Sediment burial history

In order to make sense of observed trends in sedimentary (C P)org ratios, and to evaluate the utility of this parameter in hind-casting past ocean productivity or in partitioning sedimentary organic matter as to source, it is important to understand the sources of organic matter to sediments, and the processes that modify the (C P)org ratio while organic matter is in transit to sediments, and then during its burial history. The (C P)org ratios of marine and terrestrial organic matter are distinct. This ratio in marine phytoplankton hovers closely around the classical... 

Ruttenberg K. C. and Goni M. A. (1997b) Depth trends in phosphorus distribution and C N P ratios of organic matter in Amazon Fan sediments indices of organic matter source and burial history. In Proc. Ocean Drilling Program. Sci. Res. (eds. R. D. Flood, D. J. W. Piper, A. Klaus, and L. C. Peterson), vol. 155, pp. 505-517. 

Another useful guide to the timing of cementation is estimation of the temperature of cementation from oxygen isotopic analysis and an assumed oxygen isotopic composition of. the pore water. From the temperature, cementation timing can be inferred from a time-temperature burial history. The present burial temperature defines the upper temperature limit of precipitation in much of the basin, where the sediment is currently at its maximum burial temperature. In the central basin, the pore water oxygen isotopic composition can be well constrained because only marine or evolved marine pore waters exist, and present-day values are known (Carothers Kharaka, 1978 Fisher Boles, 1990). For the central basin the pore water evolved from the initial Miocene marine value near zero (smow scale) to its present-day value near +4 (see Boles ... 

High cement volumes characterize many calcite cements from the basin margin sediments, and these presumably formed at shallow burial depths before significant compaction (Fig. 4E). Intergranular cement volumes are of the order of 30% to more than 40% in these samples. However, most cements from the basin margins have volumes indicating that they formed after some compaction and, like the central basin, cementation is a process that extends through much of the burial history (al-... 

Experimental compaction of sediments and modelling of chemical compaction may help to predict the physical properties of different lithologies as function of the burial history. This will provide a better basis for the interpretation of the seismic data (Fig 8). 

The thermal and burial histories of the basin for a variant that is free from erosion in the Permian were simulated for comparison with the main model (Fig. 6.7). This variant was controlled by present-day temperatures and vitrinite reflectance (similar to Fig. 6.6) and, by coincidence of the tectonic curve, calculated by removing the sediment and water load, resulting from variation in the thermal state of the basement (as... 

Measured TOC ranges from 2 to 8% in the Middle Devonian shales, and from 1 to 5% in the Late Devonian shales, but with maximum decreasing concentrations westward from 1.5 to 5.0% in the Illizi Basin, 1.0 to 3.5% in the Mouydir basin, and 1.0 to 1.8% in the Timimoune basin. These variations are likely linked to changes in transport direction and in the provenances of detritus as compared to Silurian shales. The level of organic matter maturation in the Devonian sources in these basins is higher (Ro = 1-4%) than it is in the equivalent sources of the Triassic province (Oued el-Mya, Ghadames, and Trias basins) due to differing sedimentation, burial, and tectonic histories. 

Dykstra J (1987) Compaction correction for burial history curves applications to Lopatin s method for source rock maturation determination. Geobyte 2(4) i6-z3 Espitalie J (1986) Use of as maturation index for different types of organic matter. Comparison with vitrinite reflectance. Therm. Model. Sediment. Basins. 1st IFP Explor. Res. Conf. Carcans. June 3-7, Paris, p 475-496... 

A concretion is a volume of sedimentary rock in which mineral cement fills the spaces between the sediment grains. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. Concretions form within layers of already-deposited sedimentary strata. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. 

Figure I. Elements of a Petroleum System. All petroleum systems contain 1. at least one formation of organic-rich sediments that has been buried to a sufficient depth by overburden rock such that petroleum is generated and expelled, 2. Pathways (permeable strata and faults) that allow the petroleum to migrate, 3. Reservoir rocks with sufficient porosity and permeability to accumulate economically significant quantities of petroleum, and 4. Sealing rock (low permeability) and structures that retain migrated petroleum within the reservoir rock. The top and bottom of the oil window is approximated as a function of burial depth. In actual basins, these depths are not uniform and vary as a function of organic matter type, regional heat flow from basement, in thermal conductivity of the different lithologies, and burial history (e.g., deposition rates, uplift, erosion, and hiatus events).

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