The Jacobsville Sandstone (= “Eastern Sandstone” in early geologic literature) is a mottled reddish-pinkish-whitish, fluvial (river system) sandstone that outcrops in many areas of Michigan's UP, especially in the Keweenaw Peninsula, Marquette, and Munising areas.  It dates to the late Mesoproterozoic (~1.03-1.07 billion years).  The Jacobsville principally varies in lithology from nearly pure quartzose sandstone to arkosic sandstone.  Granules, small pebbles, and rip-up clasts may be seen in some outcrops.



The two photos below show nicely cross-bedded Jacobsville Sandstone outcrops at Miner's Beach, at the mouth of Miner's River, Pictured Rocks National Lakeshore, east of Munising (see map).  The Jacobsville at Miner's Beach consists of light pinkish-gray quartzose sandstones that are moderately well-sorted, with subangular to subrounded, medium-grained quartz sand.  Some of the quartz grains are slightly pinkish.


Jacobsville Sandstone (above & below) - cross-bedded quartzose sandstones from the ~uppermost Jacobsville Sandstone at Miner's Beach.

Jacobsville Sandstone



Here's a Jacobsville Ss. outcrop at Quincy Mill (see map), in Michigan's Keweenaw Peninsula, near the towns of Hancock and Houghton.  The Jacobsville here is a mottled pinkish-reddish, moderately sorted, fluvial arkosic sandstone.  Lenses of coarse-grained sand, granules, small pebbles, and reddish shale rip-up clasts are present in a few horizons.


Jacobsville Sandstone - outcrop just northeast of Quincy Mill, Keweenaw Peninsula, UP of Michigan, USA.  The rocks here are arkosic sandstones.


Jacobsville Sandstone (outcrop at Quincy Mill) with dark red rip-up clasts of shale.



Jacobsville Sandstone (5.6 cm across) from lakeshore outcrops along Marquette Bay, Lake Superior (see map).  This arkosic sandstone is rich in quartz and K-feldspar sand grains, plus a few scattered muscovite micas.  The sand is dominantly subangular and coarse-grained to very coarse-grained.



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