Cantwell Formation Research Articles

Petroleum Source Potential and Thermal Maturity of Cantwell Formation (Paleocene), Central Alaska Range: A Reconnaissance Study: ABSTRACT

The Paleocene Cantwell Formation is a sequence of nonmarine sedimentary and volcanic rocks that is widely distributed in the central Alaska Range and locally is more than 3000 m thick. Mudstones and coals in the Cantwell were deposited in a variety of lacustrine and fluvial overbank environments and are of interest as potential source rocks of petroleum. Thirty-eight samples of mudstone and coal were collected from ten outcrops and analyzed using Rock-Eval pyrolysis, vitrinite reflectance (R/sub 0/), and thermal alteration index (TAI). The results suggest that these rocks may be potential sources of gas and possibly oil. Total organic carbon (TOC) in the samples is relatively high, averaging about 2.8% (range 0.5-14.2%) in the mudstones and about 28.8% (range 5.1-50.2%) in the coals. Plots of hydrogen and oxygen indices (HI and OI) on modified van Krevelen diagrams indicate kerogens of types III and IV. In addition, HI values are generally less than 150 and S2/S3 values are generally less than 3, indicating that these kerogens are gas prone. A few samples exhibit somewhat higher values of HI (up to 170) and S2/S3 (up to 18.6) and therefore may be capable of generating small amounts of oil. Values of T/sub max/more » (range 437-537/sup 0/C), median R/sub 0/ (range 0.63-4.28), and TAI (range 2.3.-3.8) show that the thermal maturity of the samples varies from mature to postmature with respect to the oil and gas windows.« less

Limits to northward drift of the Paleocene Cantwell Formation, central Alaska

Volcanic rocks of the Paleocene Cantwell Formation in central Alaska apparently originated at a paleolatitude of 83°N (α 95 = 9.7°), as indicated by paleomagnetic results. When compared with the Paleocene pole for the North American craton, the 95% confidence limits of the results suggest that terranes north of the Denali fault have moved no more than 550 km northward relative to the North American craton since Paleocene time.

The Cantwell Formation: A Continental Deposit of Tertiary age in the Alaska Range

Introductory statement.-The Cantwell formation comprises a of conglomerates and finer clastic sediments of important though restricted development within the Alaska Range. These rocks form a belt from 3 to 23 miles in width, which has its beginning near the northeast base of Mount McKinley and extends thence eastward for at least 1oo miles to Cathedral Mountain at the head of Susitna River. Its members attain their most typical and maximum expression adjacent to the Nenana Valley, intermediate between those two points. Historical.--In 1898, during a hasty exploratory trip into the Alaska Range, Elridge noted a series of conglomerates and coarse sandstones on the Nenana (then called Cantwell) River, between two tributaries later designated as Jack River and Yanert Fork, and referred briefly to this group of rocks as the Cantwell Conglomerate.2 Brooks and Prindle in 1902, on a geological reconnaissance of the Mount McKinley region, came across similar rocks at the foot of Muldrow Glacier3 near Mount McKinley, and following along their northern border traced their extension eastward into the Yanert Fork basin, mapping the area as the