Sunday, December 30, 2012

Lake Ontario dunes

Back in early September, I accompanied the sed/strat class at SU on a field trip to the eastern shores of Lake Ontario.
Field trip location marked on a map showing Lake Ontario and New York State.
The field trip was to look at part of a large freshwater barrier beach system that stretches for over 25km along the New York State shoreline of Lake Ontario.
Eastern Lake Ontario, with the approximate extent of the barrier/dune system outlined (the barriers are still visible on the map, immediately right of the dotted line.  The Tug Hill Region is shown for reference. Basemap created using

Our first stop was at Sandy Island Beach State Park, a tiny New York State Park between North and South Ponds. This section of the dune complex is over 1000 years old; most of the sand in the system has been inherited from previous highstands in the Ontario Basin (Woodrow et al., 2012). 
Two topographic maps of the Sandy Pond area: a National Geographic topo map on the left and a USGS topographic profile from on the right, both projected in Google Earth. Click for a larger version.

This beach is sandy, as the name implies, but it also has many well-rounded, hand-sized cobbles, especially just beyond the shore. These cobbles are not from the Appalachian Basin: some of the cobbles were granite, probably coming from the Canadian Shield.
Overlooking the beach at Sandy Island Beach State Park

Sandy Island Beach, looking northeast. 
Three types of sedimentary structures can be seen on the beach: ripples, dunes, and the arced shoreline. These are all bedforms, shaped by the movement of fluids (waves, wind, and currents): the ripples are small wavelength, the dunes are much larger wavelength, and the arc of the beach is the largest wavelength.
A trench dug in the beach (perpendicular to the shoreline) shows low-angle laminations dipping toward the water. Wave action has sorted the sand grains- the darker layers are darker, heavier minerals). 

Grass covered dunes landward of Sandy Island Beach
 From the beach, we met up with a boat that took us across North Pond to the barrier dunes.
Crossing North Pond (looking approximately southeast)
 At the other end of the pond is Sandy Pond Beach Unique Area, accessible only by boat. A boardwalk has been built to cross from the pond-side to the lake-side. This protects the dune from humans and humans from poison ivy.
Dunes with trees! The highest dunes in the area (NOT pictured) are 15m above Lake Ontario.

The beach on the pond-side of the barrier island had some very cool dendritic traces. They were composed of raised networks of sand and were quite extensive. I don't know if they formed on top of the beach like they're pictured, or if a layer of sand covering them washed away. If anyone knows what creature created these, please let me know in the comments!
Mystery trace/burrow. 

The lake-side of the barrier dune complex.

Beach on a barrier island. We were invited to join some beach-goers for an afternoon party, but reluctantly declined. 

I can't remember if this sand profile is perpendicular to the shoreline or not. If it is, the laminations look very different than on the first beach we visited.

The sand has built up inside the channel so much that plants are growing there. Needless to say, it is problematic for boaters trying to get into Lake Ontario.

Birds in the shallow water just inside the channel entrance.

Our boat, waiting while we check out the channel.

This great board explains sand transport to beachgoers. 

*Woodrow et al, 2012 can be found here: