potential Field Data in Regional, Geophysical Modelling

Satellite Gravity and Geoid Studies Reveal the Formations Underlying Large-Scale Basin Structures

3D Gravity Modeling in Deepwater Gulf of Mexico

Mapping and Delineating Prospective Geology with FTG Gravity Data

Integrated Seismic Structure, Stratigraphy & Magnetic Basement Interpretation: Offshore Louisiana Shelf

Gabon Regional Structural Framework, Derived from Gravity

A Palaeomagnetic Investigation of the Neoarchean Pongola Supergroup, South Africa

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AAPG Day 2: showdown at the Lusi corral

Thu, 30 Oct 2008 08:42:38 -0500

The afternoon of my second day at AAPG was spent at the session debating the origins of the Lusi mud volcano, which has been the subject of a number of blog posts around these parts. The selling point was that this would be the first time that the major proponents for the theory that the eruption was caused by a blow-out in the gas well being drilled nearby, and the competing theory that it was a response to a large regional earthquake that occurred two days before the eruption, had been collected in the same room to argue things out. Whilst this wasn't entirely true - there was a similar debate in London last week - I was quite happy to catch the rematch.

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Straw poll: poster or talk?

Wed, 29 Oct 2008 10:45:52 -0500

At the moment this post appears, I'll be standing in a poster booth desperately hoping that at least some petroleum geologists have (a) stuck it out to the bitter end of the conference, and (b) can feign an interest in Archean paleomagnetism. In the meantime, I'd like to hear your thoughts on the following question:

If you were given the choice, would you prefer your conference presentation to be a poster or a talk?

I'd be interested to hear the reasons for your answer, and what level of the academic ladder (post-grad, post-doc, junior/senior faculty) you're currently at.

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AAPG Day 2: industrial seismologists get all the cool toys.

Tue, 28 Oct 2008 16:41:10 -0500

It shouldn't come as much of a surprise that the industrial sector is out in force at AAPG; most of the main exhibition hall is taken up by exploration companies and consultancies showing off their technical and intellectual wares. And some of the stuff on display is enough to cause anyone's inner geek to explode in paroxysms of techno-joy.

The coolest thing that I've seen so far was an entire wall of linked monitors, which could be used to display 3D seismic data sets in stunning detail. Even better, it was interactive: lasers scanning in front of the display could locate a reflective pointer placed anywhere on the screen, movements of which could be used to rotate or zoom in or out of the dataset, or even to trace reflective horizons on-the-fly.

The guy giving the demonstration also showed me and Jeanette how you could use image processing routines to pick out fault planes, or even different packages of rock - such as channels - with specific acoustic characteristics, within a particular 3D volume. The level of discrimination they are now achieving with these processing tools is pretty incredible- it's a long way from picking out horizons with a colouring pencil - or even a mouse.

Anyway I was pretty much drooling, and I don't even do seismic interpretation. It makes me wonder - how many geologists went into industry not for the money, but for all the wonderful toys you get to play with?

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AAPG Day 1: rifting models, snowballs, and other miscellany

Mon, 27 Oct 2008 18:24:02 -0500

It has to be said that it's never been a particular ambition of mine to mix with the luminaries of the American Association of Petroleum Geologists. Still, lots of interesting research does get done in the name of finding and extracting oil: if you want to know where it is, and how much there is, and the best way to get it out of the ground, you need to understand the depositional systems that generate source and reservoir rocks, and how the tectonic development of particular regions has generated hydrocarbons and the structural nooks and crannies that allow them to accumulate. And sometimes, getting to grips with these questions forces you to look at some quite fundamental aspects of Earth Sciences.

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Trees growing on (or in) old rocks

Sun, 26 Oct 2008 10:36:24 -0500

The latest meme to hit the geoblogosphere involves trees, of all things. Of course, vegetation changes can give important clues to changes in the underlying rock type (the acidity, mineral content and texture of soils will change significantly if you go from a shale to a granite, for example, and so will the sorts of things that like growing in it). But sometimes, they take a more active geological role. This fig tree is growing roots into the rock (2.5 billion year-old limestone, in this case), and breaking it apart:

(why is the close-up is in black-and-white? I was obviously feeling arty that day)

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To Cape Town!

Fri, 24 Oct 2008 07:02:47 -0500

Right, I'm off to Cape Town for an action-packed few days. First, Christie has persuaded me to give a talk at her home University, hopefully followed by a beer or seven - after being beaten over the head with paleomagnetic terminology, my audience will almost certainly need it.

Over the weekend, I'll have the chance to do some sightseeing, which will hopefully include a view from Table Mountain, although the weather might scupper that. Then, from Monday to Wednesday, I'm attending the AAPG International Conference. By a convoluted route I've ended up with a poster to present in Wednesday afternoon's 'Advances in Gravity and Magnetics' session. There's a few other interesting-looking sessions in between, including a session devoted to everyone's favorite mud volcano, where the "man-made" and "earthquake triggered" camps will face off against each other and turn the air mildly turquiose with cutting remarks. And, since it's a while since I gave you the latest satellite image, here it is:

Depending on the state of internet access, I might try some conference live-blogging. No promises, though.

As an added bonus, Jeanette from Ten Million Years of Solitude is also in town, so it looks like a small geoblogger meet-up is also on the cards. If any other readers happen to be in town, let me know.

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