John Day Fossil Beds Geology Road Log - Painted Hills to Sheep Rock Visitor Center

Painted Hills to Visitor Center
Geology Road Log

INSTRUCTIONS: The entire route covers about 75 miles, 30 miles more than the direct route. Please pull over at each stop rather than try to drive, read, and look (which is very dangerous). At each stop set your trip odometer to zero. Two-tenths of a mile from each stop start looking for the pull-off spot (odometers vary in accuracy). Pull-offs will be at least big enough for a medium sized RV, and graveled. If a pull-off is not available you will have to stop in the roadway (so marked) and then PLEASE, TURN ON YOUR FLASHERS TO WARN OTHERS. When you stop, keep your vehicle parallel to the road, in the direction you are traveling. The direction to look is given as clock time. The front of your car is pointing to 12 o'clock, directly right to 3 o'clock, etc. Have fun and please drive carefully!

ODOMETER distance between stops	PULL-OFF on left, right, or roadway	DESCRIPTION OF GEOLOGIC FEATURES
0.0	road way	THANK YOU FOR VISITING THE PAINTED HILLS! To start, drive from the restroom/picnic area location to the "T" intersection. Here set your odometer at zero. Make a right toward Route 26.
0.1	turn	(9 o'clock) The thick, reddish layer on the ridgeline is Picture Gorge Ignimbrite (28.7 mya), the same layer and event as the ignimbrite atop Cathedral Rock (later). Do not confuse it with the Picture Gorge Basalt Sub-Group (16 mya - part of the Columbia Plateau Flood Basalts) which make up the series of layers atop the Sutton Mountain ridgeline (2 o'clock).
0.2	road way	TURN RIGHT ONTO PAVED ROAD TO STATE ROUTE 26
1.4	road way	(3 & 4 o'clock) To the right, faults displace the neatly bedded and colorful lower John Day Formation layers. Fault-lines can be seen (look for a break and shift of layers).
1.4	right	(9 o'clock) A JOHN DAY BASALT ... On your left is an exposure of the olivine basalt at the base of red hillside of the Big Basin Member of the John Day Formation. These basalts are about 31.5 million years old and were extruded through cracks about five miles south of here. This lava is chemically different from the Clarno basalts, with which it can be confused. It's magma source was completely different. Its composition shows a major change in the collision geometry of the Pacific and North American tectonic plates. Outcrops such as this one offer data about events on a far greater scale than one might suppose.
1.2	road way	(9 o'clock) Exposures of Clarno basalts along the left side of the road and across Bridge Creek.
0.4	right	(3 o'clock) A MAMMOTH SITE ... In 1988 a mammoth tusk (about five feet long and now on display in the Bureau of Land Management Office in Prineville) was discovered and excavated from the contemporary gravels of an undercut streambank to the right. This medium-sized "elephant" was here when the landforms looked much as they do today, but with much cooler temperatures. The vegetation, however, was much different than today.
0.3	road way	(9 o'clock) In the roadcut on the left are (light colored) Clarno tuffs and ancient weathered lavas. Many of these lavas must have been subjected to long periods of humid and hot conditions to develop such prominent laterites. Black Butte is at 12 o'clock, dead ahead.
0.4	road way	(4 o'clock) To the west is a mottled hillside comprised of rhyolites and baked soils of the Clarno age (54-37 mya).
0.5	turn	TURN LEFT ONTO STATE ROUTE 26 TOWARD MITCHELL.
0.5	left	(all around the clock) Channel conglomerates of the Gable Creek Formation are throughout this roadcut. They are about the same age as the Goose rock Conglomerates, 100 MYA.
2.1	right	(9 o'clock) "Mitchell Rock," an intrusion of Clarno Formation andesite, on the other side of the highway. Mitchell Rock is the plug of a volcanic cone.
0.7	turn	Junction with Highway 207. TURN LEFT ONTO 207 TO SERVICE CREEK.
.25	left	(3 o'clock) Note the evenly, rhythmically-bedded Hudspeth mudstones. Calcium-rich siltstones are interbedded with silica-laden silts in this roadcut. What would cause such periodicity?
2.3	right & left	(6 and 7 o'clock) ANCIENT VOLCANOES ... On the hill directly behind (6 o'clock) is Bailey Butte, a prominent cap of the Clarno intrusive sill. There are also good views of White Butte (behind Bailey Butte) and Black Butte (7 o'clock), both Eocene volcanoes which surged through the conglomerates, shales, and other strata, severely deforming and, in places, metamorphosing those previously deposited rocks.
0.6	left	(10 o'clock) Meyer's Canyon. Permian metamorphics may be seen from here, with some difficulty. Permian fuselinids occur in the marble, and are the oldest fossils in this part of the state, about 240 million years in age!
1.9	left	(7 to 9 o'clock) The slopes have conglomerate-filled outcrops which are remnants of ancient coastlines.
2.8	right & left	(2 o'clock) More channel conglomerates of the Gable Creek Formation. How old are these? (about the same age as the Goose Rock Conglomerates)
0.6	right	(3 o'clock) "Hoo-doo" outcrops of Gable Creek conglomerates. These conglomerates may look similar in texture to some outcrops seen later along this route. (at Goose Rock)
