Clay Soils of the Champlain

Valley

Clay Symposium – Middlebury College - June 2012

What to expect…

• Soils 101: particle size, soil structure, clay characteristics

• Formation of Clay/Silt Lacustrine Deposits

• Champlain Valley Clays (as mapped by NRCS)

• Improving Soil Maps - using modern technology

• Use & management of clays – potential pitfalls

Clay soils in the Champlain Valley make up some of the

best farmland in Vermont

There are some very significant

agronomic / engineering challenges

with clay soil

• compaction if worked when wet – causing

damage to the structure of the soil

• drainage problems –

Small particles impede water movement

The surface can become sealed when compacted

• In dry summers, it can turn into concrete-like

material

• cracking can cause damage to foundations, etc.

How do you know when you are looking at clay soil?

Particle size –

causes different

lengths of time for

suspension in

water

Sand sinks

Clay stays

suspended

To rate as a “clay” in the USDA textural system there

needs to be > 40% of clay sized particles

Clays often have platly structure

at the micro scale… And the macro scale

kaolinite

Platy structure

Compaction will further eliminate pore space in

clay dominated soils

Significance of Soil Structure:

Soil structure determines the amount

and arrangement of empty spaces in

the soil, influencing on how readily

water moves through the soil and

where plant roots can grow.

Soil structure = the grouping of individual soil particles into

clusters or aggregates, called peds.

The development of structure is an indication of soil formation.

Soil structure

effects water

movement in

soils

In our region

clays often have

platy or massive

structure

Understanding Soil Maps

& Formation of Clay / Silt

Lacustrine Deposits in VT

In the deeper, quieter water

successive layers of clay (and silt)

were deposited

The landscape as a whole…

Monkton - Addison County, Vermont

Till on hills – above

glacial lake level

An old

beach –

Stetson

series

Old Lake bed -

lacustrine soils

Soil maps have an

attribute “Parent

Material” allows

the Lacustrine (in

green) influenced

soils to jump out

from the Till (in

pink & magenta)

In 3-D -- Drape of Parent Material over topography –

where lucustrine deposits meet glacial till (in Johnson,

Vermont)

Legend for Soil

Parent Material

Parent material = The unconsolidated & more or less chemically

weathered mineral or organic matter from which the solum (upper part

of soil horizons A, E, B) of soils is developed by pedogenic processes

Proglacial Lake, Iceland

Imagine a very different landscape from the present –

glaciers melting – glacial lakes forming

Size & depth of these lakes changed constantly

Huge amounts of sediment washed into glacial

lakes from the largely denuded landscape

the result : thick lake-laid sediments of varying

particle size -- both silt and clay

Varves-

“silt- clay

couplets”

Annual depositional

cycle

Silty summer layers (more inflow)

Clay-rich winter layers – surface ice

encourages settling of clay size

particles by reducing wind shear &

surface mixing

Photo by G. Springston

G. Springston

Close-up of

varved silty

clay and silt

One

Year

Finer

materials

Clays – may take

many months to

settle a thin layer

Silts – may

get many

inches of

sediment in

short time

period

Note year to year

variation in

thickness

What was lake bed

& sea floor is now

dry land

Champlain Sea

– we need a digital

version of this map –

produced by GIS & on-

the ground evidence

(research need)

For a period of

time salt water

intruded into what

is now Lake

Champlain

This map is based on GIS

modeling & not all geologists

are happy with this particular

configuration of land / water

As the iced melted the surface of the

earth slowly rebounded…

in between melting & rebound of

the crust – sea water from the

Atlantic flooded the St.

Lawrence & the Champlain

lowlands

Proof of the

salt water

intrusion

Whales in

Vermont?

Vermont Surficial Geologic Map from 1970

Middlebury is definitely under water

From Ridge, J.C.,

2003, unpublished

handout

The ice damming the water

at the north end, at what is

now Warwick, Quebec,

failed catastrophically about

10,000 years ago. The lake

dropped 300 feet (91 m) in a

matter of days.

