Discussion on “A rapid loess flowslide triggered by irrigation in China” by D. Zhang,G. Wang,C. Luo,J. Chen,and Y. Zhou

Catastrophic debris flows hit many areas in the world. Surprisingly, the features of the materials which are involved are often very similar as well as the causes of rupture and the mechanics of resulting movement. A continuous exchange of ideas among people involved in studies and investigations could be highly beneficial in the setting up of reliable criteria for risk mitigation.     

Replies to Comment by K. Bratvedt,E. Bølviken,T. Gimse,H. Holden,L. Holden,and R. Knarud

Mathematical Geosciences -     

Characterization of melanoidins by IR spectroscopy—I. Galactose-glycine melanoidins

A comparative IR spectral study was conducted with synthetic melanoidins which were prepared from various ratios of sugars and amino acids and a pseudomelanoidin which was prepared from sugar only. A significant resemblance was observed between the pseudomelanoidin and the melanoidin prepared from a high (9:1) sugar ratio (type 1). Another series of melanoidins (type 2) consists of those prepared from an “excess” of amino acid (9:1 and 1:1).Type 1 showed the presence of carbonyl and hydroxyl groups as well as aromatic vibrations. The same groups were detected in the spectrum of the pseudomelanoidin. These features were observed in a very low concentration in the type 2 melanoidins.Carboxylic groups are present in pseudomelanoidin and in both types of the melanoidins. However, the acid strength of this group is high in melanoidin of type 2, but low in type 1 and in the pseudomelanoidin.The nitrogen atom which is involved in the melanoidin structure is present as a tertiary amine.Heat treatment of KBr discs containing glycine, galactose and a mixture thereof revealed that galactose was converted into pseudomelanoidin; a mixture of galactose-glycine yielded the corresponding melanoidin of type 2; no reaction was observed with glycine.     

Reply to Comment by Z. Şen,İ. Sönmez,and H. Tatli

Mathematical Geosciences -     

Reply to D. F. Lascelles. Discussion on ‘Microplaty hematite—its varied nature and genesis’ by R. C. Morris and ‘Genesis modelling for the Hamersley BIF-hosted iron ores of Western Australia: a critical review’ by R. C. Morris and M. Kneeshaw

Abstract

The third (Es₃) member of the Eocene Shahejie Formation is the main hydrocarbon source rock interval in the Raoyang Sag of the Bohai Bay Basin. The lower Es₃ (Es₃^L) and upper Es₃ (Es₃^U) submembers display clear differences in source rock quality. The formation mechanisms of the source rocks are investigated via geochemical methods using 60 samples from three wells to reconstruct the paleo-environment during deposition. The major element parameters exhibit changes in paleoclimate from humid to arid. Indicators such as Sr/Ba, B/Ga, the gammacerane index and isotopic data suggest fresh–brackish and hydrological open lakes with unstable water column stratification likely occurred during deposition of the Es₃^L submember and saline and hydrologically closed lakes with stable water column stratification likely during deposition of the Es₃^U submember. Carbon isotope values of organic matter, trace elements and biomarker parameters suggest that the Es₃^L submember had moderate productivity, with a significant contribution from terrigenous organic matter whereas the Es₃^U submember had slightly enhanced productivity, with no or minor contributions from terrigenous organic matter. Furthermore, the pristane/phytane ratio and the enrichment of Mo and U indicate that the euxinic bottom-water conditions (sulfidic) of the lakes during deposition of the Es₃^U submember were best for preserving organic matter. Comparison of the models of source rock deposition of the Es₃^L and Es₃^U submembers indicates that the redox conditions play an important role in the formation of organic-rich source rocks in the Raoyang Sag.