1.2	road way	(9 o'clock) Junction with Gird's Creek Road to Twickenham. Stay on Rt. 207.
2.7	left	(9 o'clock) JUMBLED BEDS ... Notice the obvious, jumbled, steeply inclined Turtle Cove fossil bed layers (greenish). Angled Picture Gorge Ignimbrite (orange layer) top the beds. These "Blue Beds" (greenish) form the northwest flank of a deeply eroded anticline. Clarno Group basalts make up the low hills to the east (10 o'clock)
2.4	right	(4 o'clock) View of Keye's Mt. to the south. It is a forty-million year old Oligocene volcano composed of Upper Clarno Formation flows and breccias.
1.6	right	(9 o'clock) View of a structural downwarp known as Donelly Basin, with John Day Formation (greens) exposures noticable below the basalt layers of the ridgeline. The agricultural land is primarily situated where Cretaceous marine shales have surfaced.
1.9	road way	Road to the old townsite of Richmond. Continue driving on Rt. 207.
1.8	right	(5 o'clock) Across the canyon to the east was the Steele Energy well, drilled in 1984-85 to a depth of 6,400 feet into the Clarno Formation. The bottom of the well is in metamorphic greenschist and blueschist such as exposed back at Meyer's Canyon. Basalts exposed here near the drill site, in the center of the Donelly Dome (a hugh rise in this entire area), are Clarno Formation basalts.
0.9	right guard rail	(1 to 3 o'clock) Excellent viewpoint of slightly folded and faulted terrain toward the northeast and north as the road leaves the top of these basalts.
2.4	left after bridge	(5 o'clock) Look for the picturesque wall of basalts with mosses growing all over it. The wayside area you are about to pass on the right is a popular put-in spot for rafters and boaters of the John Day River. Area outfitters provide river recreation services.
0.4	turn	Confluence of Service Creek with John Day River. TURN RIGHT ONTO OREGON ROUTE 19. Around you are scenic exposures of the Twickenham Basalt Formation flow unit of the Picture Gorge Basalt subgroup. This particular flow is a porous, distinctive volcanic layer with small vesicles that contain crystals of exotic zeolites and other authigenic minerals.
11.6	right	JOHN DAY RIVER INTERPRETIVE WAYSIDE EXHIBIT pull-off area. You will soon pass through the town of Spray.
3.8	road way	Jct. with Oregon 207. Continue south along Route 19. Hardman and Heppner are to the north on Route 207.
0.8	right	(9 o'clock) HAYSTACK VALLEY MEMBER ... Along this section of road are exposures of the buff-colored Haystack Valley Member of the John Day Formation. Excellent fossils of camels and pronghorn, among the first known in North America, have been found in these rocks. Zeolites (note the pastel green layers) are represented in these claystone strata, although never attaining the thickness of the similar tuffs in the Turtle Cove member. In this valley you have left a syncline and entered an anticline which has exposed the older rocks under the basalt layers.
2.8	right	(all around the clock) SHADY GROVE RECREATION SITE - BLM ... The landscape around you might best be called the "Land of Basalts." These massive layers of flood (lava) basalts are part of the extensive Columbia Plateau Flood Basalts, which cover over 100,000 square miles of eastern Washington, Oregon, and northern Idaho. You are on the southern edge of this huge area. The Columbia Plateau Flood Basalts were formed primarily about 17 to 12 million years ago, some as recent as 6 mya. The thickest point of all these basalt layers is near Yakima, Washington, the total thickness about 15,000 feet. The basalt layers cooled from molten lava, generally into two forms, which you can see in the layers along the river. The six-sided, straight columns are primarily due to a very slow cooling rate. The braided, twisted, small columns are a result of swifter cooling, taking on the appearance of shattered glass. Both forms are possible in the same lava layer. If you head north you would eventually rise above these basalts to the fertile wheat fields of Oregon and Washington.
1.0	right & left	(5 o'clock) Here a small exposure of columnar (column-like) joints is surrounded by a confused-looking mass of "braided" basalt. How were these columns formed? (Hint: ponding of lava and slow cooling).
3.1	right	(7 o'clock) Here, a prominent basalt dike forms a vertical spine protruding out of the hill. Ahead, see if you can spot the linear dike in the hillside across the river. As you travel along the next few miles you will note road-cuts of almost pure white ash. This is Mazama Ash from the Mt. Mazama volcanic explosion about 7,700 years ago, which formed Oregon's Crater Lake.
0.7	right	(5 o'clock) On the other side of the river note the landslide block of Twickenham Basalt under an exposure of the (older, buff-colored) Kimberly Member, of the John Day Formation.
1.4	road way	Kimberly Store and Hamlet. Pass junction with road to Monument. Continue southward on Rt.19.
