HR: 1340h
AN: PP43A-0593    [Abstracts]
TI: Deciphering the Depositional History of the Hudson Estuary and Estimating Summertime Precipitation Changes in the New York City area from the mid to late Holocene (7-1 ka)
AU: * Livelli, K
EM: livelli@gwu.edu
AF: The George Washington University, 2029 G St. NW, Washington, DC, 20052 United States
AU: Pekar, S F
EM: spekar@qc1.qc.edu
AF: Queens College, CUNY, 65-30 Kissena Blvd., Flushing, NY 11367 United States
AU: Pekar, S F
EM: spekar@qc1.qc.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, Route 9W, Palisades, NY 10964 United States
AU: McHugh, C
EM: cecilia@ldeo.columbia.edu
AF: Queens College, CUNY, 65-30 Kissena Blvd., Flushing, NY 11367 United States
AU: McHugh, C
EM: cecilia@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, Route 9W, Palisades, NY 10964 United States
AB: Paleosalinity estimates and sedimentation rates inferred from core samples from the Hudson Estuary indicate the influence of both the estuarine turbidity maximum (ETM) and climate changes in the evolution of the estuary from centennial to millennial timescales. Cores examined in this study are located in the segment of the Hudson Estuary 26 to 50 km upstream from Battery Park, the southern tip of Manhattan. An age model was constructed using C-14 dating. Paleoenvironmental interpretations are based upon paleosalinity estimates, grain size variability, and sedimentary structures. Summertime paleosalinity estimates were inferred from a new method using $\delta$$^{18}$O and $\delta$$^{13}$C records, as well as foraminiferal studies. Isotopic analyses were obtained from a narrow size fraction (1.0-1.7 mm) of bivalve shells of a single species ({\it Gemma gemma}). This represents the summer growth of a first-year bivalve shell, thereby reducing the uncertainty related to annual changes in temperature. Oxygen isotopes are dependent on temperature, whereas $\delta$$^{13}$C are not. The fact that both of the isotopic records correlate well indicates temperature played a minor role in the $\delta$$^{18}$O record. A good correlation in $\delta$$^{18}$O records exist among the cores of this study indicating that this new method for reconstructing a paleosalinity record is robust. Because salinity changes in the Hudson River are controlled by runoff/precipitation, these data can be used as a proxy for summertime precipitation changes in the Hudson River. These results suggest that the mid Holocene was characterized by major dry periods and greater variability in summertime precipitation during the mid Holocene (6-5 ka) with an abrupt increase in summertime precipitation occurring between 3 and 2 ka. Sedimentation rates in the Hudson estuary during the mid to late Holocene are generally low and are similar to the rate of sea-level rise in the Hudson River. Exceptions are high sedimentation rates observed in cores on the western side of the Hudson River in water depths of $>$4 m. These high sedimentation rates migrated during the Holocene and are related to a location of the ETM some 20 km upstream of its present position at 3.5 ka. The results of this study are consistent with the idea that at any time, estuarine sedimentation is highly localized, suggesting a more complex depositional pattern than previously indicated in estuarine stratigraphic models.
DE: 4870 Stable isotopes
DE: 4235 Estuarine processes
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting