Soils Developed in Freshwater Marl Sediments in The Hagerstown (Great) Limestone Valley
Soils Developed in Freshwater Marl Sediments in The Hagerstown (Great) Limestone Valley
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Date
1993
Authors
Shaw, Joey N.
Advisor
Rabenhorst, Martin C.
Citation
Abstract
Certain calcareous soils occupying alluvial landscape positions in
the Hagerstown (Great) limestone valley of western Maryland have
developed from highly calcareous ( 60-100g/100g) marl sediments of
Holocene age which range in depth from .5m to over 8m. These marlderived
soils have a high pH ( 7. 5-8. 5) , low bulk density, and high
porosity (0.5 to 0.6). The carbonate in the marl was developed from
inorganic and biogenic processes. The marl was formed in now extinct
ponds which had inundated alluvial landscape positions during parts of
the Holocene period. Certain algae capable of accumulating carbonate
internally and externally developed the majority of the marl.
Pedogenic processes have transformed the marl sediments into highly
calcareous Mollisols. The presence of buried surface horizons and
coarse (> fine sand) carbonate forms render classification of these
soils problematic. The coarse carbonate forms were mainly biogenic
deposits, but these carbonates have been altered sufficiently by coating
with pedogenic carbonate to identify calcic horizons. The drainage
class is difficult to interpret as a result of the gleyed appearance of
the marl sediments (chroma <3) and the high pH of these soils which
inhibits Fe oxide reduction. Most of the marl-derived soils (70%) are
better drained than the previous classification indicates. These soils
have been mapped in the Great Valley in units named for the warners
series (fine-silty, carbonatic, mesic Fluvaquentic Haplaquolls) and the
Massenet ta series (fine-loamy, carbonatic, mesic, Fluvaquentic
Hapludolls). However, proper classification may place these soils in
the Typic Calciudolls subgroup. Some soils originally mapped in the very
poorly drained Dunning units are very poorly drained marl-derived soils.