Late glacial and Holocene history of the Penobscot River in the Penobscot Lowland, Maine

Bibliographic Data

ID12266240
AuthorsRoger LeB Hooke (School of Earth and Climate Sciences and Climate Change Institute, The University of Maine, USA, corresponding author), Paul R Hanson (0000-0002-8843-9987, University of Nebraska–Lincoln), Daniel F Belknap (School of Earth and Climate Sciences and Climate Change Institute, The University of Maine, USA), Alice R Kelley (0000-0002-8977-1033, School of Earth and Climate Sciences and Climate Change Institute, The University of Maine, USA)
Year2016
Volume27
Issue5
Pages726-739
Publication date2016-10-11
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueThe Holocene (JOURNAL)
Journal identifiersISSN: 0959-6836 • E-ISSN: 1477-0911
PublisherSAGE Publishing (PUBLISHER • US)
DOI10.1177/0959683616670474
OpenAlexW2531579401
LanguageEN
Citations received1
References cited49

When the Laurentide ice sheet retreated rapidly (~150 m/a) across the Penobscot Lowland between ~16 and ~15 ka, the area was isostatically depressed and became inundated by the sea. Silt and clay were deposited, but no significant moraines or deltas were formed. The Penobscot River was reborn at ~14 ka when ice retreated onto land in the upper reaches of the river’s East Branch. As isostatic rebound exceeded sea level rise from melting ice, the river extended itself southward. Between ~13.4 and 12.8 ka, it established a course across marine clay and underlying glacial till in the Lowland. Its gradient was low as differential rebound had not begun. Discharge, however, was higher and the river transported and deposited outwash gravel. During the cold, dry Younger Dryas, ~11 ka, eolian sand began to accumulate in dunes in the Lowland. Some of this sand, along with fluvial sediment from the headwaters, was redistributed into terraces along gentler stretches of the river and into a paleodelta in Penobscot Bay. Eolian activity continued to ~8 ka and aggradation in terraces until ~6 ka. The climate became wetter and warmer after ~6 ka, the dunes were stabilized by vegetation, the river began to downcut, and braiding became less intense. Pauses in the downcutting are reflected in discontinuous strath terraces. In due course, the river re-encountered the old outwash gravels, marine clay, glacial till, and, in a few places, bedrock. Its profile is now stepped, with gentle, gravel-bedded reaches between bedrock ribs that form rapids

Aggradation · Bedrock · Deglaciation · Fluvial · Geomorphology · Glacial period · Holocene · Ice sheet · Moraine · Outwash plain · River terraces · Silt · Tectonic uplift · Aeolian processes and effects · Geological formations and processes · Geology and Paleoclimatology Research · Geology · Oceanography