Well, I’m new to blogging, but thought it might be interesting to post a running update of our field activity this year. This year’s project is to map the surface geology of the Shirley and Fairfield Bay quads in north central Arkansas. For those of you unfamiliar with the STATEMAP program, it is a cooperative grant program administered by the USGS to encourage the states to map their surface geology at the 1:24,000 scale. This is important because it is a basic inventory of materials at the earth’s surface in a given area. The topographic maps drawn at this scale are the typical 7.5-minute quadrangles which we use as a base map for the geologic data we generate from our field work. Each quad covers approximately 60 square miles, and we currently map two quads per year. To do this we spend 3 days a week in (or near) our field area from mid-July to mid-April each year. Basically, we try to find a town close by where there is lodging, restaurants and stores for basic supplies. This year we are working out of Greers Ferry.
By the way, let me introduce myself. I am Richard Hutto, and I have been mapping with the STATEMAP program since the 2005-6 field season. My field partner this year and for the past 4 years has been Danny Rains. This is our first week out this season, and it is hot and steamy as usual this early on. There has been plenty of rain this summer, and the rocks are covered by lush, dense growth.
This makes it hard to spot outcrops unless you’re right next to them. Danny and I could only make it out Tuesday and Wednesday this week, so only made it up two drainages. The reason we like to have a look at the drainages in an area is because that is one of the few places we are likely to see bedrock exposed at the surface. Another would be bluffs, but they are usually more difficult to get to and get around on. We need to see bedrock in order to determine what rock units (formations) underlie the erosional cover and hopefully discern contacts between them. We take points on these contacts, and when there are enough points, we can draw an inferred contact line on the base map and describe the formations between them. All this information goes on the geologic map of the quads we publish each year at the end of the season (June 30).
On Tuesday, we found an old Jeep trail down to the Middle Fork of the Little Red River almost 700 feet below Sally Flats which is in the northwest corner of the Shirley quad. We parked on the abandoned M&NA railroad grade and hiked up Arnold Hollow.
Found a good Cane Hill base and climbed on up to the Witts Springs; about 460 feet.
We followed a contour back to the Jeep trail and returned to the bottom.
The next day we came down the same road and walked up a small drainage south of Arnold Hollow. This one actually revealed a massive-, irregular-, channel-bedded Imo sandstone which has a calcareous, fossiliferous section above it.
On up was a thin-, ripple-bedded lower Cane Hill sandstone outcrop with a dry waterfall.
But higher still were some beautiful bluffs of basal Witts Springs sandstone.
After getting a couple points there, we had to bail off down the steep hillside and back to the Jeep for our return trip to Little Rock.
Snake count: 0
Tick attacks: light