Introduction 1 Acknowledgments 2 Analytical Techniques 2 Dividing Reservoir Rock Samples into Available Hydrocarbon and Sediment Residue 2 Determining the Composition of the Available Hydrocarbon 2 Determining the Mineral Content of the Sediment Residue 2 Determining the Trace-Element Distribution 2 Bitumen and Heavy Oil Deposits 3 California 3 Kentucky 3 New Mexico 3 Oklahoma 4 Texas 4 Utah 4 Wyoming 4 Canada 5 Trinidad and Tobago 5 Venezuela 5 Discussion 5 References Cited 5 Appendix, Description of Sample Localities 17 TABlES [Tables follow References Cited] 1. Mineral content of the reservoir rock samples as determined semiquantitatively by X-ray diffraction 8 2. Composition of natural bitumen, heavy oil, and gilsonite 9 3-8. Trace-element content of reservoir rock, sediment residue, bitumen, heavy oil, and gilsonite samples from: 3. California 10 4. Kentucky and New Mexico 11 5. Oklahoma 12 6. Texas and Wyoming 13 7. Utah 14 8. Canada, Trinidad and Tobago, and Venezuela 15 9. Maximum and minimum trace-element contents of reservoir rock, sediment residue, and bitumen or heavy oil samples from all deposits 16 Contents Ill 0 API gravity.-The degree API gravity is the standard term devised by the American Petroleum Institute to specify the density of crude petroleum.