A3: GLACIAL REGIME AND DEPOSITIONAL ENVIRONMENTS ALONG THE RETREATING LAURENTIDE ICE SHEET, NORTHEASTERN APPALACHIAN PLATEAU, NEW YORK
P. Jay Fleisher
Earth Sciences Department
SUNY-Oneonta
ABSTRACT
Deglacial environments along the retreating Laurentide Ice Sheet throughout of the upper Susquehanna region were primarily controlled by an ice front configuration draped across the high relief, Appalachian Plateau terrain. Valley ice tongues extended 20 km beyond upland positions commonly terminated in ice-contact lakes. Active ice flow nourished by the ice sheet persisted within through valleys, where as ice tongues in non-through valleys became detached and stagnated. Temperate conditions and hydrologic connection with the ice sheet supported highly turbid englacial and subglacial tunnel discharge directly into through valley ice-contact lakes. Subaerial streams favoring positions lateral to ice tongues transported sand and gravel outwash to prograding deltas. Thus, bottomset and toeset sediments interfinger with lacustrine silt and sand. Post-glacial dam incision followed by lake emptying led to the modern landscape. A finer facies of thick silt and sand lies beneath the modern floodplain and is typically bound by deltaic terraces (commonly called kame terraces) consisting of the coarser facies sand and gravel.
In contrast, downwasting over non-through valley headward divides led to loss of nourishment and near separation of the ice tongue from the ice sheet, thus causing the combined effect of hydrologic disconnection and stagnation. Consequently, non-through valley environments of deposition were less uniform, characterized by a) local pending behind ephemeral ice-cored dams, b) kilometer-size, detached ice masses partially covered by outwash and lake sediments, and c) meltwater sources limited to the volume of the detached ice tongue. These collectively describe an environment significantly different from through valleys. Non-through valley sediments are far more diverse, less well sorted, and lack the laterally uniform subsurface conditions characteristic of through valleys. In addition, the landform assemble also differs through the lack of a continuous lacustrine plain, segmented terraces graded to local base levels, isolated small esker-forms, kame and kettle topography unrelated to systematic moraines (called kame fields), and mega-kettles that span the valley floor (known as dead ice sinks).
The Bering Glacier, Alaska, depicting sedimentary conditions in ice-contact lakes and along peripheral drainage systems is cited as an analog for the retreating Laurentide Ice Sheet in central New York.

A3: Glacial regime and depositional environments along the retreating Laurentide Ice Sheet, northeastern Appalachian Plateau, New York

I-88 parallels the Susquehanna River for the next 2.4 miles.
Active floodplain aggradation mantles lake sediments of Glacial Lake Otego that was dammed during retreat by the Wells Bridge Moraine, our first stop.

Good view of the modern flood plain and change in valley trend
The highway rises above the valley floor and provides a good view of the modern flood plain and the abrupt change in valley trend that is a remnant of a preglacial ingrown meander. A bedrock promontory on the horizon to the right (north) protrudes into the valley along the inside of the meander bend.

Stop 3 is on the left (south), but we won't stop now.
Access to this area is possible from County Rd. 48 (locally referred to as the Otego-Wells Bridge Rd.), which we will take on our return to the Oneonta area from Wells Bridge.

Continue west on I-88 past Rt. 7 & Otego exit.

View to the west of valley plug formed by the Wells Bridge Moraine.

Back of the Wells Bridge Moraine and an associated kame terrace.
View to the right (north) across the valley includes the back of the Wells Bridge Moraine and an associated kame terrace. The next 1.2 miles provides excellent overviews of the moraine and the gap cut by the Susquehanna River.

