Proterozoic reactivation of the southern Superior Province and its role in the evolution of the Midcontinent rift

1997 ◽  
Vol 34 (4) ◽  
pp. 562-575 ◽  
Author(s):  
Matthew L. Manson ◽  
Henry C. Halls
Keyword(s):  
Lake Superior ◽  
Dyke Swarm ◽  
Superior Province ◽  
Midcontinent Rift ◽  
Potential Field Data ◽  
Major Activity ◽  
The North ◽  
Western Lake ◽  
Narrow Belt ◽  
Radiometric Data

Major reverse faults associated with the late compressional phase of the 1.1 Ga Midcontinent rift in the western Lake Superior region appear to cut across the rift at the eastern end of the lake and join with reverse faults on the eastern shoreline, defined on the basis of geological and potential field data. The continuation of the faults across eastern Lake Superior is inferred on evidence drawn from nearshore shipborne magnetic surveys together with new interpretations of published bathymetric and GLIMPCE aeromagnetic data. In the Archean Superior Province about 100 km east of Lake Superior, paleomagnetic and petrographic data from the 2.45 Ga Matachewan dyke swarm show that the Kapuskasing Zone, a narrow belt of uplifted crust, can be extended to within 50 km of the Lake Superior shoreline and has bounding reverse faults that are almost continuous with two faults of similar dip and sense of displacement that define the inversion of the Midcontinent rift in the central and western parts of the lake. Since the Kapuskasing Zone is dominantly a Paleoproterozoic (about 1.9 Ga) structure, the continuity suggests that the Lake Superior faults, whose last major activity was during the Grenville Orogen, may represent reactivation of much older faults that were part of an extended Kapuskasing structure. Within the Superior Province to the north and east of Lake Superior, published radiometric data on biotites suggest a series of alternating crustal blocks of varying tectonic stability, separated by northeast-trending faults. The Lake Superior segment of the Midcontinent rift developed within the most unstable block, bounded by the Gravel River fault to the northwest and the Ivanhoe Lake fault (the eastern margin of the Kapuskasing Zone) to the southeast.

Geochronology of the North American Midcontinent rift in western Lake Superior and implications for its geodynamic evolution

1997 ◽  
Vol 34 (4) ◽  
pp. 476-488 ◽  
Author(s):  
D. W. Davis ◽  
J. C. Green
Keyword(s):  
North American ◽  
Lake Superior ◽  
Flood Basalt ◽  
North American Plate ◽  
Rift System ◽  
Midcontinent Rift ◽  
Subsidence Rate ◽  
The North ◽  
Western Lake ◽  
Midcontinent Rift System

Volcanism in the Midcontinent rift system lasted between 1108 and 1086 Ma. Rates of flood-basalt eruption and subsidence in the western Lake Superior region appear to have been greatest at the beginning of recorded activity (estimated 5 km/Ma subsidence rate at 1108 Ma) and rapidly waned over a period of 1–3 Ma during a magnetically reversed period. The age of the paleomagnetic polarity reversal is now constrained to be between 1105 ± 2 and 1102 ± 2 Ma. A resurgence of intense volcanism began at 1100 ± 2 Ma in the North Shore Volcanic Group and lasted until 1097 ± 2 Ma. This group contains a ca. 7 Ma time gap between magnetically reversed and normal volcanic sequences. A similar disconformity appears to exist in the upper part of the Powder Mill Group. The average subsidence rate during this period was approximately 3.7 km/Ma. Latitude variations measured from paleomagnetism on dated sequences indicate that the North American plate was drifting at a minimum rate of 22 cm/year during the early history of the Midcontinent rift. An abrupt slowdown to approximately 8 cm/year occurred at ca. 1095 Ma. These data support a mantle-plume origin for Midcontinent rift volcanism, with the plume head attached to and drifting with the continental lithosphere. Resurgence of flood-basalt magmatism at 1100 Ma may have been caused by extension of the superheated lithosphere following continental collision within the Grenville Orogen to the east.

