Part 6

Map, Notebook, and Pencil

It is most important to have some method of recording where the fossils were found. It is very easy to forget where the material was collected, and one should never rely on memory. A small pocket-sized notebook is inexpensive and just the right size to carry in the field.

A highway or county map should be used to find the geographic location of each collecting locality. Maps of Texas counties can be obtained from the Texas Highway Department, File D-10, Austin 14, Texas. These maps come in three different sizes, but for most purposes the 18×25-inch sheets, with a scale of ½ inch = 1 mile, will be satisfactory. These are available for all counties and may be purchased at a nominal price.

Magnifying Glass

A magnifying glass or hand lens (Pl. 5) is useful for looking at small specimens and will also prove helpful in examining the finer details of larger fossils. A 10-power magnification is satisfactory for most purposes, and several inexpensive models are available.

Paper or Cloth Bags

Small bags are useful in separating specimens from different localities. Heavy-duty hardware bags for large rough material and medium-weight grocery bags for smaller specimens may be used. Locality data may be written directly on the bag or on a label placed inside with the fossils. As an added precaution some collectors do both. The more serious collector may want to use a cloth geological sample bag (Pl. 5).

GEOLOGIC HAMMER (Chisel end) MAGNIFYING GLASS GEOLOGIC HAMMER (Pick end) COLLECTING BAG SAMPLE SACK

Other Useful Items

The items described above are those that are most needed and constitute the basic equipment of the fossil hunter. The serious amateur may wish to include certain additional items which will place his collecting on a more professional basis. Some of these accessory items are:

1. A topographic map of the collecting area. These are available for many parts of the State and are published and distributed at nominal cost by the United States Geological Survey, Washington, D. C., and/or Denver, Colorado. The Survey can supply an index sheet showing all such maps available for Texas.

2. A geologic map of the collecting area if one is available. The list of publications of the Bureau of Economic Geology should be consulted to see if a geologic report or map of the area has been published. This list may be obtained without charge from the Bureau of Economic Geology, The University of Texas, Austin 12, Texas.

3. The geologic map of Texas. Although a geologic map of Texas is included in this publication (Pl. 10), the scale is so small that its use is somewhat limited. For more detailed work a larger geologic map in color (scale: 1 inch = 31.56 miles) may be ordered from the Bureau. The sale price is 25 cents.

4. A compass for more accurate location of collecting localities.

5. Adhesive or masking tape. The locality information can be written on the tape and applied directly to the specimen.

6. Paper labels (about 3×5 inches). A properly completed label should be placed inside each bag of material.

WHERE TO LOOK

Knowing where to look for fossils is a very important part of fossil collecting. It has already been pointed out that igneous and metamorphic rocks are not likely to be fossiliferous, but that most fossils are found in marine sedimentary rocks. These sediments were deposited under conditions that were favorable for organisms during life and which facilitated preservation after death. Limestones, limy shales, and certain types of sandstones are typically deposited under such conditions.

One should look particularly for areas where rocks formed from marine sediments lie relatively flat and have not been greatly disturbed by heat, pressure, and other physical or chemical changes. If the rocks appear to have undergone considerable folding and fracturing, there is great likelihood that any fossils that were present have been destroyed or damaged by this action.

Quarries are good places to look but one should be sure to obtain permission before entering. Rock exposures in quarries are rather fresh but have undergone some weathering. Quarries have been opened in many of the limestone formations of Texas, and large numbers of fine specimens have been collected in some of these excavations. Certain Lower Cretaceous limestones are useful for road metal, building stone, or in the manufacture of portland cement, and extensive quarrying has been undertaken in the Edwards Plateau region of Texas (Pl. 9). Bones and petrified wood are frequently found in sand and gravel quarries in many parts of the State.

Particular attention should be given to all railroad and highway cuts as rocks exposed in this way are usually still in their original position and are fairly well weathered. Cuts made by recent construction are usually more productive after they have undergone a period of weathering as this helps to separate the fossils from their enclosing rocks.

Gullies, canyons, and stream beds are also good places to examine. These areas are continually subjected to the processes of erosion or stream action, and new material is uncovered year after year.

If there are abandoned coal mines nearby, the dumps of waste rock around the mine shafts could be checked. A careful examination of such waste may reveal fine specimens of well-preserved plant fossils.

Coal has been mined in several parts of Texas, and abandoned shafts or dumps are still present in some counties. The bituminous coals of Texas are predominantly Pennsylvanian in age, and mining has been carried on in the following counties: Eastland, Erath, Jack, Palo Pinto, Parker, Wise, Young.

HOW TO COLLECT

When a likely collecting spot has been located, the ground should be examined very carefully to see if there are any rock fragments which contain pieces of shell or the imprints of leaves or other organisms.

If the fossils have been freed by weathering, they can be easily picked up and placed in the bag. Many times, however, it will be necessary to take the hammer and very carefully remove the surrounding rock. Smaller specimens may be more safely freed with the careful use of the proper size chisel by gently tapping the chisel and gradually chipping away the matrix—the rock that is holding the specimen. After most of the matrix has been removed, the fossil should be carefully wrapped and placed in the collecting bag.

Before leaving a collecting locality, one should be sure to record its geographic location and the geologic age of the rock in which the fossils were found. The place should be located on the map and the locality entered in the notebook in such a manner that it could easily be located again for additional collecting. If a county or topographic map is available, it is wise to mark the locality on the map. The geographic and geologic data should be written on a label placed in the bag of fossils collected at that particular locality. In addition, many collectors find it helpful to write the locality on the outside of each bag of fossils.