STOP 1. Wells Bridge Moraine (Franklin and Unadilla Quadrangles).
The hummocky relief of this moraine is common for other moraines in the upper Susquehanna drainage basin. This moraine completely blocked the valley following glacier retreat thus forming the dam for Glacial Lake Otego that extended about 25 km upvalley to Oneonta. Logs of water wells from the floor of the valley penetrate more than 400 feet of silt without encountering bedrock. Rates of sedimentation from similar ice-contact lakes at Bering Glacier, Alaska, related to vertical settling of suspended sediment between 0.6 and 1.2 m/yr. Therefore, Glacial Lake Otego may have been relatively short-lived.
The configuration of the Laurentide ice front during retreat is commonly thought to have consisted of valley ice tongues. Early work portrayed relatively short ice tongues, where as more recent evidence suggests that they may have reached 20 km in length. This raises implications of sediment source areas and transport mechanisms, while opening the topic of mechanisms of moraine formation. Considering that most moraines in the region consist of stratified drift and lack topographic expression other than in valleys, alternatives to conventional moraine formation may be entertained.
The Wells Bridge Moraine is assumed to have been emplaced about 15,000 years BP and breached about 14,000 years BP. We will consider the field evidence for an 1140 feet lake level at stop 3. Field work in the Unadilla and Sidney areas indicates that the Upper Susquehanna Lake Chain has greater downvalley extent than will be covered in this road log.

Cross Ouleout Creek.

Highway parallels the river for one mile.

Highway climbs onto outwash terrace near mouth of Sand Hill Creek.

Highway drops into Sand Hill Creek incision of outwash
Highway drops into Sand Hill Creek incision of outwash and immediately climbs to follow the contact of the Wells Bridge Moraine and outwash.

Crest of moraine on the left, breach on the right.
It was within the breach of this moraine that archeological excavations uncovered charcoal in silt covering a buried river point bar. This was dated at 13,000 to 14,500 years BP, thus providing limiting age of Lake Otego.

Road parallels river for 0.6 miles before rising onto an outwash terrace.
A correlative terrace can be seen across the valley to the north at an elevation of about 1140 feet.

Suggest a second level for Lake Otego below 1140 feet.
White house across the valley to the north is situated on a terrace at about 1120 feet. Other planar landforms can be found along the valley that suggest a second level for Lake Otego below 1140 feet.

STOP 2.
Massive red sandstone outcrop on south side of parking lot is covered with glacial abrasional features on joint faces that parallel the valley wall. Note that striae and grooves are inclined in the downvalley direction, thus indicating topographically controlled ice flow consistent with valley ice tongue model. Basal flow of overriding ice would not have produced such features. Several joint block surfaces that do not parallel the valley trend are also polished, but not by ice flow. These very smooth and polished surfaces are the product of abrasion by highly turbid water flow and support the notion of a highly charged subglacial hydrologic system.

Gravel excavation on right contained deltaic foreset and topset beds
Gravel excavation on right contained deltaic foreset and topset beds indicating a downvalley current direction.

Gravel excavation on left contained deltaic foreset and topset beds
Gravel excavation on left contained deltaic foreset and topset beds indicating a downvalley current direction.

Road drops to modern flood plain
Road drops to modern flood plain, which is superimposed on Lake Otego lacustrine plain. Lacustrine plain continues to the left and right.

Kame on the right.
Prior to construction of I-88 a bit smaller feature could also be seen to the northeast.

STOP 3.
Park on the right beyond the overpass and walk south between I-88 and the forested slope. About 300 meters south of overpass and upslope from the fence, at an elevation of approximately 1120-1140 feet (2/3 the way up the forest-free slope), pebbly coarse sand, fine sand, silt, and a few clay seams were exposed during construction. Fluvial channel structures with small scale foreset beds inclined into the slope and down valley rested upon finely laminated, rippled and cross bedded silt and fine sand. These sands are interpreted to have formed along the strandline of Lake Otego by wave generated currents that moved into this valley wall alcove. The sand about 1140 feet lacks pebbles, is considered to be of eolian origin, blown up slope from the beach.

Road drops back down to the lacustrine plain at an elevation of 1,060 feet.

The highway traverses an outwash/alluvial bench
The highway traverses an outwash/alluvial bench between 1100 and 1120 feet at the confluence of Otego Creek and the Susquehanna River.

