<<UPDATE 3/31/24 - Looks like some of the trail is fenced off so if you can see the water from parking; make some observations and send them over as a temporary measure while we work with the Trail Association to confirm plans>>
Geological History
Approximately 21,000 years ago the glacial ice sheet that covered New England melted and left behind lakes and a mix of gravel, sand and clay in narrow valleys. When one of those lakes overflowed it cut a channel to Long Island Sound through one of these valleys, creating the Quinnipiac River watershed.
A report done by Yale University describes how the glacial movement formed this area (Flint 1965). “The drainage pattern as a whole is closely related to composition and structure of the bedrock. The predominating trend of streams is southerly, parallel with the structural trends of both the Triassic and the meta-morphic rocks. Streams avoid the igneous rocks completely. This general relation between stream positions and bedrock characteristics is much like that which would be expected had the region not been glaciated. The similarity leads to the inference that glaciation had little effect on the positions and forms of valleys and hills, which evidently were already present before the glacial invasion occurred.
Nevertheless, glaciation has influenced some stream valleys. The Quinnipiac, Mill, and West Rivers are now flowing, in places at least, on thick deposits of glacial drift, and hence may now the at positions different from those occupied before glaciation. In a few places, also, streams are interrupted by swamps or ponds, some of them occupying shallow basins created by the irregular deposition of glacial drift. The presence of such basins is one result of the recency of glaciation; since that event time has been too short to permit the re-establishment of uninterrupted stream flow”
Today the Quinnipiac starts in wetlands in Farmington and meanders south until it passes through North Haven, where is widens into a tidal marsh on its way to Long Island Sound.
Tidal Marsh Formation
A report from the Connecticut Experiment Station explains how tidal marshes are formed (Hill and Shearin 1970). “The deep, shallow and very shallow coastal marshes and the estuarine marshes of Connecticut and Rhode Island have been shaped by such geological events as glaciers, rising sea level and marine erosion by waves and longshore currents. To understand fully the properties of marsh sediments, we must first trace their history through the eyes of geologists.
Sudden geological events such as hurricanes and floods are recorded and well remembered by those who survive their wrath. But the slow balancing and adjusting of land and sea on the wrinkled skin of earth are scarcely perceptible in a lifetime. Geologists, however, digging into the margins of land and sea have traced the record of centuries of tides, erosion and changes in the level of the sea.
The last great glacier, which ground over New England 14,000 to 20,000 years ago halted its southernly push in the vicinity of Long Island. The heaps of soil and rock bulldozed along its front came to rest from Long Island northeastward along the Rhode Island coast….About 3,000 years ago the Connecticut coast stood about 9 feet below its present level. Thus, the sea rose on the Connecticut coastline only .3 feet per century. The slower rise of the sea permitted the open water in the protected bays and lagoons to fill with sediment carried by the tides. In the past 3,000 years sedimentation in Connecticut has kept pace with submergence…Today, submergence continues and the surface of the marsh slowly builds with remains of generations of plants and the silt and clay trapped by them at flood tide.”
Tidal Marsh Definition and Ecology
According to the Yale study, there are several types of classifications of swamps and marshes (Flint 1965)
Tidal marshes are wetlands that form where the land and ocean meet. They support all kinds of plant life as well as fishes and birds that feed on those plants and make their homes here. Tidal marshes help the environment by absorbing river pollutants and reducing the impact of flooding onshore.
Tidal marshes constitute a special category among the swamps within the New Haven area. They do not occupy basins hut lie at and upstream from the mouths of streams, and hence are open to the sea. They have resulted from submergence or "drowning" of the lower parts of valleys. The tides move in and out, creating an environment for the growth of specialized plants, mostly grasses. Within the area every valley or low-land that extends to the coast is floored wholly or partly with tidal marsh. Stream channels within the marshes normally have an intricate pattern of meanders. In some marshes, however, the natural channels have been replaced by straight artificial drainage ditches and are filling with vegetation. The vegetation of the marshes grades upstream, from grasses specialized to salt water into reeds, cattails, and bulrushes characteristic of water with low salinity.
The deposits of the tidal marshes consist of muddy peat and peaty mud, and form crudely wedge-shaped bodies that thicken seaward to a maximum of as much as 17 ft. Their seaward parts are underlain generally by gray, shell-hearing estuarine mud, their landward parts generally by alluvium. In the Quinnipiac Valley extreme high tides reach as far upstream as the northern edge of the New Haven quadrangle. The relations described indicate that the Connecticut coast has been undergoing gradual submergence by rise of sea level, subsidence of the land, or both.
Activities
Start at the parking to read some signs about the geology and ecology of the marsh. Then, proceed down the trail to a viewing point of the marsh at the second coordinates
1) Look around – do you see evidence of glacial movement and erosion; what do you see?
2) Based on the information above and your observations, why is this area considered a tidal marsh and not a swamp?
3) Is there evidence of erosion or changes in the tidal marsh – what do you observe and what do you think the impact will be over time?
References
Information above was referenced from the following sources:
- The north haven trail association (northaventrails.org)
- Flint, R (1965) The Surficial Geology of the New Haven and Woodmont Quadrangles Hartford, CT
- Hill, D. and Shearin A (1970) Tidal Marshes of Connecticut and Rhode Island New Haven, CT