One of the many fun things about blogging is that ideas, speculation, and research will often come in “over the transom” from readers. I was recently contacted by Mr. Carl Blanchard with what appears to be long simmering evidence of an Alaskan mega-tsunami at our favorite time period, the Pleistocene-Holocene transition. It would not garner a post but he makes references that indicate he knows the area pretty well, and has some geological knowledge. He has a certain kooky credibilty.
Carl’s prose is disturbingly direct, but filled with intriguing tid-bits of evidence. Blanchard reports that deposits of marine shells and other oceanic detritus found in the Juneau area stratigraphy were washed in from the sea by a wave, rather than having been laid down over time as glaciomarine deposits.
Apparently, the accepted explanation for the shells in the stratigraphy of the area is that once, not too long ago, under the sea, the layer was pressed down by glaciers, and that subsequently the landscape was lifted from the ocean bottom to many meters above present-day sea level when the glaciers receded after 12,900 bp.
Blanchard does not come out and say it, but he implies that this wave was so large that it was generated by a cosmic oceanic impact, not an earthquake.
I submit Blanchard’s telegramatic communication below for your review and commentary.
UPDATE II: Check out this modern abstract on the Gastineau Chanel formation: http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_131294.htm
Hi, this article is intended to describe some aspects of the findings related to the Pleistocene-Holocene boundary near Juneau, Alaska. Carl Blanchard.
Marine Shells @ the Pleistocene-Holocene Boundary @ Juneau, Alaska
The RC date for a large chaotic array of Marine shells near Auke Bay, Alaska is quite close to one frequently used date for the PH [sic Pleistocene – Holocene 12,900 BP] boundary. The mix of shells included unexpected forms, scallops and deep water barnacles are shells not observed on beaches in the area now however are still present in the inlet waters. Several species no longer in waters of the area are found in the Arctic Ocean now. These shells reflect much colder conditions for the area in general. *******
RC dates are little changed for the much warmer water species on Douglas Island near 10,000 years ago and all Arctic forms are absent. Hiatella Arctica represents the Pleistocene cold water and Saxidomus Giganteous indicates early Holocene conditions. *******
A large collection of shells from the site at 44 meters elevation was washed and sorted into 14 piles of similar forms. The most exotic were taken to the lab of the National Oceanic & Atmospheric Adm. @ Auke Bay for specific identification. Balanus Evermani typically found near 180 meter depth in the Juneau area inlets was the most intriguing. *******
Ocean currents of unusual nature near the PH boundary in the Atlantic Ocean near the Azores suggested a need for research. One immense flow had dismembered and transported coral, typical of shallow water, out to the Mid-Atlantic ridge. The depositional position of the coral indicated only one event @ 10,000 years ago had occurred. RC dates and the rapid replacement of the cold water forms seemed to indicate that the Juneau, Alaska area sites dating close to 10,000 years ago perhaps endured a similar surge from the Pacific Ocean. Surging of the Ocean toward the north could help explain the rapid warming of the area waters, especially as the Juneau area is far from the open ocean. *******
The arid nature of the Juneau area during the last cold period likely is a surprise. Pollen analysis of samples from Montana Creek strata indicated abundant sagebrush. This harmonizes with the even more surprising fact that large areas near Juneau have never once been glaciated [Auke Mt and central Lemon Creek]. A thin protruding dike about 4 meters high is close to massive talus blocks almost certainly indicating no glacial activity at that Lemon Creek site in several hundred thousand years. The high undisturbed stream gravel terrace along Lemon Creek provides additional evidence that a large portion of this stream valley has never been glaciated. One source claims a layer of excellently preserved marine shells is found within the terrace along Lemon Creek. Talus covered slopes surround the Auke Mountain area. Erratics are believed absent from most of the plateau while some streams have little total sediment. A predecessor or ancestral glacier larger than Mendenhall left a large pile of boulders as a terminus with no erratics beyond this point and thick talus slopes soon appear. The area seemingly has had no glaciers other than valley glaciers at any time in the past. Disjunct “Yellow Cedar” occupies this area as additional indication that this immediate area has not been disturbed by glaciation. This information limits the possible glacial effects on sea level from isostatic depression. *******
