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Blockhouse Formation

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Stratigraphic columns for the Piedmont Province directly north of the Potomac River, plus the Baltimore terrane. All these rocks have been metamorphosed; the columns depict the protolith lithologies. Constraints on depositional ages are in Table 1. The northern Mather Gorge Formation is not included in this diagram. Sugarloaf MQ—Sugarloaf Mountain Quartzite; Blockhouse Pt.—Blockhouse Point domain of the Mather Gorge Formation; Bear Island—Bear Island domain of the Mather Gorge Formation; NW Branch—Northwest Branch Formation.

Stratigraphic columns for the Piedmont Province directly north of the Potom... Open Access

Published: 01 August 2015
is not included in this diagram. Sugarloaf MQ—Sugarloaf Mountain Quartzite; Blockhouse Pt.—Blockhouse Point domain of the Mather Gorge Formation; Bear Island—Bear Island domain of the Mather Gorge Formation; NW Branch—Northwest Branch Formation.
Journal Article

Contrasting tectonothermal domains and faulting in the Potomac terrane, Virginia–Maryland—discrimination by 40 Ar/ 39 Ar and fission-track thermochronology Available to Purchase

Michael J. Kunk, Robert P. Wintsch, Charles W. Naeser, Nancy D. Naeser, C. Scott Southworth, Avery A. Drake, Jr., Jennifer L. Becker
Journal: GSA Bulletin
Published: 01 September 2005
GSA Bulletin (2005) 117 (9-10): 1347–1366.
DOI: https://doi.org/10.1130/B25599.1
... ; Drake, 1989 ). In this study at least two domains are identified within the Mather Gorge Formation, the Blockhouse Point and Bear Island domains, on the basis of their distinct thermal and metamorphic histories. The boundary between these two domains appears to be tectonic and not one...
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View PDF for article title, Contrasting tectonothermal domains and faulting in the Potomac terrane, Virginia–Maryland—discrimination by 40 Ar/ 39 Ar and fission-track thermochronology
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A temperature-time (T-t) diagram comparing the Paleozoic thermal histories of the four cleavage domains examined here, the Blockhouse Point (dark green), Germantown (pale green), Hyattstown (blue) domains, and Frederick Valley synclinorium (violet), with the Bear Island (orange) and the Sykesville (red) domains from Kunk et al. (2005). Histories are constrained by crystallization (xl) (plateau) ages of muscovite in the cleavages in the Hyattstown and Blockhouse Point domains, and by cooling ages of biotite and K-feldspar. Cleavage generations (wavy lines) are identified S1 through S4. Time of orogenies (vertical gray bands) from Rankin (1994) and Ettensohn (2008). Typical closure temperatures of amphibole, muscovite, biotite, and K-feldspar (horizontal gray bands) from McDougall and Harrison (1999). Temperature of the biotite isograd in K-feldspar–bearing assemblages (∼320 °C) from Bird and Spieler (2004). Depositional ages of the Shawangunk and Bloomsburg formations from Ettensohn (2008). Time scale from Gradstein et al. (2004). Abbreviations: Amp—amphibole; BP—Blockhouse Point domain; Bt—biotite; Camb—Cambrian; Cld—chloritoid; FVS—Frederick Valley synclinorium; Gt—Germantown domain; Ht—Hyattstown domain; Jur—Jurassic; Kf—K-feldspar; L.Prot.—Lower Proterozoic; Miss—Mississippian; Mu—muscovite; Penn—Pennsylvanian; W&G—Wise and Gannis, 2009; xliz.—crystallization.

