Digital Varves

Varves of the Month for 9/1/2010 - 9/30/2010

Varves from North Hatfield, Massachusetts

Scale bar in cm.

Click on image to download original image file

This month's varves are relatively thick gray varves from a 130-ft core taken in North Hatfield, Massachusetts west of the Connecticut River and just north of Northampton. The varves are from a depth of 108-110 ft. and the split core has been partially dried to make the summer and winter layers more easily discernable. The varves on this image have been matched to the North American Varve Chronology (NAVC) and numbers on the image (4887-4895) are NAVC (AM) varve years. A plot of the varve record from this site (NHT) matched to a record of Antevs (1922) and a core on the Univ. of Massachusetts campus in Amherst, Massachusetts (Rittenour, 1999), both translated to AM years, is also given below. The varves on the image were deposited at ~15,900 yr ago in an environment a few kilometers south of the receding ice front.

The NAVC in the Connecticut Valley shows abrupt changes in varve thickness that are maintained for at least a few decades. These positions in the varve chronology may represent times of lake level change or if varve thickness is not maintained for very long they may represent flood events into the Connecticut Valley from the release of water in tributary lakes.

The initial lake levels during ice recession in the Connecticut Valley of northern Connecticut were the first stages of glacial Lake Hitchcock. These lake levels developed into a high stable level draining to a spillway at New Britain, Connecticut. The lake was impounded in the Connecticut Valley behind a large mass of ice-contact stratified sediment at Rocky Hill, Connecticut that is designated as the dam for the lake. When this high stable level of Lake Hitchcock dropped to a lower level, also stable at a lower elevation, is not known and remains a point of controversy. At some point the lower stable version of Lake Hitchcock was established that drained through sediment that formed the dam for the initial high stable level at Rocky Hill. This lake level drop may have been a gradual event over a decade and might not be represented by a conspicuous change in varve thickness since water levels only fell about 10 meters. Deltas of the lower stable level occur throughout the Connecticut Valley of New Hampshire and Vermont and at the mouths of some tributaries in Massachusetts. In New Hampshire and Vermont this lake has been informally called the Cold River Stage after a large delta at the mouth of the Cold River in Walpole, NH.

Plot of the NAVC varve years 4820-4970 showing the change in varve thickness in the North Hatfield (NHT) record. Shown matched to the NHT record (green) are Antevs (1922) original "normal curve" for Massachusetts (blue, MAS37-52) and the UMass core (magenta, UMass46-61). The image of varves above shows varves 4887-4895 in the center of the plot. (~3MB)

The core from North Hatfield shows an abrupt change to thicker varves that may represent a change in lake level, perhaps the transition from the high stable level of Lake Hitchcock to the lower stable level (Cold River Stage), a transition that would have taken place when the receding ice front was between North Hatfield and Turners Falls, Massachusetts. An alternative hypothesis at North Hatfield is that the ice sheet readvanced to near this position and forced the increase in varve thickness as an ice-proximal environment was imposed on the core site. Varve thickness after the event is erratic with groups of thick varves (see plot) perhaps suggestive of approaching ice and a dynamic ice-proximal environment. A change in varve thickness is also seen in Antevs' normal curve (MAS37-53) and the Umass core (UMass46-61) but the thickness change is more subtle, although these other records do show the widespread nature of the event.


  • Antevs, Ernst, 1922, The recession of the last ice sheet in New England: American Geographical Society Research Series, no. 11, 120 p. (with a preface and contributions by J.W. Goldthwait).
  • Rittenour, T.M., 1999, Drainage history of glacial Lake Hitchcock, northeastern USA: Unpublished M.S. Thesis, Univ. of Massachusetts, Amherst, 179 p

Past Varves of the Month...