Post-Keweenawan compressional faults in the eastern Lake Superior region and their tectonic significance

1994 ◽  
Vol 31 (4) ◽  
pp. 640-651 ◽  
Author(s):  
Matthew L. Manson ◽  
Henry C. Halls
Keyword(s):  
Lake Superior ◽  
Volcanic Rocks ◽  
Eastern Region ◽  
Reverse Fault ◽  
Field Observations ◽  
Aeromagnetic Data ◽  
Midcontinent Rift ◽  
South Side ◽  
The North ◽  
Western Lake

GLIMPCE aeromagnetic data in eastern Lake Superior are characterized by a series of strong easterly- and northeasterly-oriented gradients that relate to mapped post-Keweenawan faults occurring along the eastern shore. The reversed nature of three of the faults is established through field observations and potential field modelling. Middle Keweenawan volcanic rocks at Mamainse Point are in fault contact on their south side with upper Keweenawan sandstone of Bayfield–Jacobsville type. Gravity modelling suggests that the fault is a low angle thrust dipping to the north. Field observations and high-resolution aeromagnetic data show that it extends inland along the southern margin of the Batchawana Greenstone Belt for at least 17 km. To the west, the Mamainse Point fault may extend across eastern Lake Superior to the Keweenaw Peninsula, linking several offsets in the seismic data that are consistent with the same attitude and sense of displacement. Along the south side of Batchawana Bay at Havilland, sandstones of Bayfield–Jacobsville type are isoclinally folded against a package of upthrust older rocks that include drag-folded middle Keweenawan volcanics. At Grindstone Point, north of Cape Gargantua, a reverse fault separating isoclinally-folded upper Keweenawan sandstones from Archean basement may, on aeromagnetic evidence, be an eastward extension of the Michipicoten Island fault.These faults mark a significant change in the style of late compressional tectonism observed within the Midcontinent Rift. All cut Keweenawan rocks across strike. The inference is that broad north–south or northwest–southeast compression, consistent in timing and orientation with the Grenville Orogeny, led to a reversal of movement along the major graben faults in western Lake Superior and was taken up in the eastern region by reverse faults oriented normal to the extensional axis of the rift.

The North American Midcontinent Rift beneath Lake Superior from Glimpce seismic reflection profiling

Tectonics ◽  
1989 ◽  
Vol 8 (2) ◽  
pp. 305-332 ◽  
Author(s):  
W. F. Cannon ◽  
Alan G. Green ◽  
D. R. Hutchinson ◽  
Myung Lee ◽  
Bernd Milkereit ◽  
...  
Keyword(s):  
North American ◽  
Seismic Reflection ◽  
Lake Superior ◽  
Midcontinent Rift ◽  
The North ◽  
Seismic Reflection Profiling

PRELIMINARY 3D MODEL OF THE MIDCONTINENT RIFT SYSTEM IN THE WESTERN LAKE SUPERIOR REGION, WISCONSIN, MINNESOTA, AND MICHIGAN

2016 ◽  
Author(s):  
V.J.S. Grauch ◽  
◽  
Michael H. Powers ◽  
Samuel Heller ◽  
Eric D. Anderson
Keyword(s):  
3D Model ◽  
Lake Superior ◽  
Rift System ◽  
Midcontinent Rift ◽  
Western Lake ◽  
Midcontinent Rift System

INTEGRATED GEOPHYSICAL MODELING PROVIDES INSIGHTS INTO THE THREE-DIMENSIONAL GEOMETRY OF THE MIDCONTINENT RIFT IN WESTERN LAKE SUPERIOR

2018 ◽  
Author(s):  
V.J.S. Grauch ◽  
◽  
Esther K. Stewart ◽  
Laurel G. Woodruff ◽  
Eric D. Anderson ◽  
...  
Keyword(s):  
Lake Superior ◽  
Three Dimensional ◽  
Midcontinent Rift ◽  
Geophysical Modeling ◽  
Western Lake

Rift-wide correlation of 1.1 Ga Midcontinent rift system basalts: implications for multiple mantle sources during rift development

1997 ◽  
Vol 34 (4) ◽  
pp. 504-520 ◽  
Author(s):  
Suzanne W. Nicholson ◽  
Klaus J. Schulz ◽  
Steven B. Shirey ◽  
John C. Green
Keyword(s):  
Mantle Source ◽  
Lake Superior ◽  
Flood Basalt ◽  
Great Depth ◽  
Rift System ◽  
Midcontinent Rift ◽  
Western Lake ◽  
Isotopic Analyses ◽  
Mantle Sources ◽  
Midcontinent Rift System

Magmatism that accompanied the 1.1 Ga Midcontinent rift system (MRS) is attributed to the upwelling and decompression melting of a mantle plume beneath North America. Five distinctive flood-basalt compositions are recognized in the rift-related basalt succession along the south shore of western Lake Superior, based on stratigraphically correlated major element, trace element, and Nd isotopic analyses. These distinctive compositions can be correlated with equivalent basalt types in comparable stratigraphic positions in other MRS localities around western Lake Superior. Four of these compositions are also recognized at Mamainse Point more than 200 km away in eastern Lake Superior. These regionally correlative basalt compositions provide the basis for determining the sequential contribution of various mantle sources to flood-basalt magmatism during rift development, extending a model originally developed for eastern Lake Superior. In this refined model, the earliest basalts were derived from small degrees of partial melting at great depth of an enriched, ocean-island-type plume mantle source (εNd(1100) value of about 0), followed by magmas representing melts from this plume source and interaction with another mantle source, most likely continental lithospheric mantle (εNd(1100) < 0). The relative contribution of this second mantle source diminished with time as larger degree partial melts of the plume became the dominant source for the voluminous younger basalts (εNd(1100) value of about 0). Towards the end of magmatism, mixtures of melts from the plume and a depleted asthenospheric mantle source became dominant (εNd(1100) = 0 to +3).

