Holocene Sea Levels in Southeast Alaska: Preliminary Results

Abstract

ABSTRACT. Natural raised marine deposits and archaeological sites recently discovered in southeastern Alaska have been measured relative to mean sea level and radiocarbon dated. Plots of sites on Heceta and Prince of Wales islands are compared to those developed for British Columbia. The Heceta Island curve is comparable to that of the Queen Charlotte Islands, in which pre-Holocene shorelines were lower than present until about 10 O00 B.P. and then rose to a maximum of 15 m as1 by 8500 B.P., when gradual emergence began to bring the sea level down to its present position. In contrast, the Prince of Wales Islands data indicate that sea level remained a few metres above its present position beteen 10 O00 and 7000 B.P. -a time when the shores of mainland British Columbia were as much as 15 m below present sea level. Because Holocene sea levels are a function of isostatic rebound due to removal of glacial ice, as well as global sea level changes and tectonic activity, the implication is that whereas Heceta Island underwent processes and magnitudes of glaciation and isostatic rebound similar to the Queen Charlotte Islands, Prince of Wales Island was subjected to a pattern of glaciation and isostatic rebound different from that of the Queen Charlotte Islands and mainland of British Columbia.

Some Critical and Methodological Aspects of Shoreline Determination: Examples from the Baltic Sea Region

“…Andrews et al 1971;Cannon 2000;Clark and Fitzhugh 1992;McGhee 1979), as well as in Southeast Alaska (e.g. Giddings and Anderson 1986;Mobley 1988). Also, in the European North, along the coast of northern Norway resembling studies have found a solid ground (e.g.…”

Post-glacial sea-level change along the Pacific coast of North America

“…The shell date provides a minimum age for the ensuing transgression in the Gulf of Esquibel, which rose above the present datum around 10.7 to 10.1 ka BP. A high stand of less than þ16 m amsl at Heceta Island on the northern boundary of the Gulf of Esquibel was reached between 9.5 and 7.6 ka BP (Ackerman et al, 1985;Mobley, 1988;Baichtal and Carlson, 2010), while at Prince of Wales Island on the eastern boundary of the Gulf, RSL reached at least þ14 m amsl by 9.8 to 9.1 ka BP. Following the high stands, the sea regressed, reaching below þ14 m amsl on Heceta Island (Mobley, 1988) and approximately þ1 m amsl at Prince of Wales Island in the mid-Holocene (5.5 to 4.5 ka BP and 5.3 to 4.9 ka BP, respectively) (Fig.…”

A Predictive Model for Locating Early Holocene Archaeological Sites Based on Raised Shell‐Bearing Strata in Southeast Alaska, USA

“…Elevated terraces and shell‐bearing marine deposits have long been noted in Southeast Alaska (Buddington & Chapin, ; Swanston, , ; Ackerman, , ; Ackerman et al., ). Using these data as well as new information, Mobley () developed Holocene sea‐level curves for Heceta and Prince of Wales Islands based on the ages and elevations of raised shell‐bearing strata and compared them to those of British Columbia (Clague et al., ), as suggested by Rabich‐Campbell (). Clague et al () identified inner‐, middle‐, and outer‐coast paleoshorelines, with a forebulge influencing the middle and outer shoreline elevations.…”