A temperature-time (T-t) diagram comparing the Paleozoic thermal histories ... Available to Purchase

Published: 01 May 2010
) from Bird and Spieler (2004) . Depositional ages of the Shawangunk and Bloomsburg formations from Ettensohn (2008) . Time scale from Gradstein et al. (2004) . Abbreviations: Amp—amphibole; BP—Blockhouse Point domain; Bt—biotite; Camb—Cambrian; Cld—chloritoid; FVS—Frederick Valley synclinorium; Gt
Journal Article

Contrast in the process response of stacked clinothems to the shelf-slope rollover Open Access

George E.D. Jones, David M. Hodgson, Stephen S. Flint
Journal: Geosphere
Published: 01 April 2013
Geosphere (2013) 9 (2): 299–316.
DOI: https://doi.org/10.1130/GES00796.1
... the lower Waterford Formation. The stepped morphology, the orientation with regional paleoflow, and the paleogeographic context support an interpretation that the scours represent straight shelf-edge to upper slope gullies. The 2D dip profile of the Blockhouse section means that the wedges are well...
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Journal Article

40 Ar/ 39 Ar dating of Silurian and Late Devonian cleavages in lower greenschist-facies rocks in the Westminster terrane, Maryland, USA Available to Purchase

R.P. Wintsch, M.J. Kunk, B.K. Mulvey, C.S. Southworth
Journal: GSA Bulletin
Published: 01 May 2010
GSA Bulletin (2010) 122 (5-6): 658–677.
DOI: https://doi.org/10.1130/B30030.1
...) from Bird and Spieler (2004) . Depositional ages of the Shawangunk and Bloomsburg formations from Ettensohn (2008) . Time scale from Gradstein et al. (2004) . Abbreviations: Amp—amphibole; BP—Blockhouse Point domain; Bt—biotite; Camb—Cambrian; Cld—chloritoid; FVS—Frederick Valley synclinorium; Gt...
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View PDF for article title, 40 Ar/ 39 Ar dating of Silurian and Late Devonian cleavages in lower greenschist-facies rocks in the Westminster terrane, Maryland, USA
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Taxa by locality for new material described herein from the Platteville For... Available to Purchase

Published: 01 March 2019
Table 1. Taxa by locality for new material described herein from the Platteville Formation of southern Wisconsin. Localities as follows: 1, Dickeyville; 2, Snowdon Creek; 3, Blockhouse Creek; 4, New Glarus; 5, Sun Prairie; 6, Columbus. See text for detailed locality information. Species
Image
Geographic outcrop distribution of the previously recognised paleogeographic parts of the lower Miocene Waitemata Basin in the Auckland, southern Northland and northern Waikato regions of New Zealand (adapted from Ballance, 1974; Hayward, 1993; Isaac et al., 1994; Edbrooke, 2001; Edbrooke & Brook, 2009). The central part of the Waitemata Basin (Warkworth Subgroup) is divided into the following facies: basal transgressive facies (Kawau Subgroup); volcanic-poor flysch (East Coast Bays Formation); volcanic-rich flysch (Pakiri Formation); mixed volcanic-rich and volcanic-poor flysch (Blockhouse Bay and Cornwallis formations); and northwest slope facies (Timber Bay and Waihangaru formations and associated conglomerates – Albany, Matapoura and Helensville). Inset location map of North Island, New Zealand.

Geographic outcrop distribution of the previously recognised paleogeographi... Available to Purchase

Published: 01 July 2016
flysch (Blockhouse Bay and Cornwallis formations); and northwest slope facies (Timber Bay and Waihangaru formations and associated conglomerates – Albany, Matapoura and Helensville). Inset location map of North Island, New Zealand.
Image
Figure 6. Cooling curves for Blockhouse Point domain (Mather Gorge complex [MGC]), Bear Island domain (Mather Gorge complex), and Sykesville Formation. Filled circles—amphibole cooling, open star—Rb/Sr muscovite cooling, open triangle—muscovite cooling, filled triangle—biotite cooling, filled diamond—muscovite growth, filled hexagon—U/Pb zircon growth, open hexagon—U/Pb zircon overgrowth, and ZFT—zircon fission-track cooling. All U/Pb zircon age data are on the Sykesville Formation cooling curve. The ZFT box is drawn at 282 ± 13 Ma and 235 ± 25 °C (see text).