An investigation of Superior Shoal, central Lake Superior, with a manned submersible

1991 ◽  
Vol 28 (1) ◽  
pp. 145-150 ◽  
Author(s):  
Matthew L. Manson ◽  
Henry C. Halls
Keyword(s):  
Lake Superior ◽  
Complex Structure ◽  
Volcanic Rocks ◽  
Lava Flows ◽  
Basaltic Lava ◽  
Isle Royale ◽  
Midcontinent Rift ◽  
Boundary Fault ◽  
The North ◽  
Manned Submersible

A Johnson-Sea-Link submersible was used to examine the geology of Superior Shoal in central Lake Superior. Here, glacially scoured, vertical cliffs, some more than 100 m high, are formed of 1.1 Ga middle Keweenawan basaltic lava flows displaying ophitic interiors and red amygdaloidal tops. Flat-lying sandstones, lithologically similar to the upper Keweenawan Bayfield–Jacobsville sequences, occur to the north of the volcanic rocks. These are inferred to have been downthrown along an eastward extension of the Isle Royale fault, a major boundary fault of the Midcontinent rift. The volcanic rocks are normally magnetized, supporting lithological evidence that they correlate with the middle Keweenawan sequence on Isle Royale. Paleomagnetic data suggest that the volcanics have a complex structure, possibly involving drag folding along the Isle Royale fault.

Interpretation of seismic reflection and gravity profile data in western Lake Superior

1994 ◽  
Vol 31 (4) ◽  
pp. 652-660 ◽  
Author(s):  
John L. Sexton ◽  
Harvey Henson Jr.
Keyword(s):  
Fault Zone ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Lake Superior ◽  
Rift System ◽  
Isle Royale ◽  
Midcontinent Rift ◽  
Detachment Faults ◽  
Western Lake ◽  
Midcontinent Rift System

The interpretation of 1047 km of seismic reflection data collected in western Lake Superior is presented along with reflection traveltime contour maps and gravity models to understand the overall geometry of the Midcontinent Rift System beneath the lake. The Douglas, Isle Royale, and Keweenaw fault zones, clearly imaged on the seismic profiles, are interpreted to be large offset detachment faults associated with initial rifting. These faults have been reactivated as reverse faults with 3–5 km of throw. The Douglas Fault Zone is not directly connected with the Isle Royale Fault Zone. The seismic data has imaged two large basins filled with more than 22 km of middle Keweenawan pre-Portage Lake and Portage Lake volcanic rocks and up to 8 km of upper Keweenawan Oronto and Bayfield sedimentary rocks. These basins persisted throughout Keweenawan time and are separated by a ridge of Archean rocks and a narrow trough bounded by the Keweenaw Fault Zone to the south. Another fault zone, herein named the Ojibwa fault zone, previously interpreted as the northeastern extension of the Douglas Fault Zone, has been reinterpreted as a reverse fault that closely follows the ridge of Archean rocks. Previous researchers have stated that neighboring segments of the rift display alternating polarity of basins associated with large detachment faults. Accommodation zones have been previously interpreted to exist between rift segments; however, the seismic data do not image a clearly identifiable accommodation zone separating the two basins in western Lake Superior. Thus, the seismic profile may lie directly above the pivot of a scissors-type accommodation fault zone, there is no vertical offset associated with the zone, or the zone does not exist. Seismic data interpretations indicate that application of a simple alternating polarity basin – accommodation zone model is an oversimplification of the complex geological structures associated with the Midcontinent Rift System.

A geophysical profile of the southern margin of the midcontinent rift system in western Lake Superior

Tectonics ◽  
1990 ◽  
Vol 9 (2) ◽  
pp. 303-310 ◽  
Author(s):  
William J. Hinze ◽  
Lawrence W. Braile ◽  
Val W. Chandler
Keyword(s):  
Lake Superior ◽  
Rift System ◽  
Midcontinent Rift ◽  
Southern Margin ◽  
Western Lake ◽  
Midcontinent Rift System
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