Page:1922 Bretz Notebook.pdf/1

SPOKANE QUADRANGLE|PANTOPS STA. ON INLAND EMPIRE ELECTRIC RR. AUG 1 19220 ON HILLTOP 1/4 MI EAST OF RR. GNEISSAC GRANITE, SCHISTOSITY DIPPING 35° TO SE, STRIKE N40-45°W. MAJOR JOINTS ARE NEARLY VERTICAL AND STRIKE N 10-12W PEGMATITE VEINS AND DIKES CUT THE GRANITE.

NORTH OF STATION ON WEST OF TRACK IS LARGE GRAVEL PIT EXCAVATED BY THE RR. GRAVEL IS FRESH, DARK GRAY IN CODOR, CURRENT-BEDDED WITH DIP TO SOUTHWARD. DEPTH EXPOSED IS ABOUT 30 FT. SCATTERED THRU THE STREAM GRAVEL ARE HUGE BLORS CHIEFLY OF GRANITE, AVERAGING 2-3 FEET DIAMETER. BLDRS SUBANGULAR. GRANITE OF LOCAL KIND, PEGMATITE IN SCHISTOSE.

THIS GRAVEL ACCUMULATION LOOKS FROM ITS TOPOGRAPHY AND ITS SITUATION WITH REFERENCE TO BOUNDING ROCK HILLS ON EAST AND WEST AND THE OPEN VALLEY TO THE SOUTH AS THO IT WERE DEPOSITED AS AN OUTWASH FAN AT THE EDGE OF THE ICE, THE ESCAPING WATER FLOWING SOUTHWARD. IT SLOPES OFF WITH A FAIRLY STEEP FRONT FOR AN ALLUVIAL FAN TO A NEARLY FLAT FLOOR JUST SOUTH OF PANTOPS STA. RANCHES ON THIS VALLEY FLOOR HAVE WELLS 120 FT TO WATER; DUG WELLS. THESE MUST BE IN THE SAME FLUVIOGLACIAL DEPOSIT BUT ON THE FLATTER SLOPES FARTHER FROM APEX OF THE FAN. BASALT HILLS TO THE WEST. LOOKS LIKE COLUMBIA LAVA IN EVERY RESPECT. HAS THE MOUNDS ON IT A PIT ABOUT A MILE N OF PANTOPS ON NORTHWARD SLOPE OF THE BASALT MESA HERE, SHOWS THE SAME THING AS AT PANTOPS. ALTITUDE IS ABOUT 25 FT HIGHER THAN THE PANTOPS DEPOSIT. MUCH BASALT IN THE COBBLES HERE, LITTLE AT PANTOPS. BOTH HAVE SOUTHWARD DIP OF CURRENT BEDS BUT IN THIS SECOND LOCALITY THE BEDS APPEAR TO DIP RIGHT AGAINST THE FLANK OF THE BASALT HILL.

ON THE BASALT MESA, THREE GRANITE BLDRS AT 50 FT ABOVE PANTOPS ALTITUDE. THE BIG ANBULAR OR SUBANGULAR BLORS IN THE PANTOPS PIT SHOW CONSIDERABLE DECOMPOSITION ON THE LESS-RUBBED SURFACE. THE GRAVEL IN WHICH THEY ARE EMBEDDED IS FRESH. IT IS OBVIOUSLY THAT THESE BLORS WERE DERIVED VERY LOCALLY; IN ALL PROBABILITY FORM THE GRANITE HILL ON WHICH THEY NOW LIECHT DERIVED FROM THE RESIDUAL BLDRS OF DECOMPOSITION, OUTLINES DETERMINED BY JOINTS AND SCHISTOSITY, NOT TORN OFF BY THE GLACIAL ICE.

WHY DO THEY OCCUR WAY UP IN THE STRATIFIED GRAVEL? THEY MIGHT WELL OCCUR IN THE BASE OF THE DEPOSIT, HOWEVER. IF ICE CAME OVER HILLS OF GRANITE CONSIDERABLY HIGHER THAN THIS PANTOPS DEPOSIT, THIS WOULD BE EASILY EXPLICABLE. MAY IT NOT BE CONCEIVABLE THAT ICE HAD NOTHING TO DO WITH THEIR DETATCHMENT AND TRANSPORTATION? MAY THEY NOT HAVE ROLLED AND SLID DOWN TO THE ACOUMULATING OUTWASH PLAIN? WHERE IN THE SPOKANE VICINITY ARE UNDOUBTED WISCONSIN TILL DEPOSITS? SPOKANE QUADRANGLE GARDEN SPRINGS-S.P. & S.RR AND O-W RR CUTS, 2-3 MILES SOUTHWEST OF SPOKANE

FOUR CUTS HERE ON EACH RR IN 2 MILES DISTANCE. CHIEFLY IN SHALE ALONG SP AND S; THO BASALT AND SANDSTONE ALSO EXPOSED. CHIEFLY IN BASALT ALONG O-W RR NPRR, ON EAST SIDE LATAH CREEK HERE, HAS ONLY GRAVEL EXPOSED. SHALE IS HARD AND BLOCKY WHEN DRY, DOES NOT WEATHER INTO LAMINAE VERY STRIKINGLY. CHIEFLY BUFF IN COLOR. SS GRAY, STRATIFIED, ALSO POORLY DEFINED. BOTH ROCKS ARE COMPOSED CHIEFLY 109T IRTS CAA GAA CHA AJUDMA 2¹ AGJE TISTO OR ENTIRELY OF VOLCANIC ASH.