Abstract

The Butternut Valley in the Appalachian Plateau of upstate New

York hosts a considerable number of alluvial fans abutting the

valley walls and resting at the mouths of several small tributaries

to the Butternut Creek, which is a headwaters drainage to the

Susquehanna River. These fans were deposited during a time

period ranging from deglaciation to ice free conditions. Ice-

contact and post-glacial deposits rest in close contact with each

other. We hypothesize that the distribution of post-glacial fans

varies between valley types in this area. Basically, valleys that

served as outlets for ice streams from the Laurentide ice sheet

(through valleys) experienced active ice conditions, whereas non-

through valleys experienced stagnant ice conditions. In both

cases, exposed upland tributaries delivered sediment into the main

valleys which were still occupied by glaciers. Within non-through

valleys, alluvial fans experienced deposition against or on

stagnant (dead) ice. We propose that fan formation is most

common within non-through valleys as opposed to through-

valleys, due to greater degree of sediment mobility in through

valleys from active ice and increased meltwater.

We present herein new mapping of alluvial fans in a non-through

valley setting. Ice contact fans exhibit toes with sharp or distinct

angles of repose and an uneven undulating appearance from on-

ice deposition. Fans deposited after ice retreat retain a classic fan

semblance marked by a nearly linear profile and radial

distribution pattern. At many tributaries we find a series of fans

which provide a history of deposition during deglaciation. Ice

contact fans are typically higher in elevation than younger fans.

We are beginning to more formally interpret fan distribution and

areal extent using digital topographic data (USGS National

Elevation Data), new LiDAR elevation data for parts of our field

area, and field mapping.

MAPPING AND CHARACTERIZING LATE GLACIAL AND HOLOCENE ALLUVIAL FANS IN UPSTATE

NEW YORKKAKOLEWSKI, Christopher and HASBARGEN, Les, Department of Earth Sciences, SUNY College at Oneonta, Oneonta, NY 13820-4015, ckakolewski@gmail.com

Session No. 81--Booth# 60

Recent Advances in

Understanding the

Geomorphology and Quaternary

History of the Appalachian

Region and Adjacent Regions

Sheraton Baltimore City Center:

International ABCDF

Tuesday, 16 March 2010

Geological Society of America Abstracts with Programs, Vol. 42, No. 1, p. 189

Fan Identification Criteria:

Glaciology and Geomorphology:

Summary of Methods and Limitations:

Alluvial Fan Profiles:

Figures 1a and 1b: Map of New York State illustrating the location of the Butternut Valley and the Butternut Valley highlighted in black rectangle.

Figures 2a and 2b: National Elevation Dataset (NED) 1/3 arc second (10 meter resolution) maps of the Butternut Valley highlighting drainage basins (black comb) and alluvial fans (black dots) . Both figures use slope shading, although, figure 2a highlights slopes from 0-3

degrees while figure 2b highlights slopes from 0-10 degrees. Yellow indicates lower slope values while blue indicates higher values. Each setting can help to elucidate fan features.

Figure 3: Digital Raster Graphic (DRG) 1:24,000 scale map (2.438 meter resolution) providing contour and topographic surface details.

Figures 4: National Agricultural Imagery Program (NAIP) image of Wheeler Fans (Kakolewski and Hasbargen, 2009) (one meter

ground sample distance and six meter accuracy) with superimposed GPS points correlating to specific data collection sites.

Figure 5: Line of site profile (Wheeler Fans Fig. 4) highlighting from left to right an abutting

fan surface. The first yellow point represents the current depositional fan surface. The next

point features the intermediate age fan surface. The undulating character of the intermediate

fan suggests deposition on ice. The third point represents a channel below a sharp angle of

repose leading to a third, ice contact, fan surface.

Figure 7: Map outlining alluvial fans and drainage basins. Blue represents drainage basins, red indicates alluvial fans, and green indicates fans abutted

against ice.

Graph 1 and 2: Graph 1 shows that there is a very weak correlation between fan area and basin area in a through valley

setting. Graph 2 however shows a much stronger correlation between fan size and drainage basin size. The correlation can

probably be strengthened by more thorough mapping through LiDAR, especially in non-through valleys, and extrapolating

where fan surfaces would be if they were not affected by floodplains. The power law suggests that there is a stronger

correlation between fan areas and basin areas in non-through valley settings as opposed to through valley settings which can

be a general way to discriminate between in through and non-through valleys.

Table 1: Statistical slope data for the

20 fans mapped in the vicinity of

Butternut Valley

Average slope, degrees1.8

Standard Deviation 0.7

Variance 0.5

Skew 0.1

Max 2.99

Min 0.54

Range 2.45

Occurs at the mouth of a tributary.

Exhibits radial shape.

Average linear slope approximately near 0 and 3 .

Undulating surface indicate on-ice deposition.

Sharp angles of repose along fan margin indicates ice contact

deposition.

Radial shape and smooth linear slope relates to post glacial

deposition.

Fans push trunk stream channel to far side of the valley.

Lithology and stratigraphy.

Alluvial fan area versus the drainage basin area can

distinguish between fans that are part of a through valley or a

non –through valley setting.

Four main tools were used in the identification of alluvial fans in the non and

through valley setting; National Elevation Dataset (NED, 1/3 spacing), Digital

Raster Graphics (DRG 1:24K topographic quadrants), National Agricultural

Imagery Program (NAIP air photos), and field mapping. Each of the three data

sets contributed to the characterization of fan surfaces by elucidating their shape

and areal extent. Slopes were highlighted in the 0 to 3 and 0 to 10 range on

the NED to quickly locate areas of potential fan locations. The DRG 24K map

provided contours which show radial shapes. NAIP images provide a

visualization of vegetation, surface shadows, and color that computer or hand

drawn maps cannot virtually display. We mapped the margins of some alluvial

fans (marked as a distinct contact where fan gravels pinched out over the

modern fine-grained floodplain) with a GPS unit. This was then superimposed

on a map with Globabl Mapper ® software.

Each of these tools are limited by accuracy of available data. NED, DRG,

NAIP, and GPS range between several and many meters of accuracy. The

resolution displayed by these maps decreases as areas of interest are refined to

smaller sizes. LiDAR data sets can be used to improve resolution to a 1 meter

scale, however, LiDAR files are very large and typical computers are often not

powerful enough to handle them. In addition, the extent of LiDAR scans is

limited.

Figure 6: LiDAR map of alluvial fan west of the Butternut Valley – 5m resolution.

Through Valley – A valley in which glaciers passed through with no

identifiable origination point. Through valleys tend to experience

higher runoff and erosion rates and less stagnant ice features.

Non-Through Valley – A valley in which glaciers had a clear

origination point and generally connects to a through valley. These

valleys often exhibit a high degree of stagnant ice features such as

undulated surfaces, kettles, sinks, and well formed alluvial fans that

can exhibit a terraced surface due to direct ice contact formation.

Many glacial features can be recognized from the data sets.

Ridges running along valley walls are often kames while mounds

that run perpendicular to the valley walls can often be moraines or

kame deltas from ice retreat and post-glacial lakes.

Kettles and undulatory surfaces indicate that sediment was

deposited on ice

Linear features running down valley parallel to the walls are eskers

deposited under ice.

Modern floodplains often have oxbow lakes, are very low relief, and

mark boundaries for fans.

New York State maps generated using Google Maps © 2010. All other images created using Global Mapper version 11.01 © 2010. Graphs

and chart created with Microsoft ® Office Excel ® 2007 © 2006. Poster created using Microsoft ® Office PowerPoint ® 2007 © 2006.

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