GLOBAL IMPLICATIONS OF THE N-ALKANES DISTRIBUTION IN THE NEGATIVE CARBON ISOTOPE SPIKE OF SEGMENT C2, EL PUI SECTION, ORGANYà BASIN, CATALUNYA, SPAIN
In the expanded El Pui section segment C2 precedes those assigned to anoxic event 1a (OAE 1a) (C3 – C6)  and is marked by a negative inflection of ~ 0.5 to 1.5 ‰, also present within that interval elsewhere (Tunisia, ; Cismon APTICORE, Italy, Santa Rosa Canyon, Mexico, . In addition to previous proxies [2 -3], n-alkanes were investigated to further characterize the depositional environment associated with this negative spike. The results are unvarying throughout, with dominance of calcareous nannofossils associated with a TIC average ~ 72.3 CaCO3 %, abundance of roveacrinid fragments, scarce minute planktonic foraminifera. The n-alkanes before the negative inflection shows that OM is mainly derived from protists and microbial sources, short-chain length homologues (≤ nC19) dominate the highest values. During the negative spike, the n-alkanes are predominantly short-chain length homologues with very little to no contribution from shallow marine (nC20 - nC25), land-derived aquatic vegetation, and absolutely none from higher plants (>nC25). The terrestrial/aquatic ratios TARs (nC27+nC29+nC31)/(nC15+nC17+nC19) averaging 0.36 before and 0 during the negative inflection imply that local factors did not enhance the 𝛿13Corg negative inflection during C2. Thus global factors such as clathrate destabilization [e.g. 6 - 7] and large igneous provinces (LIPs) may be invoked to cause similar negative shifts in the 𝛿13Corg curve [1 - 8].
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