Page:The Journal of geology (IA journalofgeology21894univers).pdf/268

saddle, beyond which the crest of the divide is lower, and here the forest is seen to the best advantage. The most prominent object is an immense trunk, thirty inches in diameter and twenty feet long, lying where it fell at no very remote date, having broken from its roots at the surface of the ground, leaving portions of the stump still exposed. The entire root could probably be exhumed. About the present trunk the lines of splinters and smaller fragments clearly indicate the character of its branches and show that these branches remained attached at the time it fell. A considerable amount of silicified wood occurs also at the same locality as the cycads, obviously preserved by the same influences that preserved the latter. The slope from the fossil forest to the cycad bed is about the same as the dip of the strata. It is therefore probable that both occur approximately at the same horizon. The whole of this region, including the entire crest of the divide and extending to the bottom of the cañon below the cycad bed and far to the southeast, consists of the series of sandstones that have been treated in the Black Hills report as the "Dakota Group."

The great improbability that the cycads could have lived in the Dakota period, or Upper Cretaceous, led us to undertake an investigation of these rocks with a view to the possible discovery of additional evidence of their age. No other fossil remains than the wood and cycad trunks could be found in the immediate vicinity or anywhere on the outer slope of the Cretaceous rim. The crest above the fossil forest consists of harder sandstones, chiefly massive, which may be traced far around the Hills, and which form the upper part of the abrupt escarpment above the soft Jurassic and Red Beds. Passing over this to the northwest we descended into the first lateral cañon entering Red Valley from the northeast. The Jurassic is passed through and the Red Beds fairly entered in the descent. Fifty to seventy-five feet above the Jurassic contact and 175 to 200 feet below the summit of the crest, argillaceous shales with some carbonaceous matter occur interstratified with the sandstones, and at this level, partly in the shales and partly in the rocks, a few fos-