Surficial Ge ologic M ap of the Bartle tt 7.5' Quad rangle Brian K. Fowle r 2017

Qtt EXPLANATION OF MAP Qtt Qtt Qt UNITS

Qw Qfgr Qtt Qw Swam p De p osits (Ple istoce ne > Holoce ne ) — M uck, p e at, and silty sand in p oorly d raine d locations, ge ne rally 0.3 to 1 m (1 to 6 ft) thick, and in b ank Qtt Qw locations ind istinguishab le from , grad ing into, or inte rb e d d e d with stre am alluvium . Locally p ocke te d we tland s of lim ite d are al e xte nt are ab und ant b ut not Qtt ind ivid ually m ap p e d .

Qaf Alluvial Fan De p osits, Late -Glacial, Late Wisconsinan (Ple istoce ne > Holoce ne ) — Poorly to

Qaf we ll-sorte d grave l, cob b ly till, grave lly sand , sand , and silty sand d e p osite d on slop e and ad jace nt Qfgs Qtt surface s as thin alluvial ap rons or thicke r fan-shap e d Qt Qw and te rrace d fe ature s d ownslop e from are as und e rlain b y Qt. Locally ove rlie s Qal. Qtt Qtt Qtt Stre am Channe l and Flood p lain Alluvium Qtt Qal Qtt (Ple istoce ne >Holoce ne ) — Fine to m e d ium grave l, coarse to fine sand , silty sand , silt, and occasional Qtt thin laye rs of organic d e b ris on flood p lains. Rare ly found in ste e p high-e ne rgy m ountainsid e channe ls Qtt e rod e d into clast-d om inate d till and b e d rock. Glaciofluvial De p osits, Rocky Branch V alle y, Late - Qw Qfgr Glacial, Late Wisconsinan to Re ce nt (Ple istoce ne >Holoce ne ) — Cob b ly to b ould e ry Qtt grave l d iscontinuously d e p osite d b y glacial

Qtt m e ltwate r and re d istrib ute d b y sub se que nt Holoce ne d rainage flowing south with the Rocky Branch Qw Qaf Qaf valle y. U p to 3 m (10 ft) thick and fre que ntly

Qtt ove rlain/inte rm ixe d with localize d , variab ly thick Qw d e p osits of 0.3 to 1 m (1 to 3 ft) of sand y som e tim e s Qw silty Holoce ne alluvium and sm all p ocke ts of Qw Qw Qw Qaf ve ge tate d hyd ric soils. Qw Qw Qal Qw Qt Qw Qw Qw Glaciofluvial De p osits, U p p e r Saco Rive r V alle y, Qw Qw Qfgs Qfgs Qw Late -Glacial, Late Wisconsinan (Ple istoce ne > Qw Qw Qw Holoce ne ) — Sand y to silty, cob b ly to som e tim e s Qfgs QwQw Qw b ould e ry grave l d e p osite d b y glacial m e ltwate r and Qal Qfgs Qal sub se que nt Holoce ne d rainage flowing southward Qw Qw Qw from the Crawford Notch d rainage d ivid e and ad jace nt slop e s. U p to 45 m (150 ft) thick. Qaf

Qlga Glaciolacustrine De p osits, Glacial Lake Alb any, Late -Glacial, Late Wisconsinan (Ple istoce ne >Holoce ne ) — Late -glacial, variab ly inte rb e d d e d and are ally coale sce nt d e p osits of m od e rate ly to we ll-sorte d cob b le y sand y till, cob b le y silty to sand y coarse to fine grave l, m e d ium to fine grave lly sand , and sand y silt grad e d in two Qw Qtt Qtt te rrace s to and in stage s b e low the e stim ate d m axim um wate r surface e le vation for Glacial Lake Alb any at ap p roxim ate ly 1,250 ft. De p osits he avily

Qtt d isse cte d b y the Swift Rive r and its local trib utarie s afte r d e p osition. U p to 90 ft thick and fre que ntly ove rlain b y 1 to 3 ft of Qw hyd ric soils. Qtt T ill, Late -Glacial, Late Wisconsinan (Ple istoce ne ) Qtt Qt — Ice -c ontact, ab lation and collap se -e m p lace d , locally re m ob ilize d , ofte n winnowe d , occasionally we ll-sorte d , loose to m od e rate ly com p act, b ould e ry to p e b b ly, silty to sand y, m ostly m atrix-sup p orte d d iam icton d e p osite d from glacial ice . Light to d ark Qtt grayish b rown and tan d e p e nd ing on clast p rove nance . Ge ne rally le ss than 6 m (20 ft) thick b ut !\ up to 30 m (100 ft) thick b e ne ath hillocks and rid ge - Qw like fe ature s. Clasts ge ne rally sub round e d to Qw angular and lightly to he avily we athe re d , showing a !\ m ixe d northe rly and northwe ste rly p rove nance . Qtt

Qtt re fe rs to are as whe re till is thinly d e p osite d ove r Qw Qw b e d rock. U nit includ e s local p ocke ts of b asal till on Qw Qw northwe ste rly slop e s, e sp e cially those b e low Sawye r Qt Pond .

