Significant thicknesses of carbonaceous shales at HAFO occur for about 25 m stratigraphically above the middle member.
Finally, the climate estimates will be paired with the revised chronology for HAFO (Ruez, in review).
Global circulation models (GCMs) have estimated repeatedly the mean annual temperature for the HAFO area in the Pliocene at about 3.
Although GCMs do not provide the resolution necessary to examine the faunal shifts at HAFO in light of environmental changes, they can be used to suggest which areas changed in concert with southern Idaho in the Pliocene.
2 Ma, which encompasses the Glenns Ferry Formation deposits at HAFO, each dataset was rescaled so that the total temperature variation was the same for all.
The lower half of the interval at HAFO is marked by slight cooling (Fig.
Because sediment deposition rates at HAFO vary between levels of known age (e.
The Pliocene interval represented by the Glenns Ferry Formation at HAFO is generally characterized as a wetter and warmer time period than today.
However, the concordance of the temperature trends of the global pattern and the Arizona data suggest the same trend may be applicable to the Pliocene deposits at HAFO.
Pliocene precipitation at HAFO is more difficult to assess, but a single interval of abundant surface water is here recognized.