Interpretive stratigraphy of the Lowville Limestone (medial Ordovician) of Central New York
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Abstract
Twelve stratigraphic sections of the medial Ordovician Louville
Limestone (Black River Group) were studied in the Utica and Little
Falls quadrangles of the central Mohawk River Valley in New York State.
In the study area the formation varies in thickness from about 30
to about 55 feet thick and includes two members separated by a dominant
intermediary unit which is not given a member status. The formation
consists of an interbedding of 9 lithologies, six of which are
volumetrically important. 153 large samples were cut, polished, and
studied in the laboratory.
The basal City Brook Member (new) varies in thickness from 4.4
to 15.6 feet thick and is characterized by thick beds of quartzose
calcarenite, capped in most sections by a metabentonite. The Tetradium-rich House Creek Member defined as the uppermost unit of the
Lowville Limestone in northwestern New York (Walker, 1973) is extended
into Central New York where it outcrops much less extensively, and
discontinuously, than its type area.
The stratigraphic sections can be lithically correlated by using
these distinguished members, a metabentonite, and a key marker horizon
zone. A time-stratigraphic cross-section of the formation suggests
that (1) the top of the formation is older eastward, (2) tne unconformity
with the overlying Trenton Group is larger eastward, (3) the
formation is time-stratigraphic in the area, and (4) the outcrop belt
in central New York is parallel to the paleoshoreline northwards along the southern margin of Adirondackia of Kay (1937).
Five lithofacies within the formation reflect five paleo-environments.
The lithofacies are inferred on the basis of lithology, textural
features, sedimentary structures and paleontologic considerations.
Eleven microscale features are recognized and given careful treatment
as to their identification, genesis and environmental significance.
They are: gas vents, hydrovents, vertical dessication, pelletoids,
planar birdseye, spherical birdseye, intraclasts, pseudolaminae,
vertical burrows, horizontal burrows and stylolites. Four macroscale
sedimentary structures are similarly considered: beach rock, tidal
channels, mudcracks and the status of layering.
The Lowville carbonates are close analogs of recent and ancient
nearshore, low gradient, low to high salinity, tidal carbonate environments.
The five recognized paleo-environments are, in their simplest
form: supratidal dolomite-forming, physically active mud flats; high
intertidal vertically borrowed, pelletal mud flats; low intertidal,
burrowed, poorly-laminated mud flats; shallow subtidal, burrowed, skeletal
muds; and a Tetradium-constructed wave baffle shoal facies.
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