GPS and Isotopic Data for Potomac River Samples used in Science Paper
Sample	Description *	Elevation	Easting	Northing	10Be activity			Model Age
ID		(masl)	(m)	(m)	(104 atoms g-1)			(ky) §
GF-21	PS/CHT	42	305651	4316940	17.8	±	0.6	37.1	±	3.9
GF-29	PS	39	305478	4317077	17.8	±	0.7	38.1	±	4.1
GF-32	PS	44	305331	4317611	18.8	±	0.7	38.8	±	4.2
GF-33	PS	47	304998	4318280	15.6	±	0.5	32.4	±	3.4
GF-40	PS	46	305164	4318186	18.2	±	0.6	37.5	±	4.0
GF-65	PS/GFT	43	304964	4318557	12.9	±	0.4	26.5	±	2.8
GF-37	PS	44	304792	4318599	12.5	±	0.5	25.5	±	2.7
GF-37X †	PS	44	304792	4318599	12.7	±	0.5	25.9	±	2.8
GF-46	PS	47	304991	4318736	14.9	±	0.5	30.2	±	3.2
GF-42	High PS	47	305258	4317839	26.8	±	0.9	55.7	±	5.9
GF-43	High PS	47	305230	4317859	25.6	±	0.8	52.9	±	5.6
GF-31	High PS	47	305394	4317349	37.5	±	1.1	77.9	±	8.3
GF-35	High PS	45	305372	4317142	36.8	±	1.2	76.3	±	8.1
GF-38	High PS	49	304740	4318427	41.7	±	1.3	85.6	±	9.2
GF-39	High PS	51	304765	4318443	30.3	±	0.9	61.7	±	6.5
GF-22	CHT	39	305663	4316947	11.6	±	0.4	27.7	±	3.0
GF-23	CHT	34	305664	4316954	9.37	±	0.3	22.8	±	2.4
GF-25	CHT	32	305681	4316952	8.88	±	0.4	20.0	±	2.2
GF-27	CHT	25	305674	4316965	7.59	±	0.3	16.9	±	1.9
GF-28	CHT	24	305650	4316970	5.82	±	0.3	12.7	±	1.5
GF-66	GFT	39	304941	4318549	7.59	±	0.3	15.5	±	1.7
GF-67	GFT	34	304932	4318542	3.72	±	0.2	7.6	±	0.8
* Abrieviations in the description field indicate from what part of Mather Gorge the samples were collected and/or what kind of analysis they were used for. PS=prominent strath level, High PS=moderately weathered high points on the prominent strath level, CHT=lower gorge (Cowhoof Rock) vertical transect, and GFT=Great Falls vertical transect. † GF-37x is an independently processed and measured laboratory replicate of GF-37. § Age uncertainties include propagated analytic errors (1 sigma) in carrier addition and AMS measurement, and +/-10% (1 sigma) uncertainty in 10-Be production rate.