Chirigos, Kim, Klepeis, and Van Hoesen, 2016, Using

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Using Photogrammetry to Analyze Structures in a Tectonic Sliver in the Foot Wall of the Champlain Thrust, Shelburne, Vermont II Vermont Geological Survey Technical Report VGTR16-2 1 2 1 3 Chirigos, Michael ; Kim, Jonathan ; Klepeis, Keith , and Van Hoesen, John Shelburne Farms Lake Outcrop Summary Data

1 2 3 Poles to So Poles to S1 Poles to S2 and S2.5 All F2 Fold Data Dept. of Geology, University of Vermont, Burlington, VT 05405, [email protected]; Vermont Geological Survey, 1 National Life Drive, Montpelier, VT 05620; Green Mountain College, One College Circle, Poultney, VT 05764 N N N N

Shelburne Farms Lake Outcrop 3D Block Diagram Abstract North 270 90 270 90 90 270 90 In the Champlain Valley Belt of west-central Vermont, the Champlain West East Thrust juxtaposed ferruginous quartzites and dolostones of the Lower Cambrian Figure 1- Lithotectonic Base Map. Figure 2- Bedrock Geology. C’ Monkton Fm (hanging wall) with calcareous shales of the Late Ordovician Stony Figure 3- Detailed Base Map for the Study Area. SP4A S2 SP4B Airphoto base for the study area that shows the outcrop extent (red), the extent of each of the five Structural Packages (SP)(yellow), the locations of bounding faults (yellow pins), and the attitudes F2 270 Point Fm (foot wall = Parautochthon), during the Ordovician Taconian Orogeny. of the faults (blue symbols). The magenta arrows delineate the limits of the 3D outcrop mosaics directly below. n = 26 n = 155 S2 n = 24 Internal to the Parautochthon in this area, a tectonic sliver of dark gray limestone is S2.5 n = 2 Clockwise rotation of fold axial 180 180 180 180 found that likely correlates with the Cumberland Head Fm. D Calculated F2 fold axes n = 27 planes provides both timing and Measured So/S1 intersection lineations n = 8 sense of shear on decollement. Key: Structural analysis of a ~100 m long outcrop was accomplished through a So: Blue Measured So/S1 intersection lineations: Dark Green Calculated So/S1 intersection lineations n = 19 Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue Measured S1/S2 intersection lineations n = 5 combination of photogrammetric techniques and field measurements. We used B C Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink Calculated S1/S2 intersection lineations n = 25 Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown photogrammetry software to construct photo mosaics of 1) the entire outcrop, 2) A Package 4: Calculated F2 Package 5: fold Axes: Black each structural package, and 3) across the tectonic boundaries between structural F2 packages. A preliminary structural synthesis is described below. It is important to ++ point out that structures with the same relative age, determined using cross cutting Figure 6B- Summary data for all structural packages in the study area. relationships, may have developed diachronously across the outcrop. SP5 The “sliver” of Cumberland Head Fm consists of 5 structural packages that So are bounded by 4 faults. The oldest planar structure in each package is bedding Shelburne Farms Outcrop Fault Data (S ), which appears as a millimeter-scale, dark and light, compositional banding. + 0 + Fault A Planes Fault B Planes and Slickenlines Fault D Planes and Slickenlines So S2.5 Fault C Planes and Slickenlines Superposed on S0 at high angles, is a penetrative spaced pressure-solution cleavage C N N N N S2 Fault Planes n = 3 S1 that, where associated folds are absent, is thrust-related. Southeast-trending Fault planes n = 5 Fault Planes n = 7 Fault Planes n = 3 Slickenlines n = 2 S1 Slickenlines n = 6 slickensides formed on fault-parallel zones of calcite veins in each of the 4 faults. S1 Stage 2 Slickenlines n = 3 STUDY In packages 1-3 (numbered from west to east), S1 is truncated by, and/or AREA B Stage 1 rotated into parallelism with, the overriding east-dipping thrust faults. These faults SP1 Inferred Decollement A SP3 Fault: 90 SP5 Stage 3 Key: 270 90 270 90 270 90 270 (A+B) are deformed by open folds (F2) with a local axial planar spaced cleavage Inferred Fault: SP3 SP4 Slickenlines: (S2). The fault C boundary between packages 3 and 4 truncates S2. Although the S1 SP2 So: 73 S1: Slip/Fault cleavage is openly folded (F3) and fans on the west side of package 4, it shears out Motion 37 S2: on the east side to form a ~vertical fault contact with package 5. Within package 5, 20 S2.5: Indicator: SP2 Hinterland Propagation in Three Stages S is deformed by tight reclined F folds, with gently south-plunging axes. F2 Fold Axes: Second generation 1 3 Motion indicator: Stage 1: Development of Faults A and B Overturned 180 180 Key: 180 180 SP1 Indicates perspective This poster shows photo mosaics of different scales that are integrated with Stage 2: Formation of Fault C followed by Faults C’ and D Anticline: Fault Plane: 51 Stage 3: Onset of Back folding and the inferred decollement into outcrop: ++ Slickenlines: field data to document the structural history of the Shelburne outcrop. Our approach illustrates the utility of using photogrammetric techniques in the General study area and lithotectonic belts on bedrock geologic map (modified from Ratcliffe et al. (2011). Figure 6C- Summary data of faults in the study area. structural analysis of complexly deformed outcrops. Inset from Figure 1 showing the bedrock geology of the study area (modified from Ratcliffe et al. (2011)). The study area is the yellow Figure 6A- 3D block diagram of the study area. polygon.

