Hyde Park Mastodon Research:
Pond Stratigraphy

Description of Units Observed at Lozier Pond, Hyde Park, New York

Unit 1
Coarse Detrital Peat

-Dark brown, 2.5Y 3/2
-Macro-organic material ubiquitous, with wood fragments (>10cm length) common.
- Top of this unit is missing from all stratigraphy in the pond due to several separate excavations of the site.

Unit 2
Humic carbonate-rich silty clay

-2.5Y 4/2
-Transition-zone between peat above and marl below
-Shelly material (gastropods, bivalves, ostracodes) grade from degraded and fragile at top of section to well preserved and relatively more abundant at base of section.
- Conversely, plant macrofossils are ubiquitous at top of section, decreasing but still common at base of section.
-Unit often appears mottled
- Contact with the unit above tends to be laterally variable, and is identified by a lighter color from that of Unit 1

Unit 3a
Uniform, Humic Silty Marl

-Generally olive gray 2.5Y 5/2
-Shells abundant
-Silt and sand components are significant
-Some mottling seen.
-Faint, visible laminations are rare, but do occur.
-Contact with the unit above tends to be laterally variable

Unit 3b
Banded and Laminated Marl

-Dark gray 5Y 4/1, with lighter gray laminations similar to the olive gray (2.5Y 5/2) of Unit 3a.
-Width of laminations fluctuates from 0.1 mm to >1 cm
-Shell frequency decreases at base of section.
-Inter-bedded poorly-sorted sands and gravels throughout, often appearing in discontinuous and sub-horizontal lenses. Lamination are generally sub-horizontal and wavy.
-Cobbles up to 15cm in diameter sometimes present, occasionally appearing to be suspended in matrix, but often contained within poorly-sorted sand and gravel layers.

Unit 4
Massive Clay

-Bluish-gray 5B 4/1
-Organic material and shells absent.
-Clay sediments generally well-sorted, with occasional thin (~1mm) laminations of poorly sorted, angular to subangular silt and sand. Otherwise, clay appears massive
-Occasional isolated subrounded cobbles up to 20cm in diameter occur, suspended in matrix.

Basal Gravel

-Subrounded and subangular, poorly sorted lithic fragments, up to 15cm in diameter.
-Thickness of unit is at least 30cm, and is interpreted to be glacially derived and present beneath the entire basin.
-Described in HPM-2 (pit trench).
-Encountered but not described in core LP2A and LP3A.

PLN 08/26/02

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