NOTES 



FOSSIL TREE STUMPS FOUND IN SITU 



ON SUBMERGED RIDGE AT 



AMCHITKA ISLAND, ALASKA' 



Two ancient tree stumps, in situ and partially 

 embedded in bedrock, were found at a depth of 

 23 m off the Bering Sea coast of Amchitka 

 Island in the western Aleutians. The stumps 

 were found by the authors in October 1972 

 approximately 1.1 km north-northwest of Banjo 

 Point (Figure 1) during underwater surveys of 

 physical and biological damage associated with 

 recent nuclear testing on Amchitka. 



The two stumps were located at the base of a 

 narrow ridge of bedrock which is over 100 m in 

 length, rises abruptly from a generally level 

 bedrock bottom at a depth of about 23 m, and is 

 oriented approximately normal to the adjacent 

 coastline. The height and thickness of the ridge 

 range from about 4 to 8 m, and its clifflike faces 

 are nearly vertical. This ridge is thought to be 

 an abandoned erosional sea stack related to a 

 brief stillstand of sea level during Pleistocene 

 time at about 20 to 30 m below present sea level 

 (L. M. Gard, U.S. Geological Survey, Denver, 

 CO 80225, pers. comm.). 



Each of the stumps is about 1 m high and 

 seems to have a trunk diameter of about 30 to 

 40 cm. The one stump that was studied in detail 

 is located in a slight recess at the base of the 

 west face of the ridge (Figure 2). The base of 

 the stump is at the level of the generally hori- 

 zontal bedrock sea floor which extends westward 

 from the ridge; at this place the ridge face is 8 

 m high. The stump itself is mostly surrounded 

 by undisturbed bedrock (Figures 3, 4). With the 

 exception of lower root extremities which 

 extend outward several centimeters from the 

 base of the cliff and disappear into the adjacent 

 horizontal substrate, the stump is flush with or 

 slightly recessed into the cliff face. 



Directly above the stump in the roof of the 

 rock recess is a vertical cylindrical hole about 

 20 cm in diameter and depth. The existence of a 

 small diameter opening extending upward 

 through the rock was indicated by a stream of 

 fine air bubbles escaping from the cliff face 

 about 4 m above the stump. The air was from 

 the divers' exhalations that had become trapped 

 in the hole above the stump. It appears that the 

 stump had originally been totally encased in 

 bedrock but was then partly exposed as the cliff 

 face eroded away. The hole above the stump 

 may once have contained a higher portion of the 

 tree trunk, but the wood within the hole disin- 

 tegrated, leaving the cavity in the rock. 



Additional wood material was found in the 

 immediate vicinity of the stump. On the horizon- 

 tal bedrock sea floor within 2 to 5 m from the 



500 



500 



=1 



METERS 



N 

 I 



SUBMERGED RIDGE 

 WITH TREE STUMPS 



BANJO POINT 



KEY MAP 



' This work was supported by the U.S. Atomic Energy 

 Commission as a part of its Amchitka Bioenvironmental 

 Program. 



Figure 1. — Location of submerged ridge with in situ tree 

 slumps in relation to the adjacent shoreline of Amchitka 

 Island, Alaska. 



1099 