Qtt T hin T ill — Are as whe re till is thinly d e p osite d ove r b e d rock. U nit includ e s local p ocke ts of b asal till on northwe ste rly slop e s, e sp e cially those b e low Sawye r Pond .

Water Qw Qtt Qtt Qt CORRELATION OF MAP UNITS Qw Qtt

Qw

Qtt

Qw Qtt

Qfgs Qfgs Qw

Qaf

Qw Qw Qlga Qw Qtt

Qw Qw Qw Qlga Qw !\ Text Qlga Qw Qw !\ Qw !\ Qlga

Qw Qlga Qw

Scale 1:24,000 EXPLANATION OF MAP SYMBOLS 0 1,450 2,900 5,800 Surficial Geology of the Feet !\ Photo Location 0 0.5 1 2 Well Location (Depth to Bedrock) Bartlett 7.5' Quadrangle, Miles Meltwater Channel 0 1 2 4 Surficial Ge ology b y Brian K. Fowle r Kilometers Digital Com p ilation b y Sarah W. Bake r and Gre gory A. Barke r Ne w Ham p shire State Ge ologist: Fre d e rick H. Chorm ann

Surficial Ge ologic M ap Op e n-File Se rie s GEO-065-024000-SM OF

Topographic basemap from the USGS 1998 Jefferson 7.5' quadrangle Projection: North American Datum 1983 New Hampshire State Plane Feet. This geologic map was funded in part by the CRAWFORD NOTCH STAIRS MOUNTAIN JACKSON 1000 meter grid in UTM zone 19 North, Contour Interval 6 m USGS National Cooperative Geologic Mapping Program Hillshade produced from high resolution (1 meter and 10 meter) LiDAR data under StateMap award number G16AC00299

NHGS Open-File Disclaimer: This map and the accompanying legend(s) are understood to be New Hampshire Geological Survey BARTLETT NORTH CONWAY WEST open-file products. They are draft versions of an unpublished report and represent mapping NH Department of Environmental Services progress at the time of completion. Newer information may exist. If you have questions, please 29 Hazen Drive, P.O. Box 95 contact the New Hampshire Geological Survey (NHGS) at: [email protected] or (603) 271-1976 Concord, NH 03302-0095 Phone: 603-271-1976 E-mail: [email protected]

MOUNT TRIPYRAMID MOUNT CHOCORUA SILVER LAKE Bartlett 7.5 Quadrangle

Explanation & Description

Qw: Swamp Deposits (Pleistocene>Holocene)

Muck, peat, and silty sand in poorly drained locations, generally 0.3 to 1 m (1 to 6 ft) thick, and in bank locations indistinguishable from, grading into, or interbedded with stream alluvium. Locally pocketed wetlands of limited areal extent are abundant but not individually mapped.

Qal: Stream Channel and Floodplain Alluvium (Pleistocene>Holocene)

Fine to medium gravel, coarse to fine sand, silty sand, silt, and occasional thin layers of organic debris on floodplains. Rarely found in steep high-energy mountainside channels eroded into clast-dominated till and bedrock.

Qaf: Alluvial Fan Deposits, Late-Glacial, Late Wisconsinan (Pleistocene > Holocene)

Poorly to well-sorted gravel, cobbly till, gravelly sand, sand, and silty sand deposited on slope and adjacent surfaces as thin alluvial aprons or thicker fan-shaped and terraced features downslope from areas underlain by Qt. Locally overlies Qal.

Qlga: Glaciolacustrine Deposits, Glacial Lake Albany, Late-Glacial, Late Wisconsinan (Pleistocene>Holocene)

Late-glacial, variably interbedded and areally coalescent deposits of moderately to well-sorted cobbly sandy till, cobbly silty to sandy coarse to fine gravel, medium to fine gravelly sand, and sandy silt graded in two terraces to and in stages below the estimated maximum water surface elevation for Glacial Lake Albany at approximately 1,250 ft. Deposits heavily dissected by the Swift River and its local tributaries after deposition. Up to 90 ft thick and frequently overlain by 1 to 3 ft of Qw hydric soils.

