Bedrock geologic map of Vermont

Ratcliffe, Nicholas M.; Stanley, Rolfe S.; Gale, Marjorie H.; Thompson, Peter J.; Walsh, Gregory J.; Rankin, Douglas W.; Doolan, Barry L.; Kim, Jonathan; Mehrtens, Charlotte J.; Aleinikoff, John N.; McHone, J. Gregory; Masonic, Linda M.

doi:10.3133/sim3184

Cited by 42 publications

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“…The bedrock geology of the Connecticut River Valley in western New Hampshire and eastern Vermont consists of highly deformed and metamorphosed Lower Paleozoic metasedimentary, metavolcanic, and metaplutonic rocks of the Bronson Hill arc and the Connecticut Valley trough ( Fig. 3; Lyons et al, 1997;Ratcliffe et al, 2011;. Rocks of the Bronson Hill arc are informally considered part of the New Hampshire sequence (Billings, 1935(Billings, , 1937White and Jahns, 1950;Rankin et al, 2013).…”

Section: ■ Geologic Settingmentioning

confidence: 99%

“…The Connecticut Valley trough lies unconformably or in local fault contact (McWilliams et al, 2010;Karabinos et al, 2010;Ratcliffe et al, 2011) atop remnants of the early Paleozoic volcanic arc rocks called the Shelburne Falls arc to the west (Karabinos et al, 1998;Karabinos and Hepburn, 2001) and the Bronson Hill arc to the east (Stanley and Ratcliffe, 1985;Ratcliffe et al, 1998;Tucker and Robinson, 1990;Leo, 1985Leo, , 1991Dorais et al, 2008Dorais et al, , 2012. The Connecticut Valley trough is composed of the Silurian to Devonian Shaw Mountain, Northfield, Waits River, and Gile Mountain Formations in an unconformable autochthonous cover sequence on the pre-Silurian rocks and Mesoproterozoic Laurentian basement rocks of the Mount Holly Complex in Vermont (Fig.…”

Section: ■ Geologic Settingmentioning

confidence: 99%

“…The Bronson Hill arc consists of metamorphosed mafic and felsic volcanic rocks (Ordovician Ammonoosuc Volcanics), felsic plutonic rocks (Ordovician Oliverian Plutonic Suite) of varying composition, and a metamorphosed cover sequence of graphitic-sulfidic schist, volcanic rocks, and minor quartzite (Ordovician Partridge Formation; Fig. 1; e.g., Billings, 1956;Zen et al, 1983;Tucker and Robinson, 1990;Lyons et al, 1997;Moench and Aleinikoff, 2003;Hollocher et al, 2002;Ratcliffe et al, 2011). The Partridge Formation is overlain by the Quimby Formation in northern New Hampshire and western Maine.…”

Section: ■ Introductionmentioning

confidence: 99%

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Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

et al. 2019

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U-Pb zircon geochronology by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) on 11 plutonic rocks and two volcanic rocks from the Bronson Hill arc in western New Hampshire yielded Early to Late Ordovician ages ranging from 475 to 445 Ma. Ages from Oliverian Plutonic Suite rocks that intrude a largely mafic lower section of the Ammonoosuc Volcanics ranged from 474.8 ± 5.2 to 460.2 ± 3.4 Ma. Metamorphosed felsic volcanic rocks from within the Ammonoosuc Volcanics yielded ages of 460.1 ± 2.4 and 455.0 ± 11 Ma. Younger Oliverian Plutonic Suite rocks that either intrude both the upper and lower Ammonoosuc Volcanics or Partridge Formation ranged in age from 456.1 ± 6.7 Ma to 445.2 ± 6.7 Ma. These new data and previously published results document extended magmatism for >30 m.y. The ages, along with the lack of mappable structural discontinuities between the plutons and their volcanic cover, suggest that the Bronson Hill arc was part of a relatively long-lived composite arc. The Early to Late Ordovician ages presented here overlap with previously determined igneous U-Pb zircon ages in the Shelburne Falls arc to the west, suggesting that the Bronson Hill arc and the Shelburne Falls arc could be part of one, long-lived composite arc system, in agreement with the interpretation that the Iapetus suture (Red Indian Line) lies to the west of the Shelburne Falls–Bronson Hill arc system.

