Coals Cretaceous

The Angiosperms evolved in the Cretaceous, and from that period on the coals were formed from floras much like those we see today. In any period, the floral origin of the coals in one basin was not necessarily precisely the same as that of coals formed in other basins at the same time. 

The solubilities thus recorded for 13 Western (Cretaceous) coals (with 69.6-91.5% carbon, daf) and 8 Carboniferous coals (80.6-90.9% C, daf) are shown in Figure 1, and indicate that... 

What is, however, still unclear is whether these effects arise solely from different chemical compositions (and molecular configurations) or are also, at least in part, a consequence of the Cretaceous coals generally containing almost twice as much mineral matter as the Carboniferous samples. 

Figure 1. Solubilities after treatment with tetrahydronaphthalene at 390°C for 4 hr (----------------), cretaceous coals (-), carboniferous coals.

Black coal. Black coal ranges from Cretaceous age (65 to 105 million years ago) to mid-Permian age (up to 260 million years ago). They are all black some are sooty and still quite high in moisture (sub-bituminous coal). A common name for this coal in many parts of the world is "black lignite. Coals that get more deeply buried by other rocks lose more moisture and start to lose their oxygen and hydrogen they are harder and shinier (e.g., bituminous coal). Typical energy contents are around 24 to 28 MJ/kg. These coals generally have less than 3% moisture, but some power stations burn coal at up to 30% ash. 

Fig. 1. CO2 and methane sorption isotherms for the Lower Cretaceous Mannville Group high volatile bituminous B coal, Alberta. 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

Figure 5. Softening and fusion appearance a) vitrinite enriched cretaceous LVB at 330 " C b) completion of fusion (422 " C) for a vitrinite enriched cretaceous LVB coal.

Berkowitz, N. Fryer, J.F. Ignasiak, B.S. Szladow, A.J. Behaviour Differences Between Carboniferous and Cretaceous Bituminous Coals of Similar Rank. Fuel, 1974, (2), 141. 

Figure 5. The increase of rank of coal (on the basis of vitrite analyses) towards the magnetic anomaly near Bramsche. kru = Weatden (Lower Cretaceous) kroi = Cenomanian krot = Upper Campanian (Upper Cretaceous). The numbers at the margin of the map indicate the numbers of the single topographic maps 1 25 000...

Two diamond drill cores, designated DDH-A and DDH-B were obtained from central Colorado. DDH-B is from the vicinity of Redstone, Gunnison County, and core DDH-A is from the vicinity of Somerset in Delta County. These samples were particularly interesting since there is a transition from unaltered high volatile bituminous coal to natural coke at the igneous contacts. Both cores are of Cretaceous age coal. All core samples are from depths in excess of 1500 feet below the surface. 

The coal-bearing Cretaceous formations of the Verkhoyan area are 400-500 m thick in platform areas and over 2500 m thick in the foredip. In the foredip they extend from the north to southeast for more than 1500 km. Laumontite occurs only in the foredip in sandy packets, 20-100 m thick. Laumontite is absent in platform sections however, in some of them, Ca-zeolites, such as heulandite, desmine, and probably epistilbite, have been found. Although laumontite is widespread throughout the entire Cretaceous formations of the foredip, zeolites in platform sections are rare and have been found mostly in northern regions (19,20). 

During the Cretaceous period which dates back approximately 100 million years. Deposits include the predominately bituminous and sub-bituminous coal beds in the Rocky Mountain Province, extending in large, separated regions from central Montana into northeastern Arizona and northwestern New Mexico. 

In the subsurface, arsenic may readily accumulate in coal. Specifically, groundwater percolating through volcanic deposits may leach arsenic and transfer it to underlying coal beds during or after coalification. Contact metamorphism and any associated hydrothermal fluids are other processes that sometimes locally enrich arsenic in coal seams. At a site in British Columbia, a Cretaceous bituminous coal seam was contact metamorphosed by a mafic dike. The contact temperatures were about 700-900 °C, which could volatilize arsenic and/or dissolve it into associated hydrothermal fluids. The arsenic was then transported and deposited into cooler sections of the seam (Yudovich and Ketris, 2005), 163. 

Figure 1. Atomic H/C vs. O/C ratios for asphaltenes from a variety of sources (M) petroleum crude (Alberta, Cretaceous, Carboniferous, and Devonian) ( ) Middle East crude (w) North and South American crude (+) shale oil (+) oil sands and (A) liquids from Kentucky coal at 4000 psi hydrogen and West Virginia coal at (O) 4000 psi, and (U) at 2000 psi hydrogen (21)...

Most coal-derived liquid hydrocarbon deposits are of Late Cretaceous or Tertiary age. Only four known deposits are of Paleozoic age (Clayton, 1993). The age distribution of coal-derived petroleum does not correspond to the worldwide age distribution of coal deposits (Figure 3), as —60% of the world s coals are Permian or older (Bouska, 1981). Evolutionary changes in the biopolymers characteristic of vascular plants may have contributed to the greater abundance of coal-derived petroleum from Late Cretaceous and younger coals. 

Meissner F. F. (1984) Cretaceous and lower Tertiary coals as sources for gas accumulations in the Rocky Mountain area. In Hydrocarbon Source Rocks of the Greater Rocky Mountain Region (eds. J. Woodward, F. F. Meissner, and... 

Fig. 2-26. Results obtained by the CHIM method over an oil deposit in Byelorussia and schematic geological section 1- Permian-Cretaceous-Quatemary clays, sands, coals 2- marly siliceous clay formations 3- Carboniferous sand-clay formations 4- middle-late Devonian sandstones, aleurolites, marls 5- oil deposit (reproduced with permission from Ryss et al., 1990).

The Australian Torbanite is an algal shale discussed by Hatcher et al. (12), the Cretaceous black shale is discussed in Dennis et al. (24), and the Waynesburg log is a coalified log from the Connellsville Sandstone Member ofthe Conemaugh Formation, which has a rank of high-volatile A bituminous coal (R. Stanton, personal communication). (fa denotes carbon aromaticity.)... 

In simple terms ash partings are relatively abundant in Cretaceous and Tertiary coals of the West and rare in Carboniferous coals of the East. We are less certain of the Gulf Coast Tertiary lignites but they appear to have at least a moderate abundance of... 

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