Crystal Spring Recreation Area, with a good Corps Ramp
- Lake Ouachita is one of the clearest water lakes in the country. It is nestled in the folds of the Ouachita Mountains, and has many arms, coves and reaches to explore. It is one of the finest mid-continent lakes for cruising. We would recommend spring and fall, when it is less crowded.
------A Geo-Float Trail? Wow, that's enough to get a geologist's heart 'athumpin'. The Corps of Engineers has put together a booklet and set navigation marks for a self-guiding geology field trip on the lake, and it is a good one. The Corps even supplies an interpreter for groups of 15 or more, so local school groups rent a pontoon boat and have a day on the lake while learning about their local geology. When you visit the lake, get a free brochure and do some geo-floating.
A Stop on the Geo-Float 'Trail'
------ This is a big lake, with almost 50,000 acres. The real treasure, though, are the '1000 Islands.' Big, and small - forested and barren - with coves, beaches, anchorages, and perfect campsites everywhere.
------ Lake Ouachita ('Wash-It-Ah') is a perfect lake to spend a week or two holiday with the family. It is also a lake surrounded by wild land. The Corps owns most of the shoreline and there is a bare minimum of development. I am writing this on an anchorage and, except for the moon, there is not a light to be seen. For those who enjoy fishing, we have sometimes had difficulty finding the bottom with our sounder because of all the fish that get in the way.
------ Lake Ouachita formed when Blakely Mountain Dam blocked the Ouachita River in the mid-fifties. The waters of the lake invaded those long linear valleys, giving the lake a form that looks like a giant crab, with arms and legs extending everywhere out from the main body. It is a fascinating lake that virtually demands exploration - "What do you think is up that arm?" Anchorages abound, but those long skinny arms are often full of stumps and trees, left for fish habitat by the Corps. We lift one engine and one of us stands on the bow watching through the clear water ahead for hazards when we come into an anchorage.
A Stumpy Anchorage
ROCKS, OF COURSE
------The Ouachita Mountains are composed of long, linear east-west ridges of sandstone, chert and limestone. These sediments were deposited off the southern edge of the North American continent throughout most of Paleozoic time. To read about the regional setting of the Ouachitas, head over to our thread on Ark Rocks. These rocks are some of the finest examples of deep ocean sediments to be seen in the US , and geologists from all over the world come here to study the rocks.
------The abyssal plain has unique deposits. Generally, only the finest and least soluble sediments survive the long descent through the depths, far from land. Fossils are rare, since most organic or shell material is dissolved, eaten, or decayed before reaching the bottom. There are powerful currents in the depths, however, usually the result of landslides of debris off the continental shelf, triggered by earthquakes and powered by the weight of the dense cloud of suspended fine debris. These turbidity currents roar down the shelf and out onto the abyssal plain, snapping trans-oceanic cables and depositing a characteristic sequence of sediment. Each flow is nearly identical to others so a cyclic pattern is evident in the sequence of sediments that ultimately harden to rock. These deposits are called flysch or turbidites.
---- -Sometimes the turbidity currents suspended large gravels and boulders as landslide debris and carried the cobbles out to the abyssal plain.
------Toward the end of the Paleozoic, South America moved against North America, closing the intervening sea and thrusting the 30,000 feet of accumulated sea floor sediment up onto the margin of our continent. The uplifted Ouachita Mountains are a melange of low-angle faults, intensely folded sediment, and interlayered sub-oceanic volcanic ash deposits.
------The last phases of movement intensely fractured the mountains, sometimes into a dramatic checkboard pattern.
------Deep crustal fluid, saturated with silica, invaded the fractures depositing quartz. These quartz veins are often filled with beautiful crystals. Our launch site, Crystal Springs, is named for the nearby abundance of quartz crystals.
------In this climate, soft shales and siltstones form valleys, since they erode faster than well-cemented sandstones and limestones. Geologists call the topography 'inverted,' since ordinarily limestone, being slightly soluble, forms lowlands not ridges. The resulting topography is linear, flat-topped mountains with stepped flanks of outcropping limestone.
A ROCK WALK
A BIOLOGY WALK
(11 - 04)
Top | Home