Qfgs: Glaciofluvial Deposits, Upper Valley, Late-Glacial, Late Wisconsinan (Pleistocene > Holocene)

Sandy to silty, cobbly to sometimes bouldery gravel deposited by glacial meltwater and subsequent Holocene drainage flowing southward from the Crawford Notch drainage divide and adjacent slopes. Up to 45 m (150 ft) thick.

Unit Descriptions & Map Notes Page 2

Qfgr: Glaciofluvial Deposits, Rocky Branch Valley, Late-Glacial, Late Wisconsinan to Recent (Pleistocene>Holocene)

Cobbly to bouldery gravel discontinuously deposited by glacial meltwater and redistributed by subsequent Holocene drainage flowing south with the Rocky Branch valley. Up to 3 m (10 ft) thick and frequently overlain/intermixed with localized, variably thick deposits of 0.3 to 1 m (1 to 3 ft) of sandy sometimes silty Holocene alluvium and small pockets of vegetated hydric soils.

Qt & Qtt: Till, Late-Glacial, Late Wisconsinan (Pleistocene)

Ice-contact, ablation and collapse-emplaced, locally remobilized, often winnowed, occasionally well-sorted, loose to moderately compact, bouldery to pebbly, silty to sandy, mostly matrix- supported diamicton deposited from glacial ice. Light to dark grayish brown and tan depending on clast provenance. Generally less than 6 m (20 ft) thick but up to 30 m (100 ft) thick beneath hillocks and ridge-like features. Clasts generally subrounded to angular and lightly to heavily weathered, showing a mixed northerly and northwesterly provenance. Qtt refers to areas where till is thinly deposited over bedrock. Unit includes local pockets of basal till on northwesterly slopes, especially those below Sawyer Pond.

General Map Notes, Specialized Symbols

Artificial Fill: Manmade fills and various sorts of surface alteration along and adjacent to the Quadrangle’s road network and developed areas are not separately shown for clear depiction of underlying and adjacent units. Map Symbols

Boundary Between Surficial Geologic Units: all are approximate or ------inferred due to often inaccessible terrain, dense vegetation, varying and poor exposures. Well Data w/ (Depth To Bedrock); (xxx) NH Dept. Environmental Services (NHDES) NH Geological Survey (NHGS)

(hachure) Areas of Extensive Bedrock Outcrop

>>>>>>>>> Abandoned Meltwater Channel (Falls Pond @ Rocky Gorge, Upper Falls

Unit Descriptions & Map Notes Page 3

Selected References

Fowler, 2011, Surficial Geology of and the , New Hampshire, 2010. Durand Press, Lyme, NH (annotated map, 1/24,000).

Henderson, D.M., Billings, M.P., Creasy, J., and Wood, S.A., 1977, Geology of the Crawford Notch Quadrangle, New Hampshire. NH Dept. Resources & Economic Development, 29 p. with map.

Koe, Sarah G., 2016, Applications of LiDAR in the study of landscape geomorphology, , White Mountain National Forest. Standard Senior Thesis, Bates College, Lewiston, ME.

Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, J.B., 1997, Bedrock geologic map of New Hampshire. U.S. & N.H. Geological Surveys. Map and structure sections.

Nelson, A.E. and Goldsmith, R., 2000, Surficial Geologic Map, North Conway West Quadrangle. U.S. & N.H. Geological Surveys. One Sheet.

Thompson, W.B., Fowler, B.K., and Dorion, C.C., 1999, Deglaciation of the northwestern White Mountains, New Hampshire. Geographie Physique et Quaternaire, v. 53, no. 1, p. 59-77.

Surficial Geology of the Bartlett 7.5-minute Quadrangle

This reconnaissance-level mapping shows that the features of the quadrangle’s surficial geology resulted first from erosion associated with continental glaciation during the Late Wisconsinan Glacial Stage, the last to affect the region, followed by deposition, erosion, and redeposition that took place as this thick ice sheet downwasted across the region.

The region's more gradual northwesterly slopes and steeper southeasterly slopes, along with several areas of glacially streamlined topography, indicate that the ice sheet generally flowed over the region from the northwest. No glacial striations were observed due to the rapidly weathering surfaces of the locally predominant granitic bedrock.

Erosion associated with this glacial movement affected the quadrangle’s topography by rounding and smoothing its peaks and by steepening southeast-facing slopes through the process of “plucking” (stoss and lee topography). No systematic terminal or recessional moraines were located and this, in combination with the location and nature of post-glacial deposits, shows that the ice sheet did not retreat from the region but instead rapidly downwasted in place, first thinning over higher areas and then separating around them. This process stranded locally wasting masses of glacial ice from which thick deposits of ablation till collapsed onto, and were then redistributed upon, newly exposed bedrock surfaces (Qt & Qtt). Much of this ablation till was then heavily winnowed and redeposited by surficial meltwater. Limited exposures of basal till are present on northwest-facing slopes, but are missing at the surface elsewhere in the quadrangle, having been most likely buried by the collapse of ablation till.