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Section: ■ Geologic Settingmentioning

confidence: 99%

Section: ■ Geologic Settingmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

et al. 2019

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“…On the basis of lithologic similarities and rough stratigraphic position, numerous workers, for example, Billings (1956), Cady (1960), Hatch (1990), Zen (1983), Moench and Aleinikoff (2003), and Ratcliffe et al (2011), have suggested the correlation of the Albee Formation with the Moretown Formation in Vermont on the western side of the Connecticut Valley trough. Pinstriping is a characteristic of much of the micaceous sandstone of the Moretown Formation, as it is for much of the micaceous sandstone of the Albee and the Dead River Formations.…”

Section: Structural Argumentsmentioning

confidence: 99%

Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains-Bronson Hill stratigraphic sequence

Rankin

Tucker

Amelin

2012

Geological Society of America Bulletin

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The regional extent and mode and time of emplacement of the Piermont-Frontenac alloch thon in the Boundary Mountains-Bronson Hill anticlinorium of the Upper Connecticut Valley, New Hampshire-Vermont, are controversial. Moench and coworkers beginning in the 1980s proposed that much of the autoch thonous pre-Middle Ordovician section of the anticlinorium was a large allochthon of Silurian to Early Devonian rocks corre lated to those near Rangeley, Maine. This ~200-km-long allochthon was postulated to have been transported westward in the latest Silurian to Early Devonian as a soft-sedi ment gravity slide on a hypothesized Foster Hill fault. New mapping and U-Pb geo chronology do not support this interpretation. The undisputed Rangeley sequence in the Bean Brook slice is different from the disputed sequence in the proposed larger Piermont-Frontenac alloch thon, and fi eld evidence for the Foster Hill fault is lacking. At the type locality on Foster Hill, the postulated "fault" is a stratigraphic contact within the Ordovician Ammonoosuc Volcanics. The proposed Foster Hill fault would place the Piermont-Frontenac allochthon over the inverted limb of the Cornish(?) nappe, which includes the Emsian Littleton Formation, thus limiting the alleged sub marine slide to post-Emsian time. Mafi c dikes of the 419 Ma Comerford Intrusive Complex intrude previously folded strata attributed to the larger Piermont-Frontenac allochthon as well as the autochthonous Albee Formation and Ammonoosuc Volcanics. The Lost Nation pluton intruded and produced hornfels in previously deformed Albee strata. Zircons from an apophysis of the pluton in the hornfels have a thermal ionization mass spectrometry 207 Pb/ 206 Pb age of 444.1 ± 2.1 Ma. Tonal ite near Bath, New Hampshire, has a zircon sensitive high-resolution ion micro probe 206 Pb/ 238 U age of 492.5 ± 7.8 Ma. The tonalite intrudes the Albee Formation, formerly interpreted as the Silu rian Perry Mountain Formation of the proposed alloch thon. Collectively, these features indicate that the large Piermont-Frontenac allochthon gravity slide of Silurian-Devonian strata, as previously proposed, cannot exist. Alloch thonous rocks are restricted to a 25 km 2 klippe, the Bean Brook slice, emplaced by hard-rock thrusting in the post-Emsian Devonian. The Albee Formation, the oldest unit in the study area, is older than the Late Cambrian tonalite at Bath. The correlation and apparent continuity along strike to the northeast of the Albee Formation with the Dead River Formation suggest that the Albee Formation, like the Dead River Formation, is of Ganderian affi nity and that the Bronson Hill magmatic arc in the Upper Connecticut Valley was built on Ganderian crust. The Dead River Formation is unconformably overlain by Middle and Upper Ordovician volcanic units; the unconformity is attributed to the pre-Arenig Penobscottian orogeny. Some of the pre-Silurian deformation in the Upper Connecticut Valley may be Penobscottian rather than Taconian. New stratigraphic units defi ned herein include the pelitic...

