Soil examination of a potential LTER site in Beacon Valley
Description:
A bouldery surface, nearly all dolerite with some up to 2m but most >75cm; part of a gently northwards sloping, broad till plain valley floor; the surface is intermediate in age with younger till surfaces closer to the Taylor Glacier and older till surfaces at higher levels on the valley side; the ground surface is uneven with slight bouldery hummocks or rises separated by small flattish smoother patches; accumulations of pebble and granules in the lea of some boulders
Altitude:
1000 m
Aspect:
Nil
Slope:
0 °
Location Data
Observer
IBC
GPS
No
Latitude Longitude DMS
77° 49.95' S 160° 36.72' E
Latitude Longitude DD
-77.8325 160.61200
Latitude longitude precision DD
0.0004 0.00008
Locality
Beacon Valley upper Taylor Glacier McMurdo Dry Valley region, Transantarctic Mountains; about mid valley
Survey
Ross Island and Vicinity 1:250 000; US Geological Survey 1986
Climate
Soil climate zone:
Inland mountain
Estimated mean annual temperature:
-28
°C
Frozen ground depth:
0 N/Fnd
Frozen type:
Dry frozen
Frozen comment:
N/Fnd
Geology
Geological setting:
Beacon Valley is a very old valley with Miocene aged tills at higher levels in the valley; close to the glacier there is a series of well marked younger recessional moraines with granitic erratics indicative of earlier ice advances up valley from Taylor Glacier; granite erratics also occur in the old tills at higher elevations; the locally outcropping rocks are Beacon Sandstone and Ferrar Dolerite; these are present in the till which appears to be locally derived at this site as there is no sign of any erratics
Patterned ground:
Nil
Surface weathering or surface features:
Dolerite clasts strongly stained; some pitting on fine grained dolerite and moderate exfoliation on coarse grained dolerite; moderate to weak ventiforms; some polish on sheltered rock faces; moderate rounding from surface exfoliation; a few salt patches under some clasts
Soil
Soil parent material:
Sandy till from predominantly dolerite (70%) and sandstone, with dolerite boulders appearing to occur mainly on the surface and covering 20-30% of the surface
Xerous to subxerous; a dry site with no adjacent snow patches
Biological activity:
Nil observed
Profile Description
Horizon
Depth
Description
918a
-1
–
0
cm
surface cobbles; pebbles and granules forming a weakly pavementic surface; clasts subangular to rounded, some stained but some exfoliated; salts beneath some clasts; sharp boundary,
918b
0
–
2
cm
yellowish brown (10YR 5/4) pebbly granular sand; moderately cohesive; moderately developed vesicular structure; diffuse white salt flecks around stones; rock particles (dolerites) moderately stained but many internally altered to brown to strong brown (7.5YR 5/4 -5/6) oxidations; larger clasts mainly subrounded but smaller particles mainly rounded to subrounded; diffuse boundary,
918c
2
–
5
cm
yellowish brown (10YR 5/4) pebbly granular sandy; weakly cohesive; discontinuous salt patches; rock particles mainly subangular and stained and many altered; diffuse boundary,
918d
5
–
15
cm
very pale brown (10YR 5/4) granular pebbly sand with some cobbles; weakly to moderately cohesive; salts diffused through the horizon larger rock particles mainly angular sandstone and unstained; diffuse boundary,
918e
15
–
25
cm
yellowish brown (10YR 5/4) granular pebbly silty sand with occasional larger clasts; loose; rock particles mainly subangular, weakly to moderately stained and partly altered; diffuse boundary,
918f
25
–
40
cm
yellowish brown (10YR 5/4) granular pebbly silty sand with occasional larger clasts; loose; a few fine salt flecks; rock particles mainly subangular with smaller particles subrounded and partly altered; diffuse boundary, on yellowish brown gravelly sand