Dead-ice sink on right

Unadilla River

STOP 4.
Through valley landforms (New Berlin South Quadrangle)- high terrace (1180') consisting of deltaic valley train marking the ice margin (no moraine) at the head of which is a dead-ice sink. Although excavation in this quarry has been inactive for several years, large-scale, deltaic foresets are still expressed through the colluvium. The nearest base level to which these deposits may be graded is 22 km downvalley at Rock Wells Mills (Guilford Quadrangle), where kame and kettle, morainic topography may have served as a drainage plug in a constricted segment of the valley. A partially preserved hummocky, kame terrace at White Store (16 km downvalley) also suggests ice burial.
Earlier exposures here included interbedded, very coarse, clast supported boulder gravel and pebbly, coarse sand. A carbonate cement in some units is related to limestone clast weathering, leaching, and reprecipitation at depth, thus indicating the "bright" nature of this outwash.
The Unadilla River is incised within a valley train and flows from a dead-ice sink upvalley to a lacustrine plain downvalley. These landforms and their internal features are indicative of active ice retreat with glaciofluvial sediment transport into an ice-contact lake. Partial burial of a detached, large remnant ice mass caused retarded melting until after meltwater sedimentation ceased, thus allowing collapse and topographic preservation of a dead-ice sink. Water well logs within the sink verify the lack of subsurface, stratigraphic continuity.

Road rises on gravel terrace above lacustrine plain

A high-level terrace at 1280' to 1300' on west side of valley
A high-level terrace at 1280' to 1300' on west side of valley continues for 1.5 miles west of South Edmeston. It appears to be an older kame terrace with no apparent downvalley base level, thus suggesting ice served that purpose.

Road rises on pitted planar gravel and kame field

Inwash sediment source and topographic expression of kame field, Columbus Quarter (New Berlin North Quadrangle). The kame field and associated pitted plain may have served as a local, temporary dam (1220') for a lake upvalley. Pebble counts from upland "drab" drift now resting on the "bright" drift of the kame field suggest tributary inwash from Tallette Creek as a source of sediment (see plot of pebble count data, after Yuchniewicz, 1996).

Proceed east across lacustrine plain.

Road descends onto the pitted and discontinuous valley train of Butternut Creek.

Road descends onto the kame and kettle topography of the Oaksville Moraine.

Road crosses the crest of the moraine
Road crosses the crest of the moraine and continues on and off the moraine for next 1.5 miles through the villages of Oaksville and Fly Creek.

Quarry operation in sand and gravel valley train
Quarry operation in sand and gravel valley train with classic assemblage of glaciofluvial sedimentary structures on the left (east). The road continues along the floor of a dead-ice sink

STOP 6. Cassville-Cooperstown moraine, at Index
(5 km south of Cooperstown) (Cooperstown Quadrangle).
This classic through valley landform assemblage (a moraine linked with an extensive valley train) represents active ice deposition. Old excavations in a nearby borrow pit exposed stratified sand and gravel. Test borings indicate that the gravel of the moraine interfingers with silt upvalley, toward Cooperstown, before yielding entirely to silt (120+ feet thick, Fleisher, 1992). The classic kame and kettle expression of this moraine loses all topographic expression as it rises to the uplands, as is characteristic of moraines in central New York State. This has implications for a moraine forming mechanism that would involve sediment transport dominated by glaciofluvial processes.
Based on topographic criteria, Krall (1977) correlates the Cassville-Cooperstown Moraine with moraines in the Hudson Valley, thereby suggesting a readvance circa 14,000 years BP. Ridge, et al., (1991) makes a tentative correlation with the West Canada Readvance of late Wisconsinan, pre-Valley Heads age (circa 15.5 ka) based on elevation projections of ice-marginal deposits in the Mohawk Valley and the limit of readvance inferred from subsurface stratigraphy (Fleisher, 1986).
Although high enough, this moraine did not dam Glacial Lake Cooperstown, although landforms and stratigraphy suggest that a proto-Lake Cooperstown may have extended to the moraine by "swamping" a dead-ice sink.

Dead-ice sink
Dead-ice sink between Cassville-Cooperstown Moraine and Cooperstown occupies the valley floor for the next mile.