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“…Domain 4 is unique because 038 is the dominant orientation and 060 lineaments are absent. The domains can be paired based on similarities in mean length: (1, 4),(2,5), and (3, 6). The length of the lineaments appear constant across a horizontal transect.…”

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confidence: 99%

Using Drone Surveys to Interpret the Geometry and Kinematics of a Mesozoic Fault Zone in Dolostones of the Champlain Valley Belt, West-Central Vermont

Remington¹,

Kim²,

Klepeis³

et al. 2017

Geological Society of America Abstracts With Programs

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The Champlain Valley Belt of west-central Vermont consists of CambrianOrdovician, weakly-metamorphosed, carbonate and clastic sedimentary rocks and is informally subdivided into 3 east-dipping lithotectonic slices, which are (from east to west): 1) the hanging wall of the Hinesburg Thrust (HWHT), 2) the hanging wall of the Champlain Thrust (HWCT), and 3) the Parautochthon. These thrust slices were juxtaposed during the Ordovician Taconian Orogeny and later modified by Acadian (Devonian) folding and Mesozoic extension. Our field area lies in the HWCT in a sliver of the Clarendon Springs Formation dolostone. This sliver is bounded by the Ordovician Muddy Brook Thrust (east) and the Mesozoic down-tothe-east St. George Fault (west).The field area consists of a 100m x 200m rectangle of continuous outcrop in a bedrock channel of the Winooski River at the Williston/Essex border. The northeast striking (~067) and steeply-dipping fault zone was first identified in 2014-2015 through detailed field mapping and structural analysis, however, drone surveys from altitudes of 41m (base map) and 26m (2 subdomains) were necessary to evaluate the geometry and kinematics of this zone. Field mapping of fractures and bedding were conducted at multiple scales using scangrids, scanlines, and pace and compass techniques.Photolineaments (n=715) were digitized using imagery captured by a UAV. The dominant azimuths are 067° (30%), 028° (29%), and 295° (14%). Average photolineament lengths for these groups are 3m, 2m, and 3m, respectively. By correlating photolineaments with field data, we confirmed that they represent steeply-dipping planes. The fault zone is defined by en echelon fractures with subhorizontal slickensides that strike 067° and step to the NW. Meter-scale scangrid arrays of the major fracture sets also corroborate this stepover direction. The style of deformation in stepovers will be used to determine fault zone kinematics. With the exception of local open folds, bedding strikes NW and dips moderately eastward, suggesting minimal displacement on all faults.Detailed mapping in other areas of west-central Vermont has identified other en echelon fault zones that strike toward 067° and cut across Paleozoic ductile structures. We suspect that they are related to motion on the St. George Fault. This photomosaic was constructed in GIS from multiple photos shot by the drone from an altitude of 41 m (135'). Photolineaments were digitized onto the mosaic using ArcMap software. Abstract Figure 7B-Fracture AttitudesThe dominant fractures sets strike ~060 and ~020 and dip steeply. m (30.5')A A' Figure 6C-Bedding Cross-SectionCross -Section A-A' was constructed ~parallel to the 060 fault zone and ~perpendicular to bedding, to see if the fault affected the attitude of bedding. Although the dip of bedding wobbles from station to station, there does not appear to be any major deflection caused by fault motion.The gentle folding is likely Paleozoic.FID on southeast side of fault zone (060 strike). Subhorizontal slickensides found ...

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Bedrock geologic map of Vermont

Cited by 42 publications

References 0 publications

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains-Bronson Hill stratigraphic sequence

Using Drone Surveys to Interpret the Geometry and Kinematics of a Mesozoic Fault Zone in Dolostones of the Champlain Valley Belt, West-Central Vermont

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