Figure 6. Cooling curves for Blockhouse Point domain (Mather Gorge complex ... Available to Purchase

Published: 01 September 2005
Figure 6. Cooling curves for Blockhouse Point domain (Mather Gorge complex [MGC]), Bear Island domain (Mather Gorge complex), and Sykesville Formation. Filled circles—amphibole cooling, open star—Rb/Sr muscovite cooling, open triangle—muscovite cooling, filled triangle—biotite cooling, filled
Journal Article

Laurentian and Amazonian sediment sources to Neoproterozoic–lower Paleozoic Maryland Piedmont rocks Open Access

Aaron J. Martin, Scott Southworth, Jennifer C. Collins, Steven W. Fisher, Edward R. Kingman, III
Journal: Geosphere
Published: 01 August 2015
Geosphere (2015) 11 (4): 1042–1061.
DOI: https://doi.org/10.1130/GES01140.1
... is not included in this diagram. Sugarloaf MQ—Sugarloaf Mountain Quartzite; Blockhouse Pt.—Blockhouse Point domain of the Mather Gorge Formation; Bear Island—Bear Island domain of the Mather Gorge Formation; NW Branch—Northwest Branch Formation. ...
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View PDF for article title, Laurentian and Amazonian sediment sources to Neoproterozoic–lower Paleozoic Maryland Piedmont rocks
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Journal Article

Paleotectonic Implications of a Mid- to Late-Ordovician Provenance Shift, as Recorded in Sedimentary Strata of the Ouachita and Southern Appalachian Mountains Available to Purchase

James D. Gleason, Stanley C. Finney, George E. Gehrels
Published: 01 May 2002
The Journal of Geology (2002) 110 (3): 291–304.
DOI: https://doi.org/10.1086/339533
..., is slightly more negative (−9.9). These values are similar (though less variable) to those obtained for the lower ( H. teretiusculus zone) Blockhouse Formation (−10.0 and −9.4) and upper ( N. gracilis zone) Blockhouse Formation (−7 to −8) of the Sevier basin, Tennessee, by Andersen and Samson ( 1995...
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View PDF for article title, Paleotectonic Implications of a Mid- to Late-Ordovician Provenance Shift, as Recorded in Sedimentary Strata of the Ouachita and Southern Appalachian Mountains
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Journal Article

Previously melt-depleted mantle beneath the Cascades Range arc Available to Purchase

Ian Yuh, James M.D. Day
Journal: Geology
Published: 19 July 2023
Geology (2023) 51 (10): 909–913.
DOI: https://doi.org/10.1130/G51376.1
... xenoliths were examined from a larger suite of samples. Samples were collected from Lorena Butte, except for two trachybasalts, which were collected ~15 km NW at Blockhouse Butte. Peridotite xenoliths are ~5–10 cm harzburgites; dunites, wehrlites, olivine-websterites, websterites, and olivine...
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View PDF for article title, Previously melt-depleted mantle beneath the Cascades Range arc
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Journal Article

MIDDLE ORDOVICIAN (CHAZYAN) SEA-LEVEL CHANGES AND THE EVOLUTION OF THE ORDOVICIAN CONODONT GENUS CAHABAGNATHUS BERGSTRÖM, 1983 Available to Purchase

STEPHEN A. LESLIE, OLIVER LEHNERT
Published: 01 November 2005
Journal of Paleontology (2005) 79 (6): 1131–1142.
DOI: https://doi.org/10.1666/0022-3360(2005)079[1131:MOCSCA]2.0.CO;2
... of both Midcontinent and North Atlantic taxa. This supports the idea that in this sample C. friendsvillensis may have been transported postmortem from a shallow water setting into a deeper water environment. The fauna associated with C. friendsvillensis from limestone beds in the Blockhouse Shale...
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View PDF for article title, MIDDLE ORDOVICIAN (CHAZYAN) SEA-LEVEL CHANGES AND THE EVOLUTION OF THE ORDOVICIAN CONODONT GENUS CAHABAGNATHUS BERGSTRÖM, 1983
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Journal Article

