20 Fluvial Geomorphology of Post-Glacial Rivers

Sunday, 19 March 2017
3:45 PM - 5:45 PM
Allegheny, 17th Floor

DECOUPLING OF PUNCTUATED FLUVIAL LANDFORM DEVELOPMENT AND RIPARIAN VEGETATION SUCCESSION WITHIN THE LAKE ERIE GORGES PROVINCE OF WESTERN NEW YORK

Paper number: 20-3
Program: Theme Sessions
Time: 4:25 PM – 4:45 PM

Authors

Abstract

The recent fluvial geomorphology and riparian forest succession are investigated along bedrock-incised systems of the Lake Erie Gorges province, where middle-order streams occupy former meltwater channels of the late Pleistocene glacial margin. Rivers span the sedimentary spectrum from suspended- to bedload-dominated, the latter attributed to local reworking of till and colluvial inputs. The resulting complex mosaic of fluvioglacial landforms within the deeply entrenched river corridors is investigated from sedimentary, geophysical, and ecologic datasets to improve our understanding of interactions between post-glacial fluvial geomorphology and riparian vegetation-succession dynamics within flashy bedload-dominated fluvial systems of the northeastern United States.

While historic aerial photographs constrain landform chronologies and infer vegetative patterns as far back as 1929, established dendrochronologies and subsurface stratigraphic architectures resolved with GPR reveal older biogeomorphic patterns along aggradational terraces within Zoar Valley, the largest and least altered of the Lake Erie Gorges. In particular, juxtapositions of laterally-accreting bar-and-channel geometries are resolved beneath terraces that today show little surficial topographic manifestation of punctuated growth. The more recent photographic evidence documents the formation and evolution of younger channel-proximal fluvial landforms, providing a conceptual framework of how non-linear geomorphology drives riparian succession. The coupling of these two parameters over this readily observed timeframe attests to the primary importance of the geomorphic template in dictating long-term forest succession. Older terraces, while revealing subsurface architectures of similar punctuated growth and development, exhibit fewer topographic expressions of former channel and bar forms. The highest and most mature terraces within Zoar Valley host late-successional forest communities >200 years in age that no longer follow the geomorphic template seen in subsurface architectures. However, terraces of intermediate geomorphic position, while likewise devoid of suggestive surface topographies, continue to host forest communities that reflect the punctuated nature of landform evolution.

Geological Society of America Abstracts with Programs. Vol. 49, No. 2

doi: 10.1130/abs/2017NE-290148

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