STOP 7. Lake Front Park on Doubleday Ice Margin
Well data from the crest of the moraine (Bassett Hospital) indicate that the morainic dam for Otsego Lake consists of 180 feet of bouldery silt. Subtle hummocky terrain in the village of Cooperstown may be traced northwestward, where it is well expressed in a golf course at the lake shore. Hanging deltas along the western lake shore and lake clay on the northwestern shore indicate that while the moraine dammed Glacial Lake Cooperstown at an elevation of 1250'. The view northward includes a conspicuous cross-sectional valley asymmetry, which played an important role in determining the primary sediment source for Glacial Lake Cooperstown.
A seismic reflection survey shows that Otsego Lake occupies a rock basin that has been eroded as much as 132 m (433') lower than present lake level and infilled with up to 88 m (289') of sediment. Sediment thickness is greatest in the southern half of the lake basin and thins by -50% to the north where maximum water depths occur. As an alternative to the traditional view of deglaciation, which depicts continuous backwasting of an active ice margin with short valley lobes, subsurface and land-based evidence suggests backwasting retreat of 20 km long ice-tongues that remained in the valleys, subject to collapse while adjacent upland regions were ice-free. Proglacial sediments were largely transported to the south end of the lake basin as alluvium from ice-free western tributary streams (Fleisher, et al., 1992).

Highway traverses Cassville-Cooperstown moraine.

From here south for several miles, planar gravels
from here south for several miles, planar gravels appear related to upland tributary inwash sources.

Valley floor consists of lacustrine clays
Valley floor consists of lacustrine clays from here south to a moraine at Portlandville at 68.9.

STOP 8. Goodyear Lake overview at Milford Center
Pitted valley train and dead-ice sink. These landforms indicate local stagnation of the valley ice-tongue during active retreat. However, the valley fill consists of 60+ ft. of ice-contact, sand and gravel outwash over 300+ ft. of silt interpreted to be of lacustrine origin. Does the stratigraphy indicate two stades (readvance) or is there a single-stade environment that accounts for both stratigraphic units? Aggradation over ground ice islands is suggested.

Dead-ice sink right and left.

STOP 9. Moraine at margin of Dead Ice Sink
Approval for entrance to quarry must be obtained in Office.
Many of the landforms that characterize the through valley assemblage may be found in the vicinity of this location. They include a kame moraine and associated outwash features, dead ice sink, and lacustrine plain. During the many years of operation, a variety of ice-contact features have been exposed. Upper-most units are flow tills (debris flows) that randomly interfinger with interbedded sand and medium gravel, frequently including silt and sand of local significance. Blocks of lodgment till have been observed in piles with sub-meter boulders that come off screening equipment. Massive foreset beds of gravel that range in size from bouldery gravel, through cobble and pebble gravel, to pebbly, course sand are commonly found beneath the overlying flow till at an intermediate, vertical position through the operation. Well sorted, laminated lake sand is very common on the downvalley, lower margin of the quarry.
The hummocky, kame and kettle topography common to the quarry area fades downvalley to join with the surface of extensively developed outwash terraces. Over the years, quarry operations in these terraces have uniformly exposed massive gravel foreset beds indicative of meltwater sedimentation in an ice-contact lake that expanded upvalley to follow the retreating ice front. MacNish and Randell (1982) describe such a setting to depict slow, active-ice retreat.
These extensive paired terraces formed as "lateral deltas" into the expanding ice-contact lake, thus growing in the upvalley direction as space became available during retreat. Episodes of slow retreat would accommodate growth until delta terraces from either side of the valley coalesced to fill the valley, thus forming a valley train with internal deltaic structure.

Entrance to Brae Pit, Cobbelskill Products quarry.
Time permitting, we will drive in to view massive foresets of delta terrace.

Road parallels Charlotte Creek through the moraine on the right.

STOP 10. Davenport Center. Pine Lake Dead-ice Sink Complex.
These kames and sinks formed in an ice-cored terrain at the mouth of Charlotte Creek where this transverse valley was clogged by remnant ice. These landforms are typical of valleys in which the stagnated ice was subject to inwash burial and many local ponds and lakes existed. Here, the Davenport Moraine dammed Charlotte Creek valley at 1280 ft. Many shoreline landforms along the valley are graded to this lake.

Right hand fork goes downhill and across the lacustrine plain of Glacial Lake Davenport.

Town of Davenport Center quarry on right
Town of Davenport Center quarry on right (no longer active). Past exposures contained well-developed, large-scale deltaic foreset beds graded to 1280 ft. water level. Forty foot deep kettles indicate progradation that incorporated grounded ice.

