At least four times during the late Pliocene and early Pleistocene pyroclastic eruptions in the Jemez volcanic field, northern Rio Grande rift, flooded the ancestral Rio Grande with gravel-size pumice. Following as much as 400 km of fluvial transport, the pumice was deposited in beds 0.2 to 2.0 m thick in the Camp Rice Formation of the southern Rio Grande rift. A combination of reversal magnetostratigraphy and single-crystal sanidine 40Ar/39Ar dating constrains the ages of pumice-clast conglomerates at 3.1, ~ 2.0, 1.6, and 1.6 Ma. The coarsest pumice beds (cobbles, boulders) were deposited as antidune-like bedforms in a fluvial channel and as a crevasse-play sheet. Granule and pebble-sized pumice was deposited as dune bedforms in a fluvial channels and as ripple bedforms on the floodplain. The abundance of pumice clasts in the gravel fraction (60-100%) suggest very rapid transport downriver, probably in a few days or weeks. The two older pumice-clast conglomerates correlate with the Puye Formation in the Jemez volcanic field, whereas the younger two are coeval to the Lower Bandelier Tuff and Cerro Toledo Rhyolite.