Peak ratio values in unburied and buried leather samples. amide I/II: difference in wavenumbers between highest absorbance at ∼1620 cm⁻¹ and ∼1535 cm⁻¹.

		Amide A/amide I	Amide I/amide II	1450/amide III	1620/1650	1630	1535	ΔI/II
Unburied leather samples	Min	0.6	3.1	0.9	1.1	1612	1530	58
	Mean	0.8	7.2	2.0	1.2	1616	1539	77
	Max	1.1	20.4	4.9	1.4	1618	1560	88
	Range	0.5	17.3	4.0	0.3	6.0	30.0	30
Experimentally buried	Min	0.4	1.7	0.4	1.0	1618	1503	57
	Mean	0.7	8.8	1.2	1.2	1619	1540	79
	Max	0.9	30.7	3.7	1.7	1630	1560	112
	Range	0.5	29.0	3.3	0.7	12	55	55
Archaeological samples	Min	0.6	3.1	0.0	1.0	1618	1517	58
	Mean	0.8	4.2	0.8	1.1	1623	1543	79
	Max	1.5	8.9	3.2	1.1	1628	1560	105
	Range	0.9	5.8	3.2	0.1	10	43	47