Eventually, when the glacier

retreated far enough north,

salt water swept in,

replacing the larger,

freshwater Lake Vermont

with the smaller,

saltwater Champlain Sea

Different layers of sediment –

side view

Lake

Many different glacial advances

& retreats over geologic time

Within various major glaciations - many mini advances, retreats &

re-advances

Many lake levels – different

elevations for shorelines & ancient

lake beds >>> highly variable soils

• Clay on top of till

• Till on top of clay

• Alluvial deposits on top of clay

• Etc. etc. etc. – lots of variations

• Current day drainage incising through ancient clay plains

• Not a neat / clear cut pattern

Champlain Valley Clays

(lake-laid sediment)

A close-up look at some

soil profiles & typical

landscapes

Glacial Till & Alluvium

can be deposited on top

of clay deposits – Lewis

Creek

Chunks of varved clay

gouged out of streambed

during storm events are

washed downstream

No this is not rock – but varved clay in streambed –

at 600 ft elevation

Lewis Creek

Addison

County, VT

Varved clay exposure – 400 ft elevation –

old lake floor being incised by current day Lewis Creek

Addison County, VT

Franklin County –

sometimes the clay

layers are below 6 feet

Soil Survey only looks

so far in terms of

depth – 6 feet Is where the Soil

Survey ends

In the Champlain Valley

you find lots of

Vergennes clay –

those areas that were

under various lake

stages and the

Champlain Sea

Flat to rolling terrain in

Monkton – Addison

Co.

Heavy clay soils catena in Addison County, Vermont

Landscape position often dictates depth to water table but not

always! Especially in clays – can get lateral movement of water

Catena key

Differences in Soil Drainage –

define different soil series

within the same type of clay

deposit

Covington / Panton

pd

Livingston

vpd

Vergennes

mwd

A catena of

clay soils:

Vergennes Clay

• moderately well drained soils on glacial

lake plains

• the series is extensive - about 250,000

acres in VT & New York

• a benchmark series and is in the

“soil series Hall of Fame”

Vergennes

Clay Soil

Profile

A

Bt1

Bt2

C1

C2

Hit varved

clay at 36

inches!

Calcium Nodules – found throughout the pit

Varved Clay

Pedon ID: Pedon ID: S07VT007004 - Charlotte, Vermont

Sampled in 2007 P study along Lewis Creek

Horizon Field Texture Lab Texture

A C C

Bt1 C C

Bt2 C C

C1 C C

C2 C Cl

Surface texture – low sand , medium silt

– high percentage of clay sized particles

% clay is very high in Vergennes Clay soils

58VT001006 - Addison Co.,

Vermont

Wow!!!!!!!!!!!!!

Pedon ID: S02VT-007-002 - Chittenden Co., Vermont

Impressive amounts of clay

Mapping in the Champlain Valley

dates from the ‘40,‘50s &’60s

• Using GIS tools vast improvements could

be made to the consistency of the

mapping

• It is all now in digital format but no editing

was done to the content of the maps –

except glaring errors

Vergennes Clay is in green – alluvial deposits

along Lewis Creek Corridor in other colors

See

anything

suspicious?

Lidar Imagery for

the NEK – Soil

Mapping may soon

be done using

remote sensing

Compare 30 m DEM to

Lidar elevation data

Increases the ability to pick out

land forms

New Technology

We need Lidar to improve the mapping in the Champlain Valley – VT Geologic al

Survey is using Lidar -- NRCS should be using this fantastic resource too

Use & management clay is not for amateurs

BEWARE

Incising smaller streams on clay soils are adding to the sediment load going in Lake Champlain

A serious

erosion

problem in

clays

There is a raging debate as to the erosion rates of clays &

aggregate stability of clays for VT (& NY) clays

• Need for more studies with the clays found in our region

• To “harmonize” the data T values (acceptable soil loss for Conservation

Planning) need to match other regions

• Instead of planning for 2 T it could change to 5 T – net result more

continuous corn planted, more P going in the Lake

“little research has been completed

on the erosivity of clay soils…”

The bottom line…

• We need definitive science based on

research (not estimates from nomo-graphs)

before changing K factors and Tolerable

Soil Loss Values -- which will have a huge

impact on water quality of Lake Champlain

• Hopefully we will be conducting studies on

this topic under the MLRA structure &

University research would be a plus

Issues when trying to farm

lacustrine influenced soils

Sedimentation,

runoff, streambank

erosion

Plowing in a wet spring can

be a challenge!

Very fertile soils - but slow

to warm

Engineering concerns – with

lacustrine influenced soils

Not always a great place to build a house

Photo Jim Kim –

VT Geological

Survey

Prone to

landslides

Clay layers can impede water movement – the clay

itself or coarser material on top can become saturated

– then mass failures can occur

All is not well in Vergennes

From GeoDesigns Inc

Concerns – with lacustrine influened soils

Not always ideal for septic systems

Questions / Comments…

Soil Characterization Data – Lincoln, NB National NRCS Lab:

http://ncsslabdatamart.sc.egov.usda.gov/default.htm

Email: Caroline.Alves@vt.usda.gov

Phone???? 865-7895 x203 – office has been closed to air quality problems - only

check phone once a day