Figure 6D - Evolution of S1 Pressure-Solution Cleavage from West to East.

WEST EAST Legend for Planar Structures SP3 Fault SP2 Fault B SP4A S 2.5 cleavage Fault C’ S 2 cleavage SP4A SP4B Fault B SP3 SP2 Fault C’ S1 pressure solution cleavage Fault A Fault C SP1 Fault D S0 bedding SP4B Fault C SP5 Major fracture

S pressure-solution cleavage on the western side of SP5 that was deformed S pressure-solution cleavage on the eastern side of SP5 that was deformed S1 pressure-solution cleavage (green) in SP2 below Fault B. Note bedding(S0) 1 1 S1 pressure-solution cleavage on the central part of SP5 that was deformed by open F folds. Note bedding(S ) in the microlithons. by tight F folds. Note bedding(S ) in the S1 microlithons and the S fracture (blue) in the microlithons that makes a pronounced intesection lineation (L1) 2 0 2 0 2 by very tight F2 folds. Note that bedding(S0) in the S1 microlithons (parallel Figure 4A- Western 3D Outcrop Mosaic. cleavage that is axial planar to the F folds and fortuitously parallel to S . Figure 4B- Central 3D Outcrop Mosaic. Figure 4C- Eastern 3D Outcrop Mosaic (west side). Figure 4D- Eastern 3D Outcrop Mosaic (east side). on S1. 2 0 to pen) is now subvertical.

WEST EAST SP2 SP5 Fault A SP4A SP3 Fault C’ SP4B SP3 Fault C SP4A Fault B

Fault D

SP1 Fault D Fault C SP5 SP2 SP3 SP5 Station 112015-3L

Figure 4A- Annotated photo mosaic of the Fault A boundary between SP1 and SP2. Figure 4B- Annotated photo mosaic of the Fault B boundary between SP2 and SP3. Figure 4C- Annotated photo mosaic of SP3 before truncation by Fault C. Figure 4D- Annotated photo mosaic spanning from SP3 to SP5, with SP4 between Faults C and D. Figure 4E- Annotated photo mosaic of the western half of SP5. Figure 4F- Annotated photo mosaic of the eastern half of SP5.

Package 2 Structural Data Package 3 Structural Data Package 4 Structural Data Package 5 Structural Data Poles to So, S1, and S2 F2 Fold Data F2 Fold Data Poles to So, S1, S2, and S2.5 F2 Fold Data Poles to So, S1, and S2 Poles to So, S1, and S2 F2 Fold Data N N N N Package 1 Structural Data N Station 112015-3L N N N Poles to S1 and Calculated F2 fold Axes N N Figure 4H-Slickensides.

