Posted on November 26, 2013 by earth science society

I only ever truly loved two textbooks. I only ever loved these books because they were capable of captivating my attention, enhancing my understanding, and making me realize the depth of the subject. Most textbooks are poorly written encyclopedias that should be thrown out, no matter how beautiful they look and how famous their writers. No matter how relatively useful they are.

The first textbook I ever truly loved was ‘Sand and Sandstone’ by Francis Pettijohn, Paul Potter and Raymond Siever. It was first published in 1972 by Springer. I used a library copy during my MSc studies, wanted to own it right away, but couldn’t afford it until I was a professional with a real salary. I bought it in 1984. The second edition was published in 1987 and you can still buy it for $239.00 (ex shipping). YES! I am obviously not the only one: this must be a darn good book if Springer can still sell it for that price 26 years after it was published!

What was it about this book? Opening it again after many years, I can’t really find a specific page to bring me back to that feeling of excitement. Maybe it was its inviting language: on page 7 the young student reads: ‘just where is sand in the world today…?’ Or maybe it was because the book was actually the result of a workshop and therefore reads as a workshop discussion, something I wasn’t really exposed to as a student in the Netherlands. For example, on p. 107 we read “Truly massive beds of sand appear to be very rare which is indeed fortunate, for if they were common, we would be hard pressed to explain them”, showing that the writers aren’t all-knowing wizards, they are real human beings with questions.

But they were confident researchers! The paragraph on Sandstone Petrogenesis has the following subsections: The Question, The Hypotheses, The Evidence, The Verdict. The Question is whether Climate, Tectonics, Provenance or Depositional Environment is the most important influence on the petrographic character of a sandstone. The Verdict: Tectonics – a textbook with sections written as a whodunnit, terrific.

Maybe I was simply excited about this book because I was from the Netherlands, a country with next to no rock outcrops, consisting largely of sand, mud and peat and locally a lot of glacial erratics (certainly in my home town, because I grew up on a moraine) – and here was something that made all that home grown dirt a Science!

Of the three authors of Sand and Sandstone, I only ever met Paul Potter once when he gave a talk about his research on the tectonic signature of the beach sands of South America. He published a lot on that topic – extremely elegant papers mostly in the rather obscure ‘Journal of Geology’.

Those articles on the modern sands of South America are true gems. I have routinely used the three referenced below here when teaching sedimentology. Paul Potter asked a simple question: “how can we reconstruct ancient continents on the basis of sandstone petrology”? Obviously: by studying a modern continent, one that is properly situated and nicely varied (geologically speaking). Collect a few hundred samples (he calls it his ’18 year hobby project), process and analyze them in the same consistent manner – and plot the results:

Potter, 1986, Fig. 10

The beach sands of the Pacific province reflect an active continental margin, dominated by volcanic rock fragments (L).

The Brazil province reflects an eroded shield and the Amazon Basin, a typical passive continental margin – most of the quartz is monocrystalline.

The Caribbean is split in a western and eastern province. The western province has mostly volcanic lithics, whereas the eastern province has a Q/F/L of 69/8/23 and the lithics are more metamorphic lithics

Argentina has a misleading signature, suggesting an active margin, but this is of course a passive margin. The signature is explained by the fact that Patagonia is narrow and the climate dry.

There is a wonderful interview with Paul Potter on http://www.minutegeology.com – I have no idea who put that site together, but it’s worth checking out – nothing but interviews with highly respected earth scientists. Paul is very modest about his own accomplishments, giving mostly credit to his colleagues and characterizing himself as “someone who happens to be fairly good at finding a rose in a field of weeds”, a statement that implicitly refers to Kuhn’s “Structure of Scientific Revolutions”. Kuhn defined most scientific practice as ‘ordinary mopping up’. Paul Potter says that “ordinary science is nuts and bolts”, that “someone sometimes has an idea” (that sticks out) and defines the concept of Sequence Stratigraphy as such an idea. I think that “being able to find a rose in a field of weeds” is also proof of being in the business of generating ideas. Deciphering the tectonics of a whole continent on the basis of a few hundred beach samples is definitely an original idea.

References

http://www.minigeology.com

Pettijohn, F. J., P.E. Potter and R. Siever, 1987, Sand and Sandstone. Springer Verlag, 618 p.

Potter, P.E., 1983, South America and a few grains of Sand. Part I: Beach Sands. The Journal of Geology, v. 94, no. 3, p. 301-319

Potter, P.E., 1984, South American modern beach sand and plate tectonics. Nature, v. 311, p. 645-649