1.6	right	(5 o'clock) KIMBERLY DIKE ... The vertical wall of dark rock on the west side of the river is a basalt dike, named for the town of Kimberly. This dike is one of many remnants of lava which surged upward through massive cracks and covered incredibly large areas of the north- west about 16 million years ago. Later, the material in the crack cooled and slowly solidified, leaving dikes such as this one, while the material they passed through has long ago eroded away. Dozens of these dikes are around this region, part of the "Monument Dike Swarm" of the Picture Gorge Basalt Subgroup. Behind the dike is a small exposure of the Kimberly Member (see chart at end) of the John Day Formation. Note how the dike has cut through the older sediments of the John Day Formation.
1.3	right & left	(3 o'clock) Massive lava flows of the Dayville Basalt Formation of the Picture Gorge Basalt Subgroup (part of the extensive Columbia Plateau Flood Basalts) are on top of the buff-colored ash of the Kimberly Member of the John Day Formation. If you look carefully, you may see where the lowest lava flow thickened and thinned as it pooled or flowed over what were very shallow hills some 16 million years ago.
2.6	left	(8 o'clock) "ROUND UP FLAT"- Exposures of the upper Turtle Cove member 1/4 mile away.
2.0	right	At Mile Post 113...(10 o'clock) Note the river channel deposits on this road cut (rounded rocks in sediments, as opposed to edged rock debris in slope depositions).
0.6	right	(9 o'clock) 1/4 mile away is an exposure of the Turtle Cove member of the John Day Formation. The blue-green color banding is due to fossilized soil horizons, consisting primarily of claystone with a high density of both yellow and blue crystalled minerals.
0.6	turn left	Entrance to the "Foree" area of the National Monument. This round-trip 1.1 mile drive is very scenic, providing great views of the valley layers. Picnic tables, restrooms, water (except in winter), and very short self-guiding trails with exhibits are available. Outstanding fossils are collected from this area by scientists, with special authorization for scientific research. Visitors are reminded that all other collecting from monument lands is illegal.
2.0	right after the big curve	(6 o'clock) CATHEDRAL ROCK ... is a part of the John Day Formation. It is a section of earth which slumped from higher elevation and came to rest here. It forced the river to arc around it. The prominent red and buff bands on top are Picture Gorge Ignimbrite which was deposited as a fiery tidal wave of incandescent gas and volcanic debris from an enormous volcano explosion somewhere to the southwest nearer Newberry Crater. If the sun is right, you may see some of the ignimbrite shining, as it is a glass-like rock. The ignimbrite cooling duration remains problematical despite evidence of liesegang rings and other gelling peculiarities. The K/Ar date for this ignimbrite is 28.7 million years.
1.6	right & left	(7 o'clock) Note the eroded and unusually shaped rocks. Here Eocene (50 mya) hardpan soils that once buried the much older (200 mya) schists, marbles, and other metamorphosed rocks. The Eocene soils essentially buried the topography of the ancient landscape. These unusual outcrops, recently exposed by erosion, were surface features about 50 mya!
0.4	left	(9 o'clock) Dick Creek Road points to the distant "type area" for the Big Basin Member of the John Day Formation, noted for the red layers, like those of the Painted Hills.
0.5	left turn	BLUE BASIN ... Blue Basin contains the "type area" of the Turtle Cove member (see chart at end) of the John Day Formation. The very popular "Island-in-Time" trail affords an intimate view of one of the major erosional basins in this member (noted for its fantastic blue-green layers). Interpretive exhibits and fossil replicas are on display along this trail.
1.0	left & right	(10 o'clock) Deer Creek drainage. Formed as a result of the Middle Mountain fault, a 30 mile, east to west faultline with the south side risen upward. You are on the north side, the lowered side, just about to pass over the fault. It folded the Cretaceous deposits to the south into direct unconformable contact with the Miocene John Day Formation, now well below you here. The drainage you can see from here follows a portion of the fault line
0.6	left	(all around) GOOSE ROCK CONGLOMERATE ... These well-cemented (cliff) gravels are exposures of (Cretaceous) Goose Rock Conglomerate, named for nesting Canada geese. These rocks are about 110 million years old (my). Few fossils are found in the coarse pebbles and cobbles which are unsuited for preservation. Flow analysis suggests these deposits were an undersea channel-fan complex near a river mouth on a cosstline. Many of the gravels and clastic particles came from ancient mountains to the east and southeast.
1.5	left turn	From Oregon State Rt. 19 turn into the VISITOR CENTER parking lot. The visitor center has a fossil museum, bookstore, and films on the geologic history of the John Day Fossil Beds. The center is open daily from 9 to 5 pm, in winter closed weekends and holidays Thanksgiving through February, and in summer open until 6 pm Memorial day through Labor Day. No entrance fee.