STOP 11. Hanging delta at the confluence with Middle Brook
Clark Company Stone Products. Although quarrying activity continues, much of this original hanging delta into Glacial Lake Devenport (1280 to 1300 ft.) has been excavated. Remnants of evidence supporting this interpretation may still be seen. Exposed at the upper quarry level are several meters of well stratified, strongly imbricated topset gravel. Discontinuous exposure to lower positions eventually lead to multiple packages of lacustrine sand and silt interspersed with small-scale deltaic infill and cut and fill structures.

Stop 12. Very localized hummocky topography reaching elevations of 1360 ft.
Turn right on Olive Branch Road (Dead End) at Brandow's Trailer Sales. Access by permission of Brandow Family.
Recent excavations exposed several, 2-3 m thick, alternating units of cross bedded coarse sand, tan laminated lake sand, and sand and fine gravel, each with unconformable contacts. The entire sequence was overlain by 2-3 m of moderately well sorted pebble gravel. Isolated from potential tributary sources, this ice-contact landform appears to have originated as meltwater infill of localized ponding on ice-cored terrain, much as would be anticipated in contact with a remnant ice masses in a transverse valley.

Highway traverses moraine at West Davenport.

Terrain to the left is what may be the only lateral moraine in this area.

Road descends to Susquehanna valley lacustrine plain.

Highway enters the breach of the Oneonta Moraine (significantly altered by urban development).

OPTIONAL STOP 1. Village of Laurens Quarry
This is a good example of inwash sourced aggradation associated with a stagnant, downwasting ice tongue that occupied this non-through valley and other like it. At various times, excavation has exposed tilted and truncated sequences of interstratified gravel and pebbly sand with fluvial sedimentary structures and local silt layers of lacustrine origin. The basic feature is an ice-contact, hanging delta (Mt. Vision Quadrangle). Landform expression and large-scale foreset and topset beds indicate deposition into an ice-contact lake. Initial aggradation here was into a lake graded to a moraine dam at West Oneonta, 5 km downvalley. A local inwash source provided adequate sediment for additional topset, alluvial aggradation above lake level.
Otego Creek passes through a narrow breach that interrupts the continuation of this landform at the same elevation across the valley floor. The localized concentration of accumulated sediment here is attributed to inwash from Lake Brook. Similarly, other tributaries fed sediment from ice-free slope to local lakes and ponds distributed along the valley and gravel plains are graded to these water bodies.

Gravel plain remnant for next half mile.

Road rises onto pitted planar gravel remnant.

Road traverses terrain of ice-cored origin
Road traverses terrain of ice-cored origin including a small esker out of sight to the right.

OPTIONAL STOP 2. Esker in dead-ice terrain
Once again we see concentrated aggradation at a stream confluence, here where West Branch joins Otego Creek. Landforms typical of a non-through valley assemblage include a kame field (differs from a kame moraine only in that the kame and kettle topography is not linked with planar outwash, as would be anticipated at an active ice margin), gravel plain, dead-ice sink, and an esker. Eskers are rarely preserved, partly because conditions favoring formation were not common, but also because they are excellent sources of sand and gravel, thus they are typically removed by gravel mining. Here, the esker is indicative of stagnant ice conditions. Lack of excavation precludes investigation of internal features.

Turn right onto Angel Road that traverses kame field.

OPTIONAL STOP 3. Overview of meltwater channel
Overview of meltwater channel through discontinuous gravel plain remnant and terrain of ice-cored origin.

Road descends to a local lacustrine plain (dead-ice sink?)

Gravel excavation to the left removed a landform thought to be an esker.

OPTIONAL STOP 4.
Overview of discontinuous, planar gravel surface and terrain of ice-cored origin bordering a local, upvalley lacustrine plain.

OPTIONAL STOP 5. Overview of headward area in non-through valley.
Valley floor contains a few isolated kames. Unlike through valleys, the valley floor gradually rises to upland slopes across which ice flow diminished due to thinning during glacial retreat, thus resulting in downvalley ice-tongue starvation and ultimate stagnation.