90 270 90 270 270 90 90 90 90 180 90 270 90 270 270 270

270 90 270 90

Calculated F2 fold Axes n = 21 So n = 11 Measured So/S1 intersection lineations n = 2 So n = 8 Measured So/S1 intersection lineations n = 2 180 180 180 So n = 1 So n = 6 180 Measured So/S1 intersection lineations n = 4 180 S1 n = 20 180 Calculated So/S1 intersection lineations n = 8 270 S1 n = 84 180 Calculated So/S1 intersection lineations n = 7 Measured S1/S2 intersection lineations n = 4 S1 n = 13 S1 n = 12 Calculated So/S1 intersection lineations n = 4 S2 n = 8 Measured S1/S2 intersection lineations n = 1 S1 n = 22 S2 n = 3 Calculated S1/S2 intersection lineations n = 9 Calculated S1/S2 intersection lineations n = 10 S2 n = 12 180 S2 n = 12 Calculated S1/S2 intersection lineations n = 1 S2.5 n = 2 Calculated S1/S2 intersection lineations n = 5 Calculated F2 fold Axes n = 6 180 S1 Planes n = 2 Key: Key: S2 planes n = 2 Key: So: Blue Measured So/S1 intersection lineations: Dark Green Key: S1: SP3 So: Blue Measured So/S1 intersection lineations: Dark Green Key: Key: So: Blue Measured So/S1 intersection lineations: Dark Green Measured S1/S2 So: Blue Measured So/S1 intersection lineations: Dark Green So: Blue Measured So/S1 intersection lineations: Dark Green Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue S2: Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue intersection lineations Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue Package 1: S1: Light Green Calculated So/S1 intersection lineations: Light Blue Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink Measured S1/S2 Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink n = 1 Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink Package 2: S2: Yellow Measured S1/S2 intersection lineations: Pink Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown intersection lineaions: Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown Calculated F2 fold axes Fault C Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown Package 3: S2.5: Magenta Calculated S1/S2 intersection lineations: Brown Package 4: Calculated F2 Calculated F2 fold axes: Package 4: Calculated F2 Package 4: Calculated F2 n = 1 Package 4: Calculated F2 Package 4: Calculated F2 Package 5: fold Axes: Black Fault C Planes: Package 5: fold Axes: Black Package 5: fold Axes: Black Fault Planes n = 3 Package 5: fold Axes: Black Package 5: fold Axes: Black Fault C Slickenlines: Slickenlines n =3 Calcite slickensides along Fault C plane. Note hammer for scale SP4A Calcite slickensides along Fault B surface. Note pen for scale. Figure 5A- Stereonet of Package 1 Structural data. Figure 5B- Stereonets for Package 2 Structural data. Figure 5C- Stereonets for Package 3 structural data. Figure 5D- Station 112015-3L Figure 4G- Annotated photo mosaic of Fault C between SP3 and SP4A. Figure 5E- Stereonets for Package 4 structural data. Figure 5F- Stereonets for Package 5 structural data. stereonet.

References: Citation: Allmendinger, Rick. (2016). Stereonet 9 (Version 9.5.3) [Software].Available from http://www.geo.cornell.edu/geology/faculty/RWA/programs/stereonet.html. Chirigos, M., Kim, J., Klepeis, K., and Van Hoesen, J., 2016, Using Photogrammetry to Analyze Structures Photosynth. Microsoft, 2015; software available at https://photosynth.net. in a Tectonic Sliver in the Foot Wall of the Champlain Thrust, Shelburne, Vermont II: Vermont Geological Ratcliffe, N.M., Stanley, R.S, Gale, M.H., Thompson, P.J., and Walsh, G.J., 2011, Bedrock Geologic Survey Technical Report VGTR16-2, 1 plate. Map of Vermont: U.S. Geological Survey Scientific Investigations Map 3184, 3 sheets, scale 1:100,000.