Palmer Hill Delta EarthCache
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Many of Maine’s blueberries fields and gravel pits are found on top of marine glacial deltas that were formed during the last ice age. This roadside pull off will give you to better understanding why these area are important.
The most recent glacial episode in Maine began about 25,000 years ago, when the Laurentide ice sheet overspread New England and Eastern Canada. During its peak development evidence of the direction of the glacier movement is preserved in the northwest-southeast striations and grooves visible in the bedrock in surrounding areas. Approximately 17,000 years ago, the ice reached its maximum extent, which extended beyond the current coastline onto the continental shelf. The slowly flowing ice was thick enough to cover Maine's highest mountains. It swept away much of the evidence of earlier glaciations, even removing the bedrock in many places. The weight of this glacier was so great that it depressed the underlying land mass. The ice began to retreat from the shelf between 17,000 and 15,000 years ago. As the ice withdrew, the land remained depressed due to the previous weight of the glacier, allowing marine waters to flood the coastal lowland. The land remained below sea level as it began to rebound until approximately 12,000 years ago when the present coastline was exposed above sea level.
Even as the ice margin withdrew, internal flow within the glacier continued to transport its sediment load southward toward the edge of the vast ice sheet. Large quantities of sediment were dumped into the ocean at the edge of the melting ice sheet, and these deposits are now exposed to view because the land rose above sea level. The coarser sediments and large boulders were dropped right at or near the edge of the glacier. The water-laid sediments were often deposited as layered accumulations. The clearest markers of glacial retreat are ridges of sediment called moraines. These ridges were heaped up along the edge of the glacier during brief periods (as short as a single year) when the ice margin remained in a stationary position or readvanced slightly. Scientists find moraines interesting because they good indicator of both the position and orientation of the glacial margin at a particular point in time.
But there is another feature that was formed at this glacial edge. Sand and gravel was also discharged in large quantities from glacial eskers, building submarine fans. Wherever the sediment supply was adequate and the glacier margin remained in one place long enough, these sediments built up to the ocean surface, eventually becoming flat-topped deposits known as glaciomarine deltas.
The posted coordinates will bring you to the edge of one of these glacial features. You are at the edge of the delta at the transition where the delta finally stopped growing and you will find yourself at an elevation of 260 feet above current sea level which was the sea level when this delta was formed. At the foot of the delta is the community of Tides Head, which is the up stream location of the tidal waters in the Sheepscot River. This delta has been extensively studied due to its location and the fact that the center is the Whitefield Pit give good information to researchers. If you look to the west and north at the posted coordinates carefully you will see the meltwater channels crossing the delta top.
Remember this is an earthcache so there is no container just an earth science lesson in an amazing natural area. To log this cache, you must post a photo of yourself with your GPS showing the delta in the background. At the posted coordinates you are on the Bailey Road where you can see in all directions very clearly. Email me through my profile a description of the difference between the northwestern and the southeastern views from this location. Try to think of an explanation of why there is such a difference. Please remember to include the name of the earthcache in your email.
Please remember these are cultivated blueberry fields so please stay on the roads and do not pick the blueberries. This and the other associated delta are perhaps most famous in Maine as "The Blueberry Barrens", since together they produce about 95% of the entire U. S. crop of low-bush blueberries each year. If you have never driven through a blueberry barren you will find it is a unique experience in all seasons. In the spring there are thousands of honeybees working to pollinating the blueberry plants. In the summer there is a unique kind of quite that falls over the barrens. In the fall the colors begin to show and the winter the snows form beautiful drifts that travel across the barren.
For more detailed information on the topic of marine deltas you might want to check for following web publications by the Maine Geological Survey
Maine's Glacial Moraines: Living on the Edge
(visit link)
Maine's Glacial Deltas
(visit link)
Surficial Geologic History of Maine
(visit link)
Generalized Surficial Geology of Maine
(visit link)
Lake Levels and Climate Change in Maine and Eastern North America
(visit link)
If you enjoy this earthcache you may want to check the Maine Geological Survey located at (visit link)
They have developed a number of information sheets or field localities giving a great deal of information about geologic features. They also have a number of books and maps about Maine’s natural history/ geology that you might find interesting.
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