Ice and Iron

Ice and Iron is a 1974 science fiction novel by Wilson Tucker, featuring large amounts of prehistoric content. The novel places a large emphasis on glacier geology.

Plot
The novel follows two separate narrative streams, one in the near future, where the onset of a new ice age has caused Canada to become buried under an advancing glacier, and another seemingly in the past, where the retreat of a glacier results in conflict between primitive humans and an invading army. In the "near future" timeline, the mysterious appearance of random organic matter, bricks, and human corpses near the glacier is investigated by a scientific team, and Fisher Yann Highsmith theorizes that corpses are appearing from the future, due to their brown haired and blue eyed phenotype not matching the ancient Native Americans that would have lived near the glacier in ancient times. The "past" timeline is revealed to be occurring thousands of years in the future, as the matriarchal descendants of Americans who fled south from the glacier advance northward conquering new territory from the now primitive inhabitants of the northern regions. The detritus near the glacier is the result of time travel guns being used near the glacier. After the appearance of two living humans near the glacier, Highsmith is able to definitively confirm his theory before the base is shut down due to the advance of the glacier.

Near Future

 * Fisher Yann Highsmith, a scientific "reconstructionist", who attempts to determine what the source and cause of the detritus near the glacier is. After some iteration, his time travel theory is confirmed.
 * Harley, a male medical doctor in Highsmith's team.
 * Jeanmarie, a female "polylibrarian", capable of recalling any fact she has read. Her knowledge is instrumental in the development of Highsmith's theory.
 * The corporal a man on watch duty who converses with Highsmith.
 * The pilot, a surly man who sleeps a great deal.
 * Seventeen, a living man who falls from the sky onto the glacier. The time travel gun that came with him is instrumental in developing Highsmith's theory.
 * Eighteen, a living woman who falls near the investigatory base. Her garments and the altered version of Spanish she speaks provide the final definitive proof of Highmsith's theory.

Far Future

 * The brickmaker, a primitive man who steals a time travel gun from an invading force, and is later sent back in time with it, and is designated "Seventeen".
 * The boatman, a primitive man whose canoe travels back in time.
 * The trackers, two men who free some slaves of the invading force.
 * The slave, a former farmer, enslaved at a young age, part of the invading force, who flees after two soldiers who befriended him are killed by the trackers.
 * The stalking man, who kills two soldiers, but is hit with a time travel gun
 * The scribe, a man living in the matriarchal kingdom to the far south of the glacier, sent by his young queen to investigate and record the invasion of the north. He is killed when the boat he is traveling on is ambushed by a group of "barbarians".