scholarly journals Acid-insoluble residue/carbonate content of the Upper Cretaceous Niobrara Formation, Berthoud field, Denver basin, Colorado; a key factor for understanding natural fracturing in chalks?

1991 ◽  
Author(s):  
R.M. Pollastro
Keyword(s):  
Upper Cretaceous ◽  
Insoluble Residue ◽  
Carbonate Content ◽  
Niobrara Formation ◽  
Denver Basin ◽  
Key Factor

The first record of spiral coprolites from the Dinosaur Park Formation (Judith River Group, Upper Cretaceous) southern Alberta, Canada

1995 ◽  
Vol 69 (6) ◽  
pp. 1191-1194 ◽  
Author(s):  
Clive E. Coy
Keyword(s):  
North America ◽  
Upper Cretaceous ◽  
First Record ◽  
Niobrara Formation ◽  
Southern Alberta ◽  
Dinosaur Park Formation

Spiral coprolites from the Upper Cretaceous of North America are poorly known. Enterospirae (fossilized intestines) reported from the Upper Cretaceous Niobrara Formation of western Kansas (Stewart, 1978) were disputed by McAllister (1985), who felt they represented spiral coprolites similar to those described from the Permian by Neumayer (1904). Previously described coprolites from the Upper Cretaceous of Alberta are small, unstructured, ellipsoidal forms thought to derive from a crocodilian or terrestrial, carnivorous reptile of necrophagic or piscivorous habits (Waldman, 1970; Waldman and Hopkins, 1970).

The type section of the Codell Sandstone

2021 ◽  
Vol 58 (3) ◽  
pp. 211-248
Author(s):  
James Hagadorn ◽  
Mark Longman ◽  
Richard Bottjer ◽  
Virginia Gent ◽  
Christopher Holm-Denoma ◽  
...  
Keyword(s):  
Surface Expression ◽  
Potassium Feldspar ◽  
Detrital Zircons ◽  
Niobrara Formation ◽  
Denver Basin ◽  
Fine Grained ◽  
Type Section ◽  
Fossil Fish ◽  
Fish Teeth ◽  
Reference Section

We formally assign, describe and interpret a principal reference section for the middle Turonian Codell Sandstone Member of the Carlile Shale near Codell, Kansas. This section, at the informally named Pumpjack Road, provides the thickest surface expression (9 m, ~30 ft) of the unit in Ellis County. The outcrop exposes features that typify the Codell throughout the southern Denver Basin and vicinity. At this reference section, the Codell conformably overlies the Blue Hill Shale Member of the Carlile Shale and is unconformably overlain by the Fort Hays Limestone Member of the Niobrara Formation or locally by a thin (<0.9 m, <3 ft) discontinuous mudstone known as the Antonino facies. The top contact of the Codell is slightly undulatory with possible compaction features or narrow (<30.5 m, <100 ft), low-relief (0.3-0.6 m, 1-2 ft) scours, all of which hint that the Codell is a depositional remnant, even at the type section. At Pumpjack Road, the Codell coarsens upward from a recessive-weathering argillaceous medium-grained siltstone with interbedded mudstone at its base to a more indurated cliff-forming muddy, highly bioturbated, very fine-grained sandstone at its top. The unit contains three informal gradational packages: a lower Codell of medium to coarse siltstone and mudstone, a middle Codell of muddy coarse siltstone, and an upper muddy Codell dominated by well-sorted very fine-grained sandstone. The largest grain fractions, all <120 mm in size, are mostly quartz (40-80%), potassium feldspar (7-12%), and albite (1-2%), with some chert (<15%), zircon, and other constituents such as abraded phosphatic skeletal debris. Rare fossil fish teeth and bones also occur. Detrital and authigenic clays make up 9 to 42% of the Codell at the reference section. Detrital illite and mixed layer illite/smectite are common, along with omnipresent kaolinite as grain coatings or cement. As is typical for the Codell, the sandstone at the type section has been pervasively bioturbated. Most primary structures and bedding are obscured, particularly toward the top of the unit where burrows are larger, deeper and more diverse than at its base. This bioturbation has created a textural inversion in which the larger silt and sand grains are very well sorted but are mixed with mud. Detrital zircons from the upper Codell are unusual in that they are mostly prismatic to acicular, euhedral, colorless, unpitted, and unabraded, and have a near-unimodal age peak centered at ~94 Ma. These characteristics suggest they were reworked mainly from Cenomanian bentonites; their ultimate source was likely from the Cordilleran orogenic belt to the west and northwest.

Geochemical aspects of the Santonian Chalk of Ramsgate, England, and the origin of the chert and clay minerals

1979 ◽  
Vol 43 (325) ◽  
pp. 159-164 ◽  
Author(s):  
D. A. Spears
Keyword(s):  
Clay Minerals ◽  
Upper Cretaceous ◽  
Major Element ◽  
Clay Content ◽  
Carbonate Content ◽  
Element Geochemistry ◽  
Carbonate Sedimentation ◽  
Volcanic Debris ◽  
The Mean

SummaryThe mineralogy and major-element geochemistry of thirty-seven samples from a borehole in the Upper Cretaceous Chalk (Santonian) of Kent has been determined. The mean carbonate content is 97% and the carbonate is a low-Mg calcite (0.42 mol % MgCO3). Most of the silica is deduced to be biogenic chert. The total clay content probably varies through the sequence due to changes in the rate of carbonate sedimentation. The clay composition remains relatively constant with smectite more abundant than illite. The smectite and K-feldspar could be formed from volcanic debris whereas illite and quartz are thought to be detrital.

Sign in / Sign up

Export Citation Format

Share Document