Sir,
We have read with interest the letter by Drs. H. J. Harrington and I. G. Speden in the March 1960 issue of this journal.Reference Harrington and Speden 1 However, after an examination of the photograph attached to that letter the writers would suggest a glacial chronology different from that of the original correspondents.
To us the most striking feature of this photograph is the presence of uniformly well developed patterned ground over the entire valley floor and parts of the valley sides. We feel that a relatively recent retreat such as that proposed by Drs. Harrington and Speden does not allow sufficient time for the development of patterned ground up to the very edge of the glacier. Rather, we believe that the most probable sequence of events is: (1) retreat, with four stillstands, a long time ago; (2) formation of patterned ground during the long interval when the ice edge was either at its present position or further back—the position of the ice edge in 1959 may well represent a r elatively recent advance over the patterned ground; and (3) present day stillstand or slight wastage of the front, permitting the formation of a new moraine ridge.
In support of this interpretation we refer to the recent work of Dr. Péwé. Working in this area Péwé found little or no advance or retreat of the fronts of many glaciers since the time of Griffith Taylor’s visit nearly 50 years ago. 2 Moreover, on the basis of a 14C date on algae in ablation moraine in front of the Hobbs Glacier, Péwé has stated that the minimum age for the last, or Koettlitz, ice cover is 6,000 years. Moraines presumed to be of this age which flank the Garwood Glacier are only 200 yards (180 m.) from the present edge of the ice.Reference Péwé 3
Furthermore, the occurrence of mummified seal carcasses in nearly every ice-free area around McMurdo Sound, and the C−14 dating of one of these carcasses (which lay on glacial drift in Taylor Dry Valley) at 1,600–2,600 years of age.Reference Péwé, Rivard and Llano 4 furnishes additional evidence that glacier recession has in general occurred quite some time ago.
30 May 1960