Systematic fluvial deposition is restricted to the Saco River valley where two stages of such deposition exist. The first is represented by poorly to moderately well-sorted outwash deposits (Qfgs) on the floor of Unit Descriptions & Map Notes Page 4 the upper valley that resulted from heavily sediment-laden discharge flowing out of Crawford Notch above, while the second is represented by the sandy gravel and sand alluvium on the river’s floodplain in the central and eastern parts of the quadrangle. In addition, the continuing entrainment of coarse to medium sediment from tributary valleys into the Saco Valley is evidenced by the presence of alluvial fans of poorly-stratified gravelly till that overlie both these types of fluvial deposits.

Two locations of special interest include the immediate vicinities of Swift River basin and the Sawyer Pond basin located, respectively, in the southeastern corner and on the central western margin of the quadrangle.

The Swift River Basin provides an interesting chronology of deglaciation. Initially, meltwater from downwasting ice in this valley appears to have drained south out of the basin over two cols and into the Kelley and Paugus Brook valleys (on the Mt. Chocorua 7.5-minute quadrangle). This initial stage involved meltwater flowing to the south off the surface of a thick, rapidly wasting and separating ice mass located within the broad basin between the combined mountain slopes of Table and Bear Mountains, Mt. Tremont, and Owl Cliff to the north and the confining mountain ridge of Mounts Tripyramid, Passaconaway, and Paugus to the south (on the Mt. Chocorua 7.5-minute quadrangle). Evidence of this initial stage lies in and below the high cols on this southerly ridge and consists of deeply incised stream channels and apparent thick sediments. As the ice melting progressed and ice mass drew back within the basin, successive ponding is apparent within the Swift River basin as evidenced by terrace features at lower elevations within Sabbaday Brook, Downes Brook and Oliverian Brook (Koe, 2016). These features originated as pockets of trapped sediment in ponded water between the ice mass within the valley and the north facing mountain slopes and record an intermediate evolution of ponded meltwaters and lowering of the ice margin within the basin. As melting progressed and the lake basin finally became ice- free, several intermediate and localized higher elevation water surfaces were created that quickly lowered to a stabilized elevation behind a cross-valley morainal “plug” at an elevation of about 1,250 feet at the present location of the Upper Falls/Falls Pond area. There are several abandoned and progressively lower and heavily eroded channels at this location, the highest of which is at an elevation of 1625 feet which is more than 375 feet above the current bedrock threshold (including Falls Pond itself). From this evidence, the lake is interpreted to have drained in several stages until the plug was completely breached and the Swift River began dissection of the residual lake-bottom deposits on the relatively flat floor of the basin that now forms the “Albany Intervale”, traversed today by the Kancamagus Highway.

The second location of special interest is the basin of Sawyer Pond, a +/- 40-acre body of water surrounded by higher mountain terrain uniformly covered by very thick deposits of bouldery ablation till (no bedrock outcrops observed). Bathymetry in the pond shows it is very deep (average 47 ft; maximum 90 ft) despite its limited areal extent. Given its location in a basin comprised completely of ablation till, it seems likely the pond occupies a void created by the melting of a very large mass of wasting glacial ice that was isolated in the mountain basin by the surrounding topography. As this ice mass melted, ablation debris that had earlier collapsed around it slumped into the expanding void, ultimately creating the small but exceedingly deep lake present today. Unit Descriptions & Map Notes Page 5

Figure 1 View From Sawyer Pond looking at Owls Cliff Unit Descriptions & Map Notes Page 6

Figure 2 View from Crest of Bear Notch looking north at the Saco River Valley and the Presidential Range

Figure 3 View at Rocky Gorge on the Swift River, just below the outlet for Glacial Lake Albany Unit Descriptions & Map Notes Page 7

Figure 4 View of glacial meltwater channel, at left in photo, just above Falls Pond. Meltwater moved from the bottom left corner of the photo over the crest in the distance and down to the Falls Pond area.

Figure 5 View from Falls Pond. The glacial meltwater channel depicted in Figure 4 drains to the notch in the tree line at the center of the photo. Unit Descriptions & Map Notes Page 8

Figure 6 View of a Glacial Lake Albany terrace deposit. This photo was taken from off the quadrangle and faces north. Owls Cliff, at left, and Bear Mountain, at right, create the skyline in the background.