Sunday sand: where's Walter?

Not long ago, my old friend (in every sense), Walter, set down in front of me a wonderful and equally venerable Dutch tobacco tin. This he had retrieved from a far-flung and dusty corner of his remarkable forge in the rolling hills of Pennsylvania – I can vouch for the fact that, given the complexity and number of such dusty corners, his locating it attests to the fine state of his memory.

He opened the can with care and relish and revealed the contents: a mystery sand from an Oregon beach. It seems that the fine state of his memory only extended so far: he could not recall where he was when he collected it (it was, after all, the 1960s). The beach was purple-grey-green, iridescent in the sunlight, and the sand an interesting pot pourri of local ingredients. It’s so poorly sorted that the larger grains don’t qualify as sand at all, being more towards the gravel family (the left image is simply a desk-top photo). This, together with the angularity of many of the grains, suggested to me that this is a river sand, but Walter insists that he was on a beach – somewhere in Oregon.

 
Now there are parts of the Oregon coast that are renowned for black and grey sand beaches – indeed, the inappropriately named Gold Beach is one (shown here). These beaches are along the southern coast of the state, and the ingredients derive from the typically complex geology of the interior, particularly that of the the Klamath Mountains. The geology records the same kind of tectonic mayhem that is found all down the west coast of North America, and similar to that of the San Francisco area, one of whose sands I’ve described before. But up in Oregon, there’s a further complication, and added ingredient – the volcanoes of the Cascade Range. Another analogy with the geology further south is the mining history of Oregon: placer sands yielding, amongst other treasures, gold and platinum – hence, perhaps, the name of Gold Beach. The mining activity took place along the major rivers draining the mineral-rich terrains of the interior – the Coos, the Coquille, the Rogue. These rivers brought their cargoes of sand down to the coast where waves and storms continued the winnowing and sorting, and concentrated placer deposits of minerals have also been (and in places still are) mined along the beaches and old coastal terraces. The geological map of southwest Oregon (thanks to Andrew Alden and his online collection) shows the diversity of ingredients delivered to the coast: in red and pinks, the young volcanics of the Cascades, in yellows and greens the sedimentary and volcanic rocks of old collisional terrains (together with patches of granites in red), in purple fragments of oceanic crust and mantle caught up in the turmoil, and in brown around Coos Bay, the detritus of all this chaos.  

So it seems to me that Walter’s sand probably comes from that stretch of coast south of Coos Bay, where the beaches are dark and the rivers supply endless loads of poorly sorted sediments for the coastal processes to play with. Any other ideas in this game of “Where’s Walter”?

[For those interested in the black sands of Oregon and details of the state's placer mining history, here are some further links: the Oregon History Project, Netarts Bay, a 1903 article on Rogue River platinum, beach mining history in California and Oregon, and a couple of articles from The Ore Bin, a publication of Oregon's Department of Geology and Mineral Industries - one here (see page45) and the other here (see page 21).]

Comments

[Walter]

Dear sir;

While you are correct that I am öld, I must remind you that you are ölder.

[Sandglass]

Dear Walter,

"You are old, Father William," the young man said,
"And your hair has become very white;
And yet you incessantly stand on your head—
Do you think, at your age, it is right?"

"In my youth," Father William replied to his son,
"I feared it might injure the brain;
But now that I'm perfectly sure I have none,
Why, I do it again and again."