New Ordovician marine macroalgae from North America, with observations on Buthograptus , Callithamnopsis , and Chaetocladus Available to Purchase

Steven T. LoDuca
Published: 01 March 2019
Journal of Paleontology (2019) 93 (2): 197–214.
DOI: https://doi.org/10.1017/jpa.2018.76
...Table 1. Taxa by locality for new material described herein from the Platteville Formation of southern Wisconsin. Localities as follows: 1, Dickeyville; 2, Snowdon Creek; 3, Blockhouse Creek; 4, New Glarus; 5, Sun Prairie; 6, Columbus. See text for detailed locality information. Species...
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View PDF for article title, New Ordovician marine macroalgae from North America, with observations on Buthograptus , Callithamnopsis , and Chaetocladus
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Journal Article

Reliability of Glauconite for Age Measurement by K-Ar and Rb-Sr Methods Available to Purchase

P. M. Hurley, R. F. Cormier, J. Hower, H. W. Fairbairn, W. H. Pinson, Jr.
Journal: AAPG Bulletin
Published: 01 November 1960
AAPG Bulletin (1960) 44 (11): 1793–1808.
DOI: https://doi.org/10.1306/0BDA6245-16BD-11D7-8645000102C1865D
... formation in which they found an age ratio equivalent to 443 m.y., if corrected to the constants used in this paper. The analytical details are included in Table I , as they are of interest in comparison with the present report of K 40 and Ar 40 from other samples from the same formation. Goldich...
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View PDF for article title, Reliability of Glauconite for Age Measurement by K-Ar and Rb-Sr Methods
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Journal Article

Geodynamic Models of Convergent Margin Tectonics: Transition from Rifted Margin to Overthrust Belt and Consequences for Foreland-Basin Development Available to Purchase

Glen S. Stockmal, Christopher Beaumont, Ross Boutilier
Journal: AAPG Bulletin
Published: 01 February 1986
AAPG Bulletin (1986) 70 (2): 181–190.
DOI: https://doi.org/10.1306/94885656-1704-11D7-8645000102C1865D
.... Delany, eds., Zagros, Hindu Kush, Himalaya geodynamic evolution : American Geophysical Union Geodynamics Series , v. 3 , p. 215 – 242 . Shanmugam , G. , and K. R. Walker , 1978 , Tectonic significance of distal turbidites in the Middle Ordovician Blockhouse and lower Sevier Formations...
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View PDF for article title, Geodynamic Models of Convergent Margin Tectonics: Transition from Rifted Margin to Overthrust Belt and Consequences for Foreland-Basin Development
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Book Chapter

Lead and zinc mining in the Driftless Area Available to Purchase

Author(s)
James C. Knox*
Book: The Physical Geography and Geology of the Driftless Area: The Career and Contributions of James C. Knox
Series: GSA Special Papers
Publisher: Geological Society of America
Published: 15 October 2019
DOI: 10.1130/2019.2543(08)
EISBN: 9780813795430
... are concentrated in Ordovician age strata, although minor deposits also occur in Cambrian- and Silurian-age strata near the margins of the district ( Heyl et al., 1959 , 1978 ). The principal ore deposits occur in the middle Ordovician, Sinnipee Group, Galena, Decorah, and Platteville formations. Concentrations...
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Abstract
View PDF for content titled, Lead and zinc mining in the Driftless Area
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ABSTRACT Lead and zinc ore minerals occur in the middle Ordovician Sinnipee Group dolomites in southwest Wisconsin and adjacent areas of northwest Illinois and northeast Iowa. Europeans began mining lead deposits as early as the mid-1600s; production of lead ore and smelting of lead reached a peak ca. 1850. Mining and production from the stratigraphically lower zinc deposits reached a peak in 1917, with a lesser resurgence of zinc production ca. 1950–1970. The mining detritus and sediment from mine waste piles is relatively stable. However, cations of lead and zinc freely adsorb to clay and silt particles and have been incorporated into the downstream fluvial systems. The temporal coincidence of lead-zinc mining and active aggradation of many fluvial systems in the Driftless Area has resulted in these “legacy sediments” being preserved in overbank fluvial deposits throughout the Lead-Zinc District.

