1144 EXPLORATION GEOPHYSICS 



cipal limitations affecting field^ork in both mining and petroleum surveys 

 will be briefly considered. 



Petroleum Lands. — Broadly speaking, most potential petroleum lands in this coun- 

 try are owned in fee by farmers and stock men. Our agricultural and range lands often 

 occupy sedimentary basins underlain by great thicknesses of stratified rocks, where, of 

 course, most of our important oil and gas fields are found. It should be borne in mind 

 that the availability of these large tracts of privately-owned lands for geophysical pros- 

 pecting and the simplicity of acquiring sub-surface rights by means of a standard lease 

 have been two of the dominant factors contributing to the phenomenal growth of the 

 petroleum industry in the United States. In the majority of cases the reconnaissance 

 geophysical parties have free access to the ground before negotiations are opened by the 

 Land Department for leasing, simply by asking for permission to go upon the land. 

 Commonly it is not until the preliminary surveys are completed and some general 

 knowledge of the sub-surface structure is acquired that negotiations are opened with a 

 view to the formal leasing of certain selected tracts or acreage. 



The consideration for an oil and gas lease may vary from one to many dollars per 

 acre, depending on its location relative to producing wells and on the geological condi- 

 tions. In the case of wildcat acreage usually no bonus is paid, the only consideration 

 granted being the lessee's promise to drill a well within a given time period. It is 

 customary to hold large blocks of leases today simply by the payment of delay rentals. 



Lands of the public domain, that is, Federal lands within the limits of the various 

 states, may usually be investigated without permission from either the State or the 

 Federal government. Oil and gas leases on such lands are secured through the Depart- 

 ment of the Interior under the Public Land Leasing Act of 1920, as»amended. 



Mining Lands. — The mining laws and regulations of the civilized countries of the 

 world, governing the acquisition of mineral lands, can be broadly grouped under (a) the 

 concession system, and (b) the claim system. The concession systetn provides that 

 either the state or a private land owner may grant concessions or leases to individuals 

 or corporations. Under the so-called claim system, the individual, when conforming to 

 local regulations, has the right to locate or stake a claim in lands of public domain over 

 certain limited areas of ground. This latter system originated during the early develop- 

 ment of the Colorado and California mining districts. 



In the United States all metalliferous deposits, such as copper, gold, lead, zinc, 

 chromium, etc., found on lands of the public domain, may be acquired by locating 

 claims, following the claim system. As outlined above, petroleum and gas lands situated 

 in the public domain are acquired by leases under the concession system. No provision 

 is made in the United States for location of mining claims upon or within privately 

 owned lands. Only public mineral lands may be located and entered under the mining 

 laws. 



Our Federal and State mining laws are based on the Mining Act of 1872 (com- 

 monly known as the Apex Law), which holds that the right of property in mines is 

 dependent on physical discovery and development ; that is, actual discovery of mineral 

 in place is made the source of title, and subsequent development or working is the 

 condition of the continuance of that title. Specifically the law states : 



"No location of a mining claim shall He made until the discovery of the vein or 

 lode within the limits of the claim or location. Sufficient development work is required 

 to disclose signs of a vein, or if possible, its general course and indications that it con- 

 tains valuable minerals." These two principles constitute the basis of all our local 

 mining laws and regulations. Therefore discovery is the very pith of the present law. 

 Our forefathers made no allowance for the entry of the geophysicist on the scene. 



Moreover, the discoverer of the top of a mineral vein or lode, usually called the 

 apex, has the right to follow the vein or lode down the dip (with certain limitations) 

 even though this takes him onto adjacent properties under other ownership. This 

 feature of the law was framed to validate an ancient procedure long established in 



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