Julia Daly

Date of Award

8-2002

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

Advisor

Daniel F. Belknap

Second Committee Member

Joseph T. Kelley

Third Committee Member

Kirk A. Maasch

Abstract

Analysis of basal salt-marsh peats and tide-gauge data from several locations around Newfoundland yield high-resolution late Holocene sea-level reconstructions and constrain differential sea-level change. The transition between rising and falling local sea levels and the influence of glacioisostasy on relative sea-level change around Newfoundland through the late Holocene are not well known fiom previous research. The patterns of local relative sea-level change during this time have important implications for constraining numerical models of sea-level change, and therefore inferences about ice sheet thickness and the response of the lithosphere to deglaciation. I investigated the stratigraphy of salt marshes at four locations around Newfoundland: a) Hynes Brook (SW), b) St. Paul's Inlet (west), c) Deadman's Bay (NE), and d) Placentia (SE). At each location, surficial samples were used to determine the modern floral and foraminifera1 zonation. These zones were applied to basal peat samples to constrain the paleo-mean high water (MHW) level associated with the sample. Sea-level histories for each location are constructed by combining AMS 14c dates with paleo-MHW ranges for a series of basal samples. At three locations (Hynes Brook, Deadman's Bay, Placentia), sea level has risen during this time. At St. Paul's Inlet, sea-level change during the late Holocene appears to have a more complex history. Sea level has remained close to present over the past 2,000 years, but may have experienced a subtle transition fiom falling to rising between 2000 and 1000 years BP. This trend contrasts strongly with the transgression interpreted at Hynes Brook, approximately 160 km to the southwest, and supports the hypothesis of continuing glacioisostatic influence on the Northern Peninsula. Identification of the timing and position of this hinge and differential late Holocene sealevel trends provide important constraints on numerical models predicting isostatic responses to deglaciation.

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