Table 1. Characteristics of five major types of paleosols represented in the Chilga strata.

Paleosol Type and Stratigraphic Occurrrence	Horizon¹	Thickness (m)*	Nodule and rhizolith composition	Mineralogy²	Interpreted Drainage Class	Interpreted Surface Runoff
A: Protosol Throughout Chilga Beds	A	0-0.12	Lignitic roots and silicified rhizoliths	M, K, I	Moderately Well to Very Poorly Drained	Very Slow to Slow
	AC, BCss	0.13-0.95	Lignitic roots and silicified rhizoliths	M, K, I
	C	0.07->1.50	-	M, K, I
B: Histosol Throughout Chilga Beds	Oa, Oe, Oi	0.10 to 0.70	Lignitic roots	-	Very Poorly Drained	Ponded
	Ag, Aj	0.05-0.21	Lignitic roots	-
	Bcg	0.09-0.53	Lignitic Roots and mm-scale spherulitc siderite	K, M, S, I
	Cg	0->1.50	-	-
C: Gleysol Throughout Chilga Beds	Oa, Oe	0-0.10	Lignitic roots		Very Poorly to poorly drained	Ponded to very slow runoff
	A	0-0.12	Lignitic roots	K, M
	Bcg1	0.14-0.47	mm-scale spherulitic siderite and hematite	K, S, M
	Bcg2, Bcnss	0-0.72	mm-scale spherulitic siderite and hematite	-
	Cg	0- >1.50	-
D: Vertisol Throughout Chilga Beds	AB	0-0.23			Poorly to somewhat poorly drained	Seasonally ponded to very slow runoff
	Bss	0.21-1.37
	Bgss1	0.23-0.47		M, K
	Bgnss	0.35-0.59	mm-scale spherulitic siderite and hematite	M, K, S
	C	0->1.50
E: Argillisol Upper 40 m of Chilga Beds	A	0-0.08			Moderately well to somewhat poorly drained	Very Slow runoff
	ABt	0.10-0.14
	Bt, Btss	0.25-0.37		M, K
	BC, Bss	0-0.47
	C	0->1.50

*The range of thicknesses, in meters, of the various pedogenic horizons represented within paleosols. Note that not all horizons shown may be present in every paleosol (i.e., why some horizons have a range that includes 0 m).
¹Horizon names and properties follow the USDA Soil Survey Staff (1975; 1998) guidelines. Soil horizon names: O horizon – surface layer dominated by in situ accumulation of organic material, primarily vegetable matter; A horizon – “topsoil” layer, zone of organic matter accumulation and mineral removal (eluvial layer); B horizon – “subsoil” layer(s), zone of soil structural development and mineral accumulation (illuvial layer) that is derived from overlying eluvial layers; AB horizon – a near surface horizon exhibiting intermediate properties between an A and B horizon; C horizon – subsoil layer(s) composed of barely weathered material; C-horizons occur beneath A or B horizons. Subordinate indicators of soil properties: a – highly decomposed organic matter, very few to no recognizable plant parts; used only with O horizons; c – presence of concretions or hard nodules; e – partly decomposed organic matter, <1/2 of mass composed of recognizable plant parts; used only with O horizons; g – evidence for strong gleying, or highly reducing and wet soil conditions. Generally Indicated by chromas < 2.; i – slightly decomposed organic matter, >1/2 of mass composed of recognizable plant parts used only with O horizons; j – accumulation of jarosite; ss – presence of slickensides. Numerical descriptors (e.g., Bgc1, Bgc2 denote two horizons with similar morphologies, but at different depths from the paleosol surface.
² Mineralogical composition of bulk fraction as determined from powder X-ray diffraction. M = Montmorillonite; K = Kaolinite, I = Illite, and S = Siderite.