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The Neoproterozoic Jacobsville Sandstone outcrops along the south and east shores of Lake Superior, USA. It records intraplate deformation, some during its deposition and some afterwards, after the c. 1,100 Ma Midcontinent Rift (MCR) failed. Here we analyse 549 new detrital zircon ages from five sites, combined with prior data. Initially, local palaeo‐topography controlled the source material, including the MCR‐adjacent Penokean and Archaean rocks. With time the percentage of distal sources increased, including the c. 1,300–980 Ma Grenville orogeny and 1,480–1,360 Ma Granite‐Rhyolite Province. Sites near the Keweenaw fault contain a significant number of MCR‐age zircons, presumably uplifted to the surface, indicating fault motion during deposition. Only a relatively small percentage of 1,090–980 Ma Grenville‐age zircons from collisions to the east are present, suggesting that they were not efficiently transported to the Lake Superior area. This work is innovative in that it is the first to use detrital zircon geochronology to understand the internal stratigraphy of the Jacobsville Sandstone, whose provenance provides new information about the Neoproterozoic tectonic and sedimentary history of Laurentia. [ABSTRACT FROM AUTHOR]

Highlights • This is a first study of variations in rock strains along and across the Penokean orogen. • We also incorporate strains measured in the northern Archean foreland and the younger Yavapai (1750 Ma) and Mazatzal (1630 Ma) orogens. • New paleomagnetic and geochronologic data is also included as part of this regional synthesis. Abstract Strata in the Huron (2.5–2.0 Ga) and Animikie (2.2–1.85 Ga) basins were deposited on the southern margin of the Archean Superior province. These rocks were deformed during the Penokean orogeny (∼1850 Ma) followed by subsequent accretionary orogens to the south at 1750 Ma (Yavapai) and 1630 Ma (Mazatzal). Strain patterns are unique to each orogenic belt with no far-field effect: Archean Wawa terrane rocks in the Penokean foreland preserve deformation associated with Archean accretion with no younger Penokean, Yavapai or Mazatzal strain overprint. The Penokean orogeny deformed Huron-Animikie basin sediments into a north-vergent fold-and-thrust belt with no Yavapai or Mazatzal strain overprint. Yavapai orogen strains (SW-NE margin-parallel shortening) are unique when compared to the younger Mazatzal shortening (N20°W) shortening, with no strain overprint. Penokean deformation is characterized by shortening from the south including uplifted Archean gneisses and a northerly thin-skinned fold-and-thrust belt, with north-vergent nappes and a gently-dipping foreland. Our study of finite and calcite twinning strains (n = 60) along (∼1500 km) and across (∼200 km) the Penokean belt indicate that this orogeny was collisional as layer-parallel shortening axes are parallel across the belt, or parallel to the tectonic transport direction (∼N-S). Penokean nappe burial near the margin resulted in vertical shortening strain overprints, some of which are layer-normal. The Sudbury impact layer (1850 Ma) is found across the Animikie basin and provides a widespread deformation marker with many local, unique strain observations. We also report new geochronology (U-Pb zircon and apatite) for the gneiss-mafic dike rocks at Wissota (Chippewa Falls, WI) and Arbutus (Black River Falls, WI) dams, respectively, which bears on Penokean-Yavapai deformation in the Archean Marshfield terrane which was accreted during the Penokean orogen. Pseudotachylite formation was common in the Superior province Archean basement rocks, especially along terrane boundaries reactivated by contemporaneous Penokean, Trans-Hudson, Cape Smith and New Quebec deformation. In the hinterland (south), the younger Yavapai orogen (1750 Ma; n = 8) deformation is preserved as margin-parallel horizontal shortening (∼SW-NE) in Yavapai crust and up to 200 km to the north in the Penokean thrust belt as a strain and Barrovian metamorphic overprint. Mazatzal deformation (1630 Ma; n = 16) is preserved in quartzites on Yavapai and Penokean crust with layer-parallel and layer-normal shortening strains oriented N20°W. [ABSTRACT FROM AUTHOR]

This study uses detrital zircon U-Pb geochronology from shallow-water carbonates of the Bighorn Dolomite in Wyoming, USA, to provide robust evidence for long-distance eolian sediment transport during the Ordovician. The Bighorn Dolomite was deposited in a shallow-water carbonate platform that developed approximately 10° south of the Ordovician paleoequator on the western edge of Laurentia. The ages and textures of detrital zircons from the Bighorn indicate that the grains were transported by winds through saltation and suspension from the paleo east where rocks of the Paleoproterozoic Trans- Hudson orogenic belt were exposed in present-day Manitoba and Saskatchewan. Our interpretation of long-distance eolian transport is consistent with the paleogeography of Laurentia and expected prevailing wind directions and draws on modern analogs where Saharan sediment is transported by trade winds for distances of more than 3000 km. [ABSTRACT FROM AUTHOR]

