Geological Epochs In Other Anderson Time Travel Fiction I

In Poul Anderson's There Will Be Time (New York, 1973), Jack Havig's group of time travelers establishes its main base in the middle Pleistocene - maybe a million years ago? - close to where its adversary, the Eyrie, will be in the twenty second century.

Thus, Havig's base is much longer ago than the Time Patrol's Pleistocene Pyrenees lodge and also, of course, not only in a different timeline but also in a different kind of timeline with opposite rules of time travel:

circular causality but no causality violation, thus one single invariable timeline;
no instantaneous time hopping in temporal vehicles but instead lifespan-consuming time travel as a psychic power.

Time Patrol members can instantaneously jump into the Pleistocene or any earlier epoch whereas Havig's group must expend personal time and energy traveling by their own effort with aids like miniature oxygen tanks, a specially designed navigation device and caches en route and must also ferry everything that they want to use in the past one piece at a time. On the other hand, that far in the past, they are safely undetectable by their less well-organized enemies.

Their base, on a wooded hill near "...a mighty river..." (p. 157) sounds exactly like the Time Patrol Academy in the Oligocene.