Monday, March 16, 2009

Keeping Track of Samples During Field Work

Rummaging through drawers this Sunday I came across some old field photos. I did very focussed sampling of outcrops during my Ph.D. research on mid-late Ordovician carbonates. This was because I was interested in finding out how far below the preserved cycle top does meteoric diagenesis penetrate. How thick were the meteoric lenses that developed during sea-level falls? This was linked to bigger questions like climate change induced sea-level fluctuations, the changes in amplitude in sea-level if any from a mid-Ordovician greenhouse to a late Ordovician icehouse, and the control of basin geometry and stratigraphic architecture on movement of fluids. But the first step was to generate the basic data and sample the outcrop at about 4-6 inch intervals.

That meant I had to keep an accurate record of where exactly on the outcrop any particular sample came from. I was going to just sketch the outcrop was best as I could, but my adviser suggested I borrow his Polaroid camera. That worked out quite well. I could take a picture, put the photo print in my pocket for a few minutes to develop the image and annotate on it. I have some images below of annotated outcrops. These don't show completed annotation. For example they don't have sample numbers placed besides the dots. Eventually, I ended up with a consistent numbering scheme. Cycles present in the outcrop were numbered from bottom to top in ascending order and the samples within each cycle were numbered from bottom to top in ascending order.

I sketched the outcrop too. I found it useful to just slow down my work flow, sit in front of the outcrop and draw. I wasn't too interested in analysis of sedimentary structures, but it helped me think of basin stratigraphy and the cycle stacking patterns in front of me. And I took photos from a regular camera, my trusty Minolta 700 (my research as you might have guessed was in the pre-digital camera epoch). I used one of those dual purpose films. That meant I could develop slides for presentations and regular prints to slap onto my thesis from the same film. Those I sent to a lab in Seattle to develop. Overall this three pronged approach to representing the outcrop and tracking samples worked out quite good.

Any of you geobloggers use a Polaroid camera? If you are doing very focussed sampling, how do you mark the location of your sample? Sketching is one way to go about it, but is there a combination of a digital camera and a field laptop that might be used productively and efficiently? Aerial photos or high res satellite image might work if your sampling intervals are wider apart and the outcrop is illuminated and is not a vertical cut. Any other method?

My Polaroid became quite well know to the state troopers patrolling Interstate 59, Interstate 75 and the many state and county routes in northern Alabama, Georgia and southern Tennessee. I guess I was a strange sight standing along road cuts with my two cameras, a sledgehammer and a row of labeled zip lock bags with my samples in them. The police used to pull up and politely ask me what I was doing. I used to launch into a lecture on diagenesis but with a nod they would leave. I guess they weren't interested in geology, but they were kind enough never to interfere with my work.


  1. On of our state surveys recently made the leap to linked PDA's-digicams-GPS's. Evidently it rocks.

  2. I was just going to ask about that, Chuck... Anyone actually used such a digital setup for annotation on the scene?

  3. Is this combo slow to catch on in geology? Callan, what's your experience with Virginia geology community and the state survey? GPS-PDA's for quite a while have being used for GIS stuff and adding a digicam to it makes sense for outcrop geology annotations.

  4. I used to take quite a lot of Polaroid photos in the field, then draw on them and annotate while in the field looking at the outcrop. I haven't really thought about it for a number of years.

    I think it could still be useful in these digital days. Take good digital photos along with a Polaroid, mark the things you need on the Polaroid - samples, structures or contacts - then transfer the info to the digital image back in the office or motel.

    At least, I don't currently have access to something that would take excellent digital photos, with GPS, with annotation capabilites all at the same time.

  5. Silver Fox- You workflow seems efficient. Yes I would think that annotating by hand in the field on a Polaroid print seems just more easier than using a PDA and marking on the screen.

    But others who have used the digiCam PDA combination may have a different experience!