Thinking on Salt Marshes

It's a nice day with a little wind and lots of sun. I put in on a falling tide, cross the river, and head up into the Pope's/Long/Carting/Peacock Island complex.

I start by staying to the west heading around Peacock Island. There are a few Great Egrets, one late Osprey, and lots of Great Blue Herons. By the time I get to the top of Peacock Island, I have fifteen GBH sightings.

I can't make the passage between Carting and Peacock. The water is already quite shallow and there's a good chance of getting stuck halfway in. What water there is, is not wide enough to turn around in, and of course, the bottom in a salt marsh is nothing to walk on.

So, I take the channel between Long and Carting. Here, I notice that the cut banks of the island are well stratified. The top of the island is spartina alternaflora (cord grass - the long version of spartina). The layers are two to five inches thick and run down to the water level, which is about three feet at this time. Some of the layers are defined enough to form shelves several inches wide.  So, what causes this?

There are several possible sources for the layering, and not being an expert about this sort of thing, I am just guessing. But, I can toss out water level right away as this is a tidal zone with a twice daily fluctuation of about five feet - there is never a steady state water level. Also, two to five inch layers might represent something like ten to thirty years time spans (this is really a guess, but based on what I've estimated in the marsh 1-1/2 miles downstream.

    1. Ice - heavy winter ice or ice flow events scrapping or otherwise impacting the spartina surface
    2. Flooding
    3. Burning
    4. Agriculture - grazing or grass harvesting
    5. Drought or disease  

As to #3 and 4, there are two stone "trails" leading from the mainland to the islands, a distance of maybe 10 to 15 yards. A tide dam would be pointless given the geography, but these could be old fords so that someone could access the islands. Spartina was used for cattle feed in the old days through harvesting and direct grazing, if the ground was firm enough. The East River Marsh in Guilford has quite a bit of corduroy road exposed in the river bank, and that marsh was known to be used by farmers.