Hancock-N Geo

 May 14^th, 04, the hiking group entered the Lake Hancock north area, by entering the private access of Dick Bowen, who lives just north of the lake.

 There is considerable slumping of the cliffs near his property. In places, the storms have caused 3 meter thick sections of the walls to spall off to the beach zone below. Otherwise, the storms have cleaned the space below the cliffs, so that one can walk directly to the cliffs, with no intervening logs, rubble, and vegetation. The stratigraphy is fresh, allowing sediments to be viewed with little weathering- this has happened during winter 03-04.

 Immediately below the first house to the north, there is indication of distortion of sediments, as evidenced by folding- this is just below the soil layers, and shows that the Esperance (iron stained sands) has been compressed since its deposition; this could have been done by the advance of the Vashon glacier in the last 20,000 years, but it more likely that the Ledgewood faulting has affected this zone (one mile south of the main fault). The hypothesis that the Vashon, proceeding almost due south, could have jammed local sediments, by compression, as it moved horizontally against the Greenbank scarp (which is seen in the cliff walls of the Hancock south area in the forma of lengthy thrust faults), will be tested for the surrounded area, by investigating the cliff walls.

 In the mile of cliffs analyzed, which are south of the Ledgewood main fault, there is considerable variation of the stratigraphy. At times the glacial till is 20-30 meters thick- all the way to the rim above. Other places have only wind blown sand and stream gravels, hence it appears that the underlying Possession till has been uplifted into the Esperance sands. In other places the cliff is almost entire blue clays (when damp), which test to be fresh water clays (devoid of salt taste). The whole zone south of the Ledgewood fault appears to be influenced by compressional forces. Since the faulting runs SE-ward towards Baby Island, inland it would still trace a path close to the cliffs. This will be tested by referring to the well water chemistry for neighboring wells.

 There were two separate fossil stream channels filled with gravels and sand, which had been overlain by level sands and gravels. These appear to have been oriented with the prevailing stress direction, which would have been NW-SE in mid glacial times (by faulting); the layering in the channels was not level, but tilted up to the south in both cases- this indicates that uplift has distorted their stratigraphy.

 The cliff geology did not confirm my hypothesis of tension of the north zone being caused by jamming of the N-S glacier movement against the scarp at Greenbank. There were some tensional faults (gravity dropping) but they were a mile north of the Lake. Immediately north of the Lake, there was massive till and finally glacial drift, and these showed hardly a shred of evidence of extension. It appears that the major features which we saw were the result of massive earthquakes and liquefaction during the middle glacial period. These were covered by later unconformable beds- which were almost level and which showed no sign of the underlying disruption. We did discover a spring just south of all the disruption and north of the massive tills, which was flowing fresh water (37 ohm-meters resistivity), and which was just below a sudden change of rock type (till changing to sand and silt sediments, indicating a normal fault). Sediments to the north appear to be upthrown- if I had found a spring to the north, it would have had to be more mineralized water (because of my thousands of cases, which show that the upthrown block has the more conductive water- both at the ground surface and in the subsurface as shown by electric logs).

 The till just below Dick Bowen's house is mid-glacial as indicated by stratigraphic position (below iron-stained sands- Esperance sand?), and by hardness test (stronger in compression than the Vashon tills). This till slopes down to the south by 5 degrees or so, which may be the result of differential rebound. Above the till, the iron stained sands are at an angle to the till (angular unconformity). The later Vashon could have slid down this slight slope towards the Greenbank scarp, causing the enormous thrust faults on the south side of the lake, and then later could have caused the iron-stained sands (by streams of melt water) as they retreated; if so the Vashon till was later removed by erosion, leaving only a few feet of drift.

 A map from water wells chemistry will be constructed, to show the orientation of faulting and fracturing, so that these unfinished analyses can be put on a better regional picture; there is too much local variation to understand these earth movements from two dimensions (cliff walls).