Quartz arenites characterize much of the early Paleozoic sedimentary history of the midcontinent region. Despite numerous studies, the century-long debate on how these arenites formed is still unresolved, primarily because of the compositional and textural purity of the deposits. In this study, we present an extensive data set of detrital zircon geochronology from the early Paleozoic supermature arenites of the midcontinent region, and we offer newconstraints about their origin. Our results coupled with compiled provenance information from older basins and orogens may indicate that the Cambrian and Ordovician arenites represent sediment reworking primarily of two different older basins. The Cambro-Ordovician sediment was transported to the midcontinent region by two early Paleozoic river systems that sourced from the paleo-east (Huron basin) and paleo-northeast (midcontinent rift region). [ABSTRACT FROM AUTHOR]

The Archean nucleus of Laurentia, the Superior province, formed between 2.7 and 2.6 Ga. There is little record of sediment deposition on the craton for 100 m.yr. until deposition of the Huronian clastic sedimentary rocks (4-12 km thick) began along the south-central margin of the Superior province between 2.5 and 2.2 Ga. Huronian detrital zircon ages ( zircon SHRIMP 207Pbx/206Pbx np266 ages from six samples) are dominantly 2.6-2.7 Ga, with a small population aged 3.0-3.5 Ga in the middle of the Huron section. The mainly younger, and western, Animikie basin (6-12 km thick; 2.21-0.8 Ga) contains a wide range of nearshore and deep-water clastic rocks, including banded iron formations and the 1.85 Ga Sudbury "impactite" deposits with overlying turbidites. Animikie detrital zircon ages (np724 laser ablation ICP-MS 207Pbx/206Pbx zircon ages from 10 samples) contain a complex spectrum, with ages ranging from 1.8 to 3.8 Ga: the basal Chocolay (Denham, East Branch Arkose) samples contain zircons ranging in age from 2.1 to 3.7 Ga, with a dominant population at ~2.6 Ga; the basal Animikie (Menominee) quartzites contain zircons with ages between 2.1 and 3.8 Ga, with peaks variably at 2.1, 2.3, 2.6, and 3.0 Ga; the upper Animikie (Baraga) turbidites contain zircons with ages between 1.8 and 3.6 Ga, with a dominant peak at 1.85 Ga. The Huron and Animikie basins were intensely deformed by Penokean orogenic (1.85 Ga) accretion from the south. Deposition into the Huron basin was from the north and west for 200 m.yr.; then the depocenter shifted to the west at ~2.2 Ga, with the Animikie basin receiving clastic debris from all directions, including from terranes (e.g., Marshfield and the Wisconsin Magmatic Terrane) approaching from the south. Combined Huron and Animikie detrital zircon results record a migrating eastto- west depocenter, perhaps in conjunction with the dynamics of the central Marathon large igneous province mantle plume and dike swarm (~2.07 Ga), over a period of 500 m.yr. [ABSTRACT FROM AUTHOR]

Abstract: Two perpendicular ultramafic lamprophyre dikes on Little Presque Isle near Marquette, Michigan were studied to compare their intrusive magmatic fabric using anisotropy of magnetic susceptibility (AMS) with the strains preserved by mechanical twins in dike magmatic calcite (δ 18O=−21.93, δ 13C=−4.53) and dike-margin hydrothermal calcite (δ 18O=−9.72, δ 13C=−3.76) veins. Phlogopite from the lamprophyres yield an 40Ar–39Ar plateau age of 1877Ma, and the lamprophyres intrude metadiabase dikes and the Compeau Creek gneiss (2691±25 Ma; LA-ICPMS U–Pb on zircon), all of which is cross-cut by Keweenaw basaltic dikes and unconformably overlain by the undeformed Jacobsville Sandstone (Meso- to Neoproterozoic). The lamprophyre dikes strike east–west and north–south in this small (3km2), complex outcrop. Analysis of mechanically twinned calcite in the E–W dike (n =89 grains, 26.97% NEVs) reveals a sub-horizontal dike-acute shortening strain axis (N38°E, 15°). Strain analysis of the N–S dike (n =107 grains, 22.43% NEVs) reveals a sub-horizontal and dike-parallel shortening strain axis (N17°E, 14°). Calcite veins from the margins of both lamprophyre dikes reveal a NE–SW sub-horizontal shortening, and both the lamprophyres and vein calcite preserve a vertical shortening strain overprint. Differential stress magnitudes for twinning the lamprophyre calcite and adjacent veins was −35MPa. AMS analyses, used as a proxy for the primary magmatic flow direction, reveal a sub-horizontal and dike-parallel K max, with a dike-normal K min for the E–W dike. The N–S dike preserves a vertical K max and a dike-normal K min. Hysteresis studies on both dikes show that this anisotropy is carried by multi-domain ferromagnetic minerals. These lamprophyres preserve a complex, local intrusive fabric (AMS) that was unaltered by Penokean sub-horizontal shortening (∼SW–NE), or the younger, sub-vertical shortening strain overprint ∼200km inboard of the unrestored Penokean margin. The twinning strain results are consistent with other Penokean finite strains but not with the strain fabrics of younger orogens (e.g., Yavapai, Mazatzal, Keweenaw-Grenville). [Copyright &y& Elsevier]