Ch. Fletcher et al., TIDAL WETLAND RECORD OF HOLOCENE SEA-LEVEL MOVEMENTS AND CLIMATE HISTORY, Palaeogeography, palaeoclimatology, palaeoecology, 102(3-4), 1993, pp. 177-213
Paleontological, geochemical, and lithological indicators of former ma
rine and nonmarine influence are correlated between 13 cores from a ti
dal wetland (Wolfe Glade) on the southeast coast of Delaware Bay. Twen
ty new radiocarbon dates are used to establish the chronostratigraphy
of marsh facies. Sediment iron content, weight loss on ignition, litho
logy, and remains of plants, diatoms and foraminifera (known to tolera
te specific tidal inundation cycles) are used to describe cored facies
originating from supratidal, intertidal and subtidal salt marsh suben
vironments. Pollen assemblages are used to infer local Holocene climat
e fluctuations and to reconstruct paleoenvironments during marsh evolu
tion. The record of paleoclimatology suggests the Atlantic Chron was w
arm with variable humidity in the region, whereas the Subboreal was do
minated by cool and humid conditions. The Subatlantic was warmer, and
initially dryer, with a cool humid phase prior to about 1 ka, returnin
g to warmer, humid conditions in the last several centuries. Local rel
ative sea-level movements are characterized by five rapid, short-term
episodes when the rate of sea-level rise accelerated relative to the r
ate of marsh aggradation. These episodes are recorded by transgressive
facies contacts at 5.3 +/- 0.2 ka, 4.4 +/- 0.2 ka, 4.0 +/- 0.2 ka, 3.
25 +/- 0.2 ka, and 1.8 +/- 0.2 ka, sidereal years. An earlier transgre
ssive facies contact dated 6.9 +/- 0.2 ka is probably not the product
of a true sea-level movement. Sea-level movements are recorded through
out the marsh as palustrine or high marsh peats or peaty muds overlain
by lower intertidal or subtidal marine deposits. Several features sug
gest that these episodes are local relative transgressions produced by
short-term accelerations in the rate of sea-level rise relative to ma
rsh aggradation: the contemporaneity and apparent suddenness of marine
inundations; the sequence of facies indicating marine drowning; the p
resence of similar events in marshes elsewhere in Delaware Bay; and th
e marsh-wide extent of indicative facies transitions. We propose that
the rapid and frequent sea-level movements observed in Wolfe Glade are
the result of surges and relaxations in the Gulf Stream (and associat
ed spin-up and partial collapse of the North Atlantic gyre) in respons
e to winds generated by changes in the North Atlantic atmospheric ther
mal gradient associated with Holocene climate fluctuations.