Clay Soils of the Champlain Valley

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 Platy structure kaolinite 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 Old Lake bed - lacustrine soils An old beach – Stetson series 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 Finer materials Silts – may One get many Clays – may take inches of Year many months to sediment in settle a thin layer short time period Close-up of varved silty clay and silt Note year to year variation in thickness G. Springston 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 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 This map is based on GIS modeling & not all geologists are happy with this particular configuration of land / water Whales in Vermont? Proof of the salt water intrusion Vermont Surficial Geologic Map from 1970 Middlebury is definitely under water 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 From Ridge, J.C., 2003, unpublished handout 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 Catena key Landscape position often dictates depth to water table but not always! Especially in clays – can get lateral movement of water A catena of clay soils: Livingston Covington / Panton Vergennes vpd pd mwd Differences in Soil Drainage – define different soil series within the same type of clay deposit 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 A Profile Bt1 Hit varved clay at 36 Bt2 inches! C1 C2 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? New Technology 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 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 Plowing in a wet spring can be a challenge! Very fertile soils - but slow to warm Sedimentation, runoff, streambank erosion Engineering concerns – with lacustrine influenced soils Prone to landslides Photo Jim Kim – VT Geological Not always a great place to build a house Survey 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: [email protected] Phone???? 865-7895 x203 – office has been closed to air quality problems - only check phone once a day .

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