Geo 888: Stranded Terrace Deposits

Overlooking a small cove just north south of Sunset Bay, one can fairly easily spot the buff-colored layer of semi-consolidated sand, about six feet thick, overlying the tilted Eocene beds of the Coaledo Formation. It's a beautiful spot, and a nostalgic one for me. When I was young and hale, I clambered down into this cove a few times; there are some gorgeous sedimentary structures in the strata here. But at this point, with poorer balance and limited endurance, there's no way I'll be down there again unless a decent path is constructed. I have no reason to think that has been, or will be, done. The routes down were precarious, with tree roots and vines, mostly, as the only hand-holds, and the climbs back up were often scary, or worse if I had taken samples (one ten-pound block, in particular, comes to mind).

There's a modest fault running through the cove; this is particularly apparent in the ZoomEarth satellite image. I'm pretty sure the sandstone bed running from the middle toward the lower right is the same as the one on top of the tilted slab on the middle left.

However, the feature the sprang out at me on this trip was the isolated bit of terrace material on top of the anvil to the far right. There a tension between subsidence and uplift in this area. On a scale of millennia, there can be subsidence, as demonstrated by the dead tree stumps on the inner south shore of Sunset Bay. On a longer scale, tens of thousands to millions of years, terraces like this (and six more higher up tentatively identified) clearly show a pattern of tectonic uplift. That little pile of stranded terrace deposits will soon fall as the latest victim to the ongoing ups-and-downs of this area's coastal elevator.

Photo unmodified. July 21, 2016. ZoomEarth location.