-
breaking up in the Cryogenian. This
period includes the
formation of the
Keweenawan Rift at
about 1100 Mya.
Fossils of the
oldest known ****ually reproducing...
- The
Midcontinent Rift
System (MRS) or
Keweenawan Rift is a 2,000 km (1,200 mi) long
geological rift in the
center of the
North American continent and south-central...
- The
Keweenawan Supergroup is a
supergroup of
volcanic and
sedimentary rocks that fill the
Midcontinent Rift
System in the U.S.
states of Michigan, Wisconsin...
- (Sverdrup Basin)
Iceland Karoo-Ferrar
Kerguelen (Broken Ridge)
Marathon Keweenawan Long
Range Mackenzie (Coppermine
River Mackenzie **** swarm) Matachewan...
- only 21 feet (6.4 m)
below the lake's surface. The
shoal is a hump of
Keweenawan basaltic lava
flows with
ophitic interiors and
amygdaloidal tops in an...
- area of the rift. The rock
sequences thereby created are
known as the
Keweenawan Supergroup.
Rocks of this
group north of Lake
Superior are the layers...
- 2018-06-08. Huber, N. King (1973). "The
Portage Lake
Volcanics (Middle
Keweenawan) on Isle Royale, Michigan".
Geological Survey Professional Paper. Professional...
-
devoid of fossils, its age is
difficult to ascertain,
though it may be of
Keweenawan Age (about 1100 Mya). The
group is
composed of conglomerate, sandstone...
- sandstones, conglomerates, ash beds, and
flood basalts ****ociated with the
Keweenawan Rift. The
native copper deposits originate in fissures,
steeply dipping...
-
Geological map of
North America showing (in beige) the
Midcontinent Rift, here
labelled Keweenawan Rift....