Journal Article

Geophysical Imaging of Subsurface Earthquake-induced Liquefaction Features at Christchurch Boys High School, Christchurch, New Zealand Available to Purchase

David C. Nobes, Sarah Bastin, Gemma Charlton, Rowan Cook, Max Gallagher, Hamish Graham, Daniel Grose, Joanne Hedley, Scott Sharp-Heward, Sean Templeton
Published: 01 December 2013
Journal of Environmental and Engineering Geophysics (2013) 18 (4): 255–267.
DOI: https://doi.org/10.2113/JEEG18.4.255
... 22, 2011, liquefaction occurred at many spots on the sports grounds at Christchurch Boys High School (CBHS, Fig. ). CBHS is sited northwest of the Christchurch central city, and is underlain by interbedded sands, silts and gravels of the Christchurch and Springston formations ( Brown et al., 1988...
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View PDF for article title, Geophysical Imaging of Subsurface Earthquake-induced Liquefaction Features at Christchurch Boys High School, Christchurch, New Zealand
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Journal Article

Depositional Response to Foreland Deformation in the Carboniferous of Eastern Kentucky Available to Purchase

Anthony J. Tankard
Journal: AAPG Bulletin
Published: 01 July 1986
AAPG Bulletin (1986) 70 (7): 853–868.
DOI: https://doi.org/10.1306/9488635D-1704-11D7-8645000102C1865D
... and, because of Airy regional compensation, created little relief above sea level ( Quinlan and Beaumont, 1984 ). The early foredeep was 700-2,000 m (2,300-6,500 ft) deep and shale dominated (e.g., Blockhouse formation) ( Shanmugam and Lash, 1982 ; Walker et al, 1983 ). Transition from passive to convergent...
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View PDF for article title, Depositional Response to Foreland Deformation in the Carboniferous of Eastern Kentucky
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USING MULTI-FORAMINIFERAL-PROXIES TO RESOLVE THE PALEOGEOGRAPHIC HISTORY OF A LOWER MIOCENE, SUBDUCTION-RELATED, SEDIMENTARY BASIN (WAITEMATA BASIN, NEW ZEALAND) Available to Purchase

Bruce W. Hayward, Christopher M. Triggs
Published: 01 July 2016
Journal of Foraminiferal Research (2016) 46 (3): 285–313.
DOI: https://doi.org/10.2113/gsjfr.46.3.285
... flysch (Blockhouse Bay and Cornwallis formations); and northwest slope facies (Timber Bay and Waihangaru formations and associated conglomerates – Albany, Matapoura and Helensville). Inset location map of North Island, New Zealand. ...
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View PDF for article title, USING MULTI-FORAMINIFERAL-PROXIES TO RESOLVE THE PALEOGEOGRAPHIC HISTORY OF A LOWER MIOCENE, SUBDUCTION-RELATED, SEDIMENTARY BASIN (WAITEMATA BASIN, NEW ZEALAND)
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Journal Article

Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: Characteristics, extent, and tectonic significance Available to Purchase

James Tull, Christopher S. Holm-Denoma, Clinton I. Barineau
Journal: GSA Bulletin
Published: 01 July 2014
GSA Bulletin (2014) 126 (7-8): 990–1015.
DOI: https://doi.org/10.1130/B30967.1
... of the Blockhouse Formation ( Shanmugam and Walker, 1980 ; Kolata et al., 1996 ). One K-bentonite is found near the base (lower 10%) of the Rockmart Slate ( Bayona, 2006 ). Using the composite standard reference sections of graptolites, along with U-Pb zircon dating of ash beds within the upper Llanvirnian...
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View PDF for article title, Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: Characteristics, extent, and tectonic significance
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