Click on figures for larger images.

Figure 3.  Diagram showing results of a sediment-trap experiment in Bear Lake, Utah/Idaho, in which sediments were separated by layers of Teflon granules dispensed by an early version of the Intervalometer. Some intervals within the sediments of the collection tube were not clearly separated by the granules because of low sedimentation rates. The scale is in centimeters.

Figure 4.  Exterior view of Intervalometer. The disc shown is approximately 1 ¼ inches in diameter, and the instrument is approximately 3 9/16 inches in diameter by 12 inches in length.

Figure 5.  Photograph showing the lower section of the collection tube recovered from the Hueneme Canyon sediment trap, which was placed  30 m above the sea floor (30 mab). The edges of the discs deposited at 10-day intervals in the sediment column appear as horizontal white lines throughout the tube. Scale is in centimeters.

The originally designed Intervalometer included programmable instrumentation that deposited Teflon granules at timed intervals onto the surface of the sediment collected throughout the deployment period (Anderson, 1977). The resulting sediment profile was stratigraphically separated by a succession of unique Teflon layers that were deposited on a time-series basis (fig. 3). Under certain conditions, such as a low rate of sedimentation, high water content in the material in the collection tube or tilting of the trap from a vertical orientation, the granules tended to migrate or shift position within the sediments of the collection tube. This condition made interpretation and sampling difficult.

The Partition Intervalometer was subsequently redesigned by Roger Anderson to dispense hydrodynamically shaped Teflon discs (fig. 4). When released from the supply manifold, the disc vertically descends through the water in the trap and into the collection tube and settles upon the surface of sediment (fig. 5). This advance permits improved sampling procedures and interpretation of the sedimentary profile by more accurately defining unique sediment intervals throughout the sediment column.

Members of the USGS technical staff from the Woods Hole Science Center and Roger Anderson have entered into a joint agreement to provide, fabricate, and test prototype state-of-the-art instrumentation. Under this agreement, Anderson has provided the initial design specifications for the Partition Intervalometer, and the USGS has supplied materials, fabricated several units, furnished the necessary design modifications, and developed testing protocols for a prototype and several upgraded field versions of the instrumentation.