BITUMEN-BEARING ROCKS 



101 



permit a detailed estimate of the total resources. 

 Many deposits are characterized by extreme and 

 abrupt vertical and lateral changes in bitumen con- 

 tent of the impregnated rock sequence. Evaluation 

 requires closely spaced surface and subsurface data 

 points, but in many areas it is not feasible to gather 

 such data. Thickness, percentage of bitumen, lateral 

 extent, and other characteristics of most of the 

 deposits are poorly known. The larger deposits for 

 which estimates have been made are given in table 

 19. Appraisal of other known deposits will result in 



Table 19. — Deposits of bitumen-bearing rocks in the United 

 States with resources of at least 1 million barrels 



.Sandstone 141-166 



Late Miocene Edna 



and early 

 Pliocene. 



Do South Casmalia Diatomaceous mudstone 



and vein deposits. 



Do North Casmalia do 



Pliocene Sisquoc 



Miocene Santa Cruz do 



Pliocene and McKittrick do 



Pleistocene. 

 Miocene Point Arena do 



ndstone 26-50 



Permian an< 

 Triassic 



Eocene 



Do 



Triassic 



Cretaceous a 

 Oligocene. 



Jurassic 



Eocene 



Tar Sand Triangle -Sandstone 10,000-18,100 



_P. R. Springs do 



-Sunnyside do 



.Circle Cliffs do 



Asphalt Ridge do 



.Whiterocks do 



-Hill Creek do 



-Lake Fork do 



-Raven Ridge do 



_Rim Rock do 



-3,700-4,000 

 -2,000-3,000 

 -1,000-1,300 

 -1,000-1,200 



--65-125 

 -300-400 

 .—16-20 

 -100-125 

 .—30-35 



Total 18,693-28,862 



an appreciable increase in the estimate of total re- 

 sources. Collation of information from exploratory 

 wells in the Rocky Mountain States that are known 

 to contain extensive subsurface tar-sand deposits 

 will add a major segment to the resource estimate. 



The major tar-sand deposits of the world (those 

 with more than 15 million barrels of bitumen in 



situ) are estimated to contain 915.2 billion barrels 

 of bitumen, of which about 710 billion barrels is 

 attributed to Canada and 200 billion barrels to 

 eastern Venezuela ( Phizackerley and Scott, 1967, 

 p. 551). Some other authors estimate that the east- 

 ern Venezuelan tar-sand resources are comparable 

 to those of Canada, and Burk (1971, p. 174) men- 

 tioned that although deposits in Colombia have not 

 been well defined, available information suggests 

 the possible presence of almost a trillion barrels of 

 bitumen in situ. Phizackerley and Scott (1967 p. 

 570) stated that very little information is available 

 concerning Russian tar sands, but that one Siberian 

 deposit reportedly contains impregnated Permian 

 sandstone in an area the same order of size as the 

 Athabaskan deposits. 



Numerous reports deal with bitumen-bearing 

 rocks in the United States, but few of these give 

 data that can be used for resource estimates. Ball 

 Associates, Ltd. (1965), in a survey of available 

 data, listed 546 occurrences of bitumen-bearing 

 rocks in 22 States, but scant data permit estimates 

 of partial resources for only seven States. Readers 

 who want details of individual deposits should con- 

 sult the report of Ball Associates, Ltd. (1965) and 

 a comprehensive annotated bibliography by Mullens 

 and Roberts (1972). Brief descriptions of some of 

 the more significant near-surface deposits, taken 

 mostly from the report of Ball Associates, Ltd. 

 (1965), follow. 



Alabama. — Bitumen is found in several beds of 

 sandstone and limestone of Mississippian age within 

 a northwest-trending band, about 70 miles long and 

 8 miles wide, that extends across six counties in the 

 northwestern part of Alabama. Some impregnated 

 beds are as much as 20 feet thick, although most are 

 less than 12 feet thick. Bitumen contents of as much 

 as 15 percent by weight have been reported for 

 assayed samples. The Alabama Geological Survey 

 is studying the deposits. 



Alaska. — Many bitumen-bearing rocks and oil 

 seeps in Alaska have been reported, but owing to 

 the nature of the terrain and structural deforma- 

 tion, little is known of the extent or thickness of 

 impregnated beds. 



California. — Nearly all bitumen deposits in Cali- 

 fornia occur near the margins of sedimentary basins 

 in rocks of Miocene and Pliocene age. The deposits 

 are concentrated in the southwestern part of the 

 State within 75 miles of the coast. Large tonnages 

 are available in San Luis Obispo, Santa Barbara, 

 Santa Cruz, and Kern Counties. In San Luis Obispo 

 and Santa Barbara Counties, large deposits have 

 been investigated for oil-mining possibilities, but 



