Sediment maturity

Radke J, Bechtel A, Gaupp R, Piittmann W, Schwark L, Sachse D, Gleixner D (2005) Correlation between hydrogen isotope ratios of lipid biomarkers and sediment maturity. Geochim Cosmochim Acta 69 5517-5530... 

The Lixian Depression, some 500 km south of Xi an, is filled by about 10,000 m of Palaeozoic and Mesozoic sediments. Mature source rocks occur throughout the stratigraphic sequence, but the complicated geological structure has impeded exploration and there are as yet no commercial discoveries of oil or gas. Located in southern China, the region has a very wet climate and is largely covered by rice fields, so that soils in the region are invariably moist. 

Growth faulted deltaic areas are highly prospective since they comprise of thick sections of good quality reservoir sands. Deltas usually overlay organic rich marine clays which can source the structures on maturation. Examples are the Niger, Baram or Mississippi Deltas. Clays, deposited within deltaic sequences may restrict the water expulsion during the rapid sedimentation / compaction. This can lead to the generation of overpressures. 

Ablage, /. laying down storage place, depot, ablagem, v.t. i. deposit store age, mellow, mature, season. — v.t. deposit, settle, subside. Ablagerung, /. deposit deposition sediment ... 

Although the data are not plentiful, it is clear that the hydrothermal solutions of sediment-hosted ridges and back-arc basin covered by sediment (Okinawa Trough) contain high amounts of ammonium (2.8-13.6 p.molal) (Scott, 1997). This means that ammonium was derived by thermal maturation reaction of organic matter in sediments by the following reactions (Gamo et al., 1991),... 

The mechanism of alkyl hydrogen exchange was not clarified, but a possible mechanism was postulated. Partial hydride abstraction by a Lewis acid site may have occured forming a carbocation-like species followed by exchange of a proton at a R-carbon. Such a mechanism predicts exchange to occur preferentially at methyl groups adjacent to the most stable carbocations (benzylic > 3° > 2° > 1°). This is consistent with the observed relative rates of epimerization of steranes during thermal maturation of sediments (83). 

DDT converts in part to p,p -DDE over time in the environment, especially in sediments [151, 171]. An example of the total aliphatic extract of a sediment from the Los Angeles Bight contaminated with p,p -DDE is shown in Fig. 11. The TIC trace shows a major UCM and the minor resolved peaks are normal alkanes (primarily from higher plant wax), with mature 17a(H),21/ (H)-hopanes (from petroleum residues as is the UCM). The mass spectrum ofp,p -DDE is shown in Fig. 12a, registering the molecular ion cluster at m/z 316-320. DDE is detected in the m/z 246 fragmentogram (Fig. lid), appearing as a small peak in the TIC trace and DDT is not detectable in this sample. 

The HS yields from the pelletal and matricial OM (Table 1) shows a high content of humic compounds isolated from pellets (humic carbon up to 75% of TOC) and a lower one in adjacent sediments (humic carbon less than 21% of TOC), along with the higher content of HU (low mature kerogen) in surrounding sediments and the lowest in the pellets. 

Si02/Al203 ratios for the samples are high (average 10.0), and indicate a high degree of maturity of the sediments (Asiedu et al. 2000). 

Transcription is catalyzed by DNA-dependent RNA polymerases. These act in a similar way to DNA polymerases (see p. 240), except that they incorporate ribonucleotides instead of deoxyribonucleotides into the newly synthesized strand also, they do not require a primer. Eukaryotic cells contain at least three different types of RNA polymerase. RNA polymerase I synthesizes an RNA with a sedimentation coef cient (see p. 200) of 45 S, which serves as precursor for three ribosomal RNAs. The products of RNA polymerase II are hnRNAs, from which mRNAs later develop, as well as precursors for snRNAs. Finally, RNA polymerase III transcribes genes that code for tRNAs, 5S rRNA, and certain snRNAs. These precursors give rise to functional RNA molecules by a process called RNA maturation (see p. 246). Polymerases II and III are inhibited by a-amanitin, a toxin in the Amanita phalloides mushroom. 

The hopane series are the natural product biomarkers elucidated initially as attributable to bacteria.The 17a(H),2ip(H)-hopanes ranging from C27 to C35 (no C28) were encountered in numerous ancient sediments and petroleums, and diagenesis and maturation of the microbial precursors (e.g. bacteriohopanepolyol and diploptene, Fig. 4) were elucidated. The diagenesis of diploptene in contemporary sediments proceeds by double bond migration from via to... 

Simoneit BRT, Lipid/bitumen maturation by hydrothermal activity in sediments of Middle Valley, Leg 139, in Mottl M, Davis E, Fisher A, Slack] (eds.). Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 139, College Station, TX Ocean Drilling Program, pp. 447- 65, 1994. 

The dramatic changes in haze particle size seen with alterations in protein-to-polyphenol ratio in a model system, would, if this also occurs in real beverages, have profound effects on both sedimentation (e.g., cold maturation in a tank or centrifugation) and filtration operations. 

Bustin, R. M. Wust, R. A. J. 2003. Maturation, organic. In Middleton, G. V. (ed) Encyclopedia of Sediments and Sedimentary Rocks. Kluwer Academic Publishers, Dordrecht, 424-429. 

Xia and Ball (1999) measured sorption isotherms for a series of chlorinated benzenes and PAHs for an aquitard material (foc = 0.015 kg oc kg-1 solid) from a formation believed to date to the middle to late Miocene. Hence, compared to soils or recent sediment POM, the organic matter present in this aquitard material can be assumed to be fairly mature and/or contain char particles from prehistoric fires. A nonlinear isotherm was found for TeCB (fitting Eq. 9-2) and the following Freundlich parameters were reported XreCBF = 128(mg g 1)(mg mL 1) "T CBand "TeCB = 0.80. For partitioning of TeCB to this material (linear part of the isotherm at higher concentrations), the authors found a Kioc value of 4.2 x 104 L kg oc. 

Eukaryotic ribosomes contain four pieces of RNA (Tables 5-4 and 29-1), which are usually designated by their sedimentation coefficients. Tire 18S, 5.8S, and 28S RNAs are encoded as single transcriptional units with spacers separating the sequences that encode the mature RNAs. A typical animal cell contains several hundred copies of this transcriptional unit, all located in the DNA in the nucleolus (Fig. 28-15), and each having its own set of promoter sequences, enhancers, and transcription factors.47 520 522 The promoter sequences vary substantially among different species.523 The primary transcripts from these units are the sole product of RNA polymerase I. 

Summarizing the maturation process we can observe that thermal influences commence with the initial compaction of the sediments, and in the early stages decarboxylation and hydrogenation are the main reactions. Continued burial increases thermal cracking, and true petroleum development commences—first with the heavy oils rich in ONS compounds. Deep burial causes increased splitting of C-C bonds, isotopic... 

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