Lignin phenol-based evidence of rapid 8 cm sediment deposition from a hurricane flooding event in continental margin San Blas Basin, Mexico

A 45 cm sediment core from San Blas Basin on the continental shelf of pacific Mexico, 50 km off the coast and north-west of Puerto Vallarta, was taken and analysed for lignin, a biomarker for terrestrial organic matter (TOM). The total amount of lignin phenols ranges between 1.5 to 4.5 mg lignin phenol/10 g sediment except for an order of magnitude increase between 18 cm and 26 cm which was 20 to 40 mg lignin phenol/10g sediment. Acid to aldehyde ratios of vanillin-type lignin (Ad/Al (v)), a proxy for degradation, had a range of 0.36 to 0.58 while the section between 18 cm to 26 cm was fresher with a range of 0.26 to 0.28. S/V to C/V analysis indicated that the lignin is sourced from angiosperms. The section between 18 cm to 26 cm had statistically similar values ranging between S/V of 0.85 to 0.95 and C/V of 0.19 to 0.21. S/V to Ad/Al (v) analysis had a negative slope indicating S-type lignin is preferentially degraded and the background lignin signal could look more like the fresher 18-26 cm section if degradation had not occurred. We conclude a large hurricane flooding event brought fresh TOM off of the land and the sediment deposition between 18 to 26 cm was deposited in one event due to the S/V and C/V values overlapping.