Farrar Pond lies in a part of Lincoln that—unlike most of New England—is nearly devoid of visible rocks. (Colonial-era irony: the Massachusetts farmer exhausts his life prying boulders out of his fields, hauling them aside, and grunting them up into neat stone walls. So when he dies, they plant him with a rock on his head.) Even where exposed ledge doesn’t mock attempts to garden or farm, stones—through a combination of ice-lifting and erosion—continually grow right out of the ground.
But not so much around here, because there aren’t a lot of rocks in the underfoot mix. As per the various surface-geology and soils maps shown or referenced on the Geography page and parodied in this post, the land around Farrar Pond comprises lake- or river-bottom (“glaciolacustrine” and “glaciofluvial”) deposits of material scraped and milled from regions further north, now graded into valuable bank gravel and sand, weathered above and bio-degraded these past ten millennia or so into excellent light loams. Great for septic systems—hence at risk from illegal mining-type exploitation—and easily amended with leaf debris or wood chips into superb garden soil. For anyone interested in characteristic local glacial landforms (esker, drumlin, kettle, kame, delta, etc.), the work of great naturalist (and former Lincoln science teacher) Neil Jorgensen is highly recommended.
And yet naturally arrived rocks do turn up here on occasion, usually small:pebbles to melon-sized, well rounded and smoothed by abrasion. Often, these are of a fine-grained pink granite, quite unlike larger glacial erratics or gray ledge exposed outside this high-perc zone. However did they get here?
One fine day a couple of years ago, a pleasant young man was seen wandering the small side-roads by the pond, peering around intently but with no obvious target. He appeared not at all lost, inquisitive but without the usual nature-watcher’s binoculars (or the burglar’s studied insouciance). Asked if he wanted assistance, he explained that he was a geology graduate student doing field work involving pink granite cobbles, and were any such to be found hereabouts? There were, and he promptly identified them as to type, formation and site of origin. He also provided several helpful references (some cited above), and agreed to share the results of his study. Degree now in hand, Dan Dabrowski is kindly providing a (relatively) lay-accessible summary of his findings, offered in the post to follow (above, in a normally configured browser) for our enjoyment and edification. For more serious readers, he has donated a copy of his actual thesis to the Lincoln Public Library.