Monday, December 12, 2011

Privilege, Equality, and Disparity: A Link To A Totally Rad Essay

I just wanted to quickly point out a really excellent essay that does a killer job deconstructing and exploring the (sometimes stealthy) role that "privilege" has in creating disparities between folks.  The essay, titled "Sacrificing Privilege" and hosted at Skepchick, is a clear and well-written exploration of how a "privileged" status, defined on the basis of race, gender, or what-have-you, can serve as the basis of a pervasive and potentially "invisible" culture of bias. 

This is an extremely important message that we in the sciences (and especially the Earth Sciences) NEED to understand if we ever want to get away from the "(White) Boys' Club" that defines so many fields.  As discussed here in a previous post, Geology has a real problem with regards to gender; understanding and working to eliminate the (often hidden) cultural biases that make it hard for women and minorities to find a home in the sciences is the only way that we'll ever get better.  So everyone read the essay linked above!  It's long, but well worth the time!

Tuesday, December 6, 2011

Evaporite Casts in Sandstone

I've been working, as part of the ol' PhD rigamarole, in the Wilkins Peak Member, which is part of the Eocene Green River Formation in southwest Wyoming.  Anyway, this part of the world during the Eocene was characterized by extremely high evaporation coupled with relatively low precipitation, which is a perfect setting for the formation of evaporites!  High evaporation rates drive off water, while leaving behind water soluable ions, resulting over time in highly concentrated brines from which evaporite minerals form. 

In previous posts, I've shown some modern examples of evaporite formation from Death Valley, where evaporites are precipitating on a playa surface, which is a pretty good analogue for parts of the Wilkins Peak.  This previous post actually shows some evaporite mineral casts from the purely lacustrine portion of the Wilkins Peak, probably some sort of Na-rich evaporite.

However, you don't have to be in the lake for evaporites to form!  These pictures below are evaporite mineral casts preserved in sandstones that formed as part of the floodplain/overbank setting of a fluvial system that fed into the lake. 

Here's a closer view, showing the bladed, fairly delicate looking crystalline features of the evaporites, preserved in the sands. 

I reckon these are Nahcolite casts, on account of their elongated crystal habit, but then again I'm no evaporite specialist.  Still, they're kind of nifty!

Friday, December 2, 2011

Ophiomorpha in core

Trace fossils are, as I've said before, pretty rad.  As a sed/strat type, I mostly appreciate them for their utility in paleoenvironmental reconstructions, their ability to help us constrain substrate conditions, and the help they can give us in interrogating rates and processes of sedimentation.  And, of course, there's all sorts of biological and ecological info to be gleaned from the paleoichnological record as well.

Trace fossils are particularly valuable when all you've got is 3 inch-wide cores to work with!  I'm mostly a field guy, but sadly, some strata remain inaccessibly trapped below the surface of the earth, removed from the joyous and perfect cycle of erosion and redeposition that is the true destiny of all rocks everywhere.  When we want to investigate these strata, we're forced to yank a plug of rock out of a well somewhere, and just hope for the best.  It's not ideal, but you gotta work with what you've got...

Anyway, below are a few pictures of some Ophiomorpha traces I found in core from the Paleocene-Eocene Wilcox fluvial/alluvial/deltaic sediments of the Gulf Coast.  Ophiomorpha is such a neat little trace fossil; a little shrimpy bastard digs his way into some shifting sediment, and in order to keep his little dwelling tunnel safe from collapse, he rolls his own shit into little balls, and sticks it into the walls of the burrow.  Ah, The Grandeur of Nature at Work!

In the picture above, we've got a pretty nice cross-section in a massive, medium-grained sandstone.  You can see pretty clearly the nice fecal ball lining surrounding the inner (and, in the animal's lifetime, what would have been hollow) chamber.

Here's a cut along the length of an Ophiomorpha, truncated by an erosion surface and subsequent plow-and-fill sediment, which was itself burrowed into by yet more Ophiomorpha-producin' shrimp.

And, finally, here's an oblique cross-section of another little tube (maybe a bit squashed, as well?).  Trace fossils are handy things to have around, especially when all you've got is core!

Thursday, December 1, 2011

Burgess Fauna Zapruder Film

Here's something to start the day off RIGHT!  A little movie, from the Royal Ontario Museum, showing a catastrophic mud-rich turbidity current sweeping over some poor Burgess Critters!  They've even got the ol' cinematic rumble going on!  Poor little Anomalocaris!