Open AccessDirect evidence for the alteration of 13 C natural abundances during early diagenesis in Lake Kasumigaura, Japan
Author(s) -
Kohzu Ayato,
Imai Akio,
Ohkouchi Naohiko,
Fukushima Takehiko,
Kamiya Koichi,
Komatsu Kazuhiro,
Tomioka Noriko,
Kawasaki Nobuyuki,
Miura Shingo,
Satou Takayuki
Publication year - 2011
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2011gc003532
Subject(s) - diagenesis , geology , δ13c , sediment , sediment trap , isotopes of carbon , stable isotope ratio , isotope , sedimentary rock , sedimentation , sedimentary organic matter , total organic carbon , organic matter , geochemistry , oceanography , environmental chemistry , mineralogy , paleontology , chemistry , physics , organic chemistry , quantum mechanics
In sediment trap materials or suspended particulate organic matter, δ 13 C values must be averaged over at least several years to determine δ 13 C shifts during sedimentation. To overcome this problem, we studied isotopic modification of sedimentary organic carbon during early diagenesis in sediment samples collected intermittently from a site at the center of Lake Kasumigaura, Japan, over a period of nearly 30 years, beginning in 1979. We examined the degree of apparent isotope discrimination by comparing long‐term changes in the carbon isotope composition of the surface sediment (top 2 cm) with the isotope composition profile from 0 to 15 cm. The downcore C isotope composition profile was close to the values calculated from the long‐term changes in the isotope composition of the surface sediment, suggesting that the sedimentary carbon isotope composition was generally conserved (±0.6‰) during early diagenesis (up to 30 years). However, at greater core depths, significant 13 C enrichment of up to 1.5‰ was sometimes observed, especially in the periods of relatively oxidative conditions.