18 March 2014

On ignorance, bias, data, and the tentative nature of (scientific) interpretations

Posted by Callan

Yesterday’s post on the angle of repose in shale scraps falling off the “Wallbridge Unconformity” (?) outcrop I visited with Alan Pitts concludes the series of blog posts about new observations made along Corridor H. Several people wrote to me or commented on the blog posts how much they enjoyed reading the “virtual exploration” of these new sites. Apparently I also have a reader at the Institute for Creation Research (ICR). This young-Earth creationist group is not merely anti-biological evolution; They also advocate for “Flood geology,” the idea that the world’s geologic strata were laid down in the Noachian flood of the Bible. I’m grateful to Peter L., who keeps an eye on the young-Earth creationists at the ICR at his blog Eye on the ICR, for alerting me to a creationist critique of my blog post a few weeks back on the possibility of a marine incursion into the red beds of the Hampshire Formation.

So – it appears we are not done with Corridor H yet. Let’s review the story, and seek what lessons we may from the creationist’s critique.

As you may recall, in exploring the new roadcuts along Corridor H, Alan Pitts and I were surprised to see a unequivocally marine layer sandwiched between red beds. We had tentatively identified the red beds (oxidized river + floodplain deposits) as Hampshire Formation, but the Hampshire Formation was supposed to be terrestrial only (there are no rivers and no floodplains below sea level in fluvial-estuarine-marine connected depositional systems). The marine incursion began sharply, and was 5 meters thick. Here’s the base of it:

IMG_1818anno

This observation left us with a conundrum of interpretation: As I said then,

We interpret the black layer as resulting from low-oxygen marine deposition. But that doesn’t sound like the Hampshire Formation. Two possibilities occur to me: Does this suddenly black limy interval indicate that this isn’t the Hampshire Formation? Or did we just ‘discover’ a new marine portion of a previously-thought-to-be-terrestrial-only geologic unit?

These questions are hypotheses – possible explanations for the novel observation. Geologists are comfortable with several possible explanations swimming around in their head at once. We don’t just pick one. We work with all of them, and attempt to pare them down to the least possible number by seeking additional evidence (data) to confirm one or rule out another. As an indication of the process of thinking about geology, I posted my photos here on this blog along with my list of two possible interpretations, and then eagerly awaited feedback from my readers, many of whom know more about sedimentary rocks and sequence stratigraphy than I do. Though I was confident in my observations, I wasn’t sure what I was missing that would allow this sequence to make sense. So I put my preliminary data out there and asked “What do you think?”

Sure enough, I soon got some great feedback. Let’s go ahead and file it under “peer review.”

To start with, the fossils I photographed were partly useless (snails, which can be freshwater or marine), and partly diagnostic (articulate brachiopods).

IMG_1808

Several of my readers, including Howard Allen and Mike Huggins, noted that this appears to be a productid brachiopod, which is an index fossil for the late Paleozoic. Howard noted it was a ‘dead ringer’ for a species which indicates Mississippian aged sedimentary deposits in Alberta.

So there’s one line of evidence to suggest that hypothesis A (“these strata aren’t Hampshire Formation”) was correct.

Mike Huggins also pointed me to a reference that suggested there are in fact brackish/estuarine strata within the Hampshire (evidence consistent with Hypothesis B).

Then there is the location: this stretch of Corridor H climbs the Alleghany escarpment, the lip of the Appalachian Plateaus province. The strata there are younger than what I’m used to seeing the Valley & Ridge province. Though we didn’t have a good geologic map with us during the field trip, if I use the online geologic map of West Virginia, it suggests an upper Mississippian age for these beds, though it’s hard to pin down the exact location because the road is so new it’s not on Google Earth. The outcrop in question was a few hundred feet below the lip of the plateau (lined with the wind turbines you can see in some of the post’s photos. So my simplistic “redbeds=Devonian” initial interpretation is likely invalidated by this non-Valley-&-Ridge position. That’s Mike Huggins’ interpretation, too.

A USGS sedimentary geologist and mapper whom I consulted concurs with that assessment. He got to briefly ogle the beds on a trip out to Canaan Valley the weekend before the blog post was published, and wrote (in an email) to me that he thought they were, “upper Mississippian Mauch Chunk Group or lower Pennsylvanian Pottsville Group.”

I’m very grateful to these three geoscientists for offering me their feedback. Based on their “peer review,” I think the situation was this: I was simply ignorant of the wealth of strata that feature red beds in our area. I was projecting the bias of my own limited experience onto rocks which were outside my experience. Based on the arguments my colleagues made in response, I now think these strata are likely of Carboniferous age, rather than Devonian. The strata aren’t the Hampshire, but are instead more recent, probably Pottsville Group. And thus my conundrum dissolves like smoke in a breeze of fresh understanding. With this more refined version of Hypothesis A in my head, I’m now eager to return to the roadcuts and evaluate them anew. I’ll form new interpretations (perhaps several, perhaps competing, all subject to denial) and seek new data.

The point of this blog post is to emphasize that my conclusions were (a) tentative, and (b) subject to dismissal based on new evidence. I was ignorant of key facts, and limited by my lack of experience. New evidence was presented, and that evidence changed my mind about my hypothesis. In other words, the conclusion is tentative, and must hew to the data.

I would encourage my readers to consider what evidence Tim Clarey, author of the ICR blog post, would find to be inconsistent with his hypothesis. Can any data (fossil content, sediment type, location on Earth’s surface) convince a Flood ‘geologist’ that the global flood hypothesis is incorrect?

Clarey writes,

Something is definitely wrong with the uniformitarian story—why else would scientists be so surprised by the black rock and marine fossils? Could it be that all these strata—the red and black rocks—are deposits from the great Flood? This interpretation eliminates the mystery of how marine fossils are found sandwiched in between red sands and shale. It also solves the mystery of the black, organic-rich shale.

Rapid deposition during the Flood would have preserved ample organic material to give a black coloration to the rocks. There is no need to call on special, restricted, low-oxygen conditions to explain the dark color. Organic debris was merely buried within the Flood sediments along with the fossil shelled animals.

A Flood origin for the sediments accounts for the rock types we observe much better than secular models. Creationists don’t have to fabricate tales of the sea level rising and then draining off the land suddenly, over and over. We just recognize it happened once, in a catastrophic way, about 4,500 years ago.

Clarey wants it both ways – the black is marine (and therefore indicative of not just any marine transgression, but a specific global flood of divine origin, inexplicable by a modern understanding of physics and Earth processes). But not only the black indicates Noah’s flood, according to Clarey, but does the red. I guess it follows that any sandstone you’d care to reference is from the Flood, and so is all the world’s conglomerate, and so is the limestone, including ooids and mudcracked strata, and so is the diamictite, and so is the shale full of plant fossils, and — what the hell — so is the granite and the schist and the basalt. Clarey holds a PhD in geology from Western Michigan University. You know they can’t be too psyched about that, when all his observations lead to the same conclusion. There’s only one conclusion to a young Earth creationist, and no data can ever dissuade him or her.

4,500 years ago, there were bristlecone pine trees growing in the White Mountains of eastern California. One wonders how Clarey reconciles that fact (a matter of counting tree rings) with his silly idea that the whole planet was under seawater.

I am amazed anew by the young-Earth perspective. It is a blinkered, resolute, evidence-free piece of sacrosanct silliness immune to any rational line of argument.