Marine shells encountered when the Treadwell ditch and flume was constructed are at the highest reported elevation of the Juneau area at 164 meters. Microfossils reported at 230 meters near the Montana Creek headwaters is the highest known evidence indicating former ocean level. Some rebound, hard to fully evaluate, has occurred in the Juneau area however the nature of the ice before the event sharply limits the maximum amount. Investigators of the USGS rejected the all encompassing and terrain covering ice sheet typically visualized for the late Pleistocene in the Juneau area. It was learned that many area glaciers were not even reaching the tidal area of the ocean. Aridity of the area revealed by pollen analysis supported this conclusion [the author was credited with the discovery of the layer containing organics permitting the pollen analysis] The strata analyzed for pollen also indicates that the ocean level was similar to the present level, or lower, in the Pleistocene before 39,000 years ago. McGinnis [tributary of Montana Creek] creek upstream from the organic layer has the 2nd highest elevation [130 meters] for reported occurrence of marine shells. Consensus likely exists among investigators that the Juneau high level marine phase was short lived rising from and returning to a much lower level in no more than a few thousand years. The highest deposits are poorly indicated apparently without a beach phase while unexpected forms [worm tubes, etc.] are present. The organic layer also has a level layer of volcanic ash [layers above the ash were sampled]. The marine shells at McGinnis Creek indicate that the associated diamicton achieved elevations that overlie the earlier land based deposits. The site of the marine shells is now about 10 meters higher than the pollen containing layer. Immediate dominance of Pine Pollen for a basal site investigated at the head of Montana Creek suggests that the Lodge Pole Pine remained throughout the Pleistocene on the Auke Mountain Plateau where this tree species still unexpectedly largely dominates the higher elevations. Peterson Lake, thought to be unrelated to glacial processes, is on the plateau therefore likely can confirm the continuous presence of pine trees by coring and pollen analysis. *******
Peterson Lake is shielded from all glacial events and at 250 meters in elevation apparently can test the surge thesis. The highest reported PH oceanic high stand level for the Juneau area was indicated by foraminifera @ 230 meters at the head of Montana Creek [Peterson Lake is 4km from this site] *******
A significant mystery involving marine shell deposition evolved 27 Km Northwest of Peterson Lake near the Lynn Canal seacoast. It was mentioned to the author during a flight over the area of Bridget Cove that a sand deposit was discovered during road construction as the work approached the watershed divide. Sand was not something expected in that bedrock dominated coastal area. Opportunity to inspect this site was delayed for a year or more when some of the anomalous sand was collected. When closely inspected at a later time the “sand” was entirely pulverized shells although not a single shell fragment was noted while briefly at the site [the deposit is about 3 meter thick & 60 meters above sea level] How could such a large deposit become so thoroughly pulverized [the rocky coastline suggests large eddies or vortices as one possibility]? *******
Indication of great pressure at a date and place where no ice was possible is another mystery although a suggestion of cementation is introduced by the highly alkaline water of this part of Douglas Island. The description indicating dense packing suggests high pressure of uncertain origin perhaps related to the depth of the water. Diamicton formation, as described by appropriate scientists, is regarded as a low pressure process dominated by drifting ice. Shell collections from northeastern Douglas Island are predominately of early Holocene age. *******
It is likely that no other place is as profoundly dominated by Pleistocene – Holocene transition events as the Juneau, Alaska area, perhaps the Puget Sound area is a close analogue. The rapid time frame is less apparent at Puget Sound and the evidence indicates an implausible confusing extreme short term oscillation of sea levels. The lower Fraser River was above sea level and ice free near 18,000 years ago however was destined to record the highest level for the subsequent marine invasion perhaps due to delayed rebound. Diamicton with articulated marine shells transgressed land areas while glacier ice was claimed absent near Bellingham, WA. Events of the Puget Sound area were also rapidly unfolding however are apparently slightly earlier than indicated at Juneau. The Puget Sound area had a dry climate before the onslaught of glacial events perhaps, in part, due to a lower sea level causing marine climatic effects to be more distant. The sea level claimed for Juneau is diametrically opposed by the general claim of far lower sea levels for that time period. Ice sheet loading is not a viable explanation for this discrepancy for the sea level at Juneau. Introduction of the diamicton sediments have not yet been demonstrated to result from the terminal glacial processes although the timing intuitionally suggests some relationship. Overridden land based RC dates should be earlier than the event however one of those at Bellingham, Wa. [10,370 years Bp] is well within the range at Juneau. 28 January 2008 Carl L. Blanchard slight revision & corrections have been made.