Marker horizons are a thin layer of feldspar. Marker horizon depths are measured each spring and fall. Each SET site has one marker horizon; three replicate cores are taken from each horizon during samplings. The depth of sediment accreted above the feldspar marker is measured on 4 side of the rectangular core using calipers. Measurements are made to the top of the feldspar layer. Cores are replaced after the measurements have been made. The values recorded in the data file represent sediment above marker horizon at the time of measurement. It is important to note that different cores are taken during each measurement, thus core A on date “X” can not be to compared to core A on date “Y”. For comparisons over time, measurements should be averaged over all “cores” and “replicates” for each individual SET. Cores or “Plugs” are taken from each horizon using a kitchen knife. This method is not ideal for several of our more wet sites. There is a high probability of erroneous measurement in sites that are very wet. We are working on a better method for sampling.

For more information on SET and Marker Horizons see: http://www.pwrc.usgs.gov/set

RESEARCH LOCATION:
Latitude and Longitude reported as decimal degrees in the NAD 83 Datum.
Elevation is reported as NAVD 88, orthometric height (meters), and is currently an unprocessed measurement of the SET insert pipe. For more information please contact Aaron Strong (astrong@mbl.edu). Locations for Levine’s SET 2-3 are not available at this time.

Site            SET #    Marker Horizon      LAT                LONG             Elevation       Marsh Type      Dominant Vegetation
                               Installation Date

Holy Island     1         04/30/03            42.73118814     -70.82625404      1.36             Low                 Spartina alterniflora (short)
Holy Island     2         04/30/03            42.7305772       -70.82672061      1.45           Transition          Spartina alterniflora (short)
Holy Island     3         04/30/03            42.73009768      -70.82693638     1.69            High                 Spartina patens
Laws Point     1         12/7/2000          42.73157969       -70.84149472     1.39            Low                  Spartina alterniflora (short)
Laws Point     2         12/7/2000          42.7312578         -70.84219796     1.40           Transition           Spartina alterniflora (short)
Laws Point     3         12/7/2000          42.73069447       -70.84275403     1.70            High                   Spartina patens
Levine’s          1         12/7/2000          42.72733649         -70.85228593   1.68            Low                   Spartina patens
Levine’s          2         12/7/2000                                                                              High                   Spartina alterniflora (short)
Levine’s          3          12/7/2000                                                                              High                   Spartina patens
Morris Island   1         05/01/03             42.72912254         -70.83472098   1.18            Low                    Spartina alterniflora (tall)
Morris Island    2         05/01/03            42.72923966          -70.83544812   1.07           Low                    Spartina alterniflora (tall)
Morris Island    3         05/01/03            42.72942128          -70.836324       1.13           Low                    Spartina alterniflora (tall)

Sampling your marker horizons http://www.pwrc.usgs.gov/set/readmarkers.html