Anticline:An upward "n" fold in strata.

Andesite: Volcanic Rock containing mostly plagioclase (composition NaAlSiO to CaAlSiO)

Authigenic: Generated on the spot. Term applied to growth in place of occurrence.

Breccia: Sedimentary Rock of sharp angular fragments.

Conglomerate: A sedimentary rock with pebbles cemented together by finer material.

Cretaceous: Time period from about 140 to 65 million years ago, end of the Age of Dinosaurs.

Dike: Tabular body of igneous rock that cuts across the layers of adjacent rock, or cuts massive rocks.

Formation: Formations possess certain distinctive or combination of distinctive lithic (rock fragments, not feldspar grains, are determining factor) features. Boundaries are not based on time criteria.

Fusilinids: A fossilized single-celled marine animal.

Group: A combination of formations (q.v.)

Ignimbrite: Rock unit which developed from a pyroclastic cloud of super-heated volcanic material (much like a fiery tidal wave) which, after settling, welded together by its own heat.

K\Ar: Radiometric, potassium-to-argon gas, decay isotope age determination.

Laterite: Soil profile leached of its aluminum, silica, and soluble materials but retaining oxides and hydroxides ofiron.

Liesegang: Rings or bands resulting from rhythmic precipitation in a gel.

Member: Subdivision of a formation (q.v.)

Metamorphic: Deformation in solid rock; by heat, pressure, or pronounced chemical action.

Rhyolitic: Volcanic rock containing mostly feldspar (composition Mal(AlSi)O were M can be K, Na, Ca, Ba, Rb, Sr, and Fe; makes up about 60% of the earth=s crust) and quartz (a mineral of SiO)

Syncline: A downward "u" shaped fold in the strata.

Type Area: Stratagraphic section recognized as the standard, generally the one from which a stratigraphic unit received its name.

Unconformity: Pertaining to an erosional contact where strata join discontinuously. Generally an obvious line between strata is visible, indicating the point of missing strata due to erosion.

Vesicle: Small cavity in a mineral or rock.

Zeolites: A group of hydrous aluminosilicate minerals, noted for their ease of ion exchange.

Mya = Million Years Ago