Geologic and biostratigraphic map of the Pierre shale in the Canon City-Florence Basin and the Twelvemile Park area, south-central Colorado

Biostratigraphy of the Campanian-Maastrichtian, Mid-Maastrichtian, and Cretaceous-tertiary boundaries in the Raton Basin: Implications for models of early Laramide tectonism and for the origin of the enigmatic Disturbed Zone

The Mountain Geologist ◽

10.31582/rmag.mg.53.2.75 ◽

2016 ◽

Vol 53 (2) ◽

pp. 75-91 ◽

Cited By ~ 1

Author(s):

Keith Berry

Keyword(s):

New Mexico ◽

High Resolution ◽

South Dakota ◽

Sedimentation Rates ◽

Southwestern Part ◽

Pierre Shale ◽

South Central ◽

Disturbed Zone ◽

History Of ◽

Differential Sedimentation

The Campanian-Maastrichtian stage boundary is placed within the upper part of the Pierre Shale about 100 m below the base of the Trinidad Sandstone at Berwind Canyon, Colorado. Correlation of ammonite biostratigraphy with palynostratigraphy places this boundary near the top of the Vermejo Formation in the southwestern part of the Raton Basin, northeastern New Mexico. The informal mid-Maastrichtian boundary should be placed at the level of the Trinidad Sandstone at Berwind Canyon, although it should be placed at the level of the Vermejo-Raton unconformity in northeastern New Mexico based upon palynostratigraphy. High-resolution megafloral biostratigraphy of the K-T boundary is also discussed. Chronostratigraphic and paleoenvironmental indicator species reveal differential sedimentation rates across the basin. The magnitude of the Vermejo-Raton unconformity varies primarily in a north-south direction across the Raton Basin and was greatest in northeastern New Mexico and least in south-central Colorado, which may affect interpretations of the early Laramide history of the Raton Basin. The results of this study preclude correlation of the basal part of the Vermejo Formation with the Disturbed Zone of southwestern South Dakota.

Download Full-text

Lithic geochemistry of the Claggett marine cyclothem in south-central Saskatchewan

Canadian Journal of Earth Sciences ◽

10.1139/e88-148 ◽

1988 ◽

Vol 25 (10) ◽

pp. 1554-1563 ◽

Cited By ~ 4

Author(s):

S. G. Whittaker ◽

T. K. Kyser ◽

W. G. E. Caldwell

Keyword(s):

Large Scale ◽

Volcanic Ash ◽

Sea Water ◽

Mineralogical Composition ◽

The United States ◽

Chemical Compositions ◽

Diagenetic Alteration ◽

Pierre Shale ◽

South Central ◽

Volcanic Debris

Sediments of the Lea Park Formation in south-central Saskatchewan were deposited in the Claggett sea during the Late Cretaceous (Campanian) Claggett marine cycle. Rocks of the Lea Park Formation have remained virtually unaffected by diagenetic alteration; hence, variations in mineralogical and chemical compositions result primarily from changes in the source of detritus. Quartz, feldspar, discrete illite, kaolinite, and chlorite were derived from weathering of the western highlands, whereas illite–smectite (I–S), the dominant clay phase, originated from volcanic ash. Changes in the proportions of these minerals suggest a large-scale volcanic episode during deposition of the Lea Park sediments, an episode that affected not only the detritus delivered to the seaway but also the chemical and isotopic compositions of the sea water itself. δ13C values of organic matter increase with little change in the quantity of organic carbon preserved through both the transgressive and regressive phases of the Claggett cyclothem, unlike other cyclothems in which δ13C values generally decrease through the regressive phase. The increase in δ13C values in the Claggett cyclothem suggests a partial contribution from volcanic emanations to the 13C/12C ratio of the sea. Dissolution of Mg-rich volcanic debris from a major volcanic episode resulted in anomalously high Mg/Ca ratios in the sea and in the shells of molluscs living in the sea at that time. Rocks containing the shells with anomalously high Mg/Ca ratios are not themselves unusually Mg rich, but a general increase in Mg/SiO2 ratios in the rocks points to an increase in volcanic influx. The similarity between the mineralogical composition of the Lea Park Formation in Canada and that of the coeval lower part of the Pierre Shale in the United States indicates that volcanic ash was an important detrital source for both formations.

Download Full-text

Principles of New Park-area Planning as Applied to the Wrangell-St Elias Region of Alaska

Environmental Conservation ◽

10.1017/s0376892900015162 ◽

1985 ◽

Vol 12 (1) ◽

pp. 59-66 ◽

Cited By ~ 2

Author(s):

R. Gerald Wright

Keyword(s):

Planning Process ◽

Multiple Use ◽

Data Types ◽

Planning Decisions ◽

South Central ◽

Ecological Principles ◽

Considerable Controversy ◽

Park Area ◽

Management Alternatives ◽

Area Planning

In an era of increasing land-use demands, it is getting ever-more-difficult to set aside lands for parks or equivalent units where protection rather than (multiple) use of the resource is the goal. Developing a sufficient justification for establishing an area of parkland is directly related to the proper use of well-recognized ecological principles—particularly to the fact that the area included should encompass a unique or nationally significant resource (Polunin & Eidsvik, 1979).This paper discusses four basic criteria that were used to evaluate potential boundary and resource-management alternatives for a seven-million-ha region in south-central Alaska, much of which was eventually included in the Wrangell-St Elias National Park and Preserve. The necessity or basing the planning decisions on sound data cannot be overemphasized. The paper discusses the different data-types used in the planning process. It was the feeling of all involved in the planning process that more was known about the natural and social resources of the new Alaskan parks than had been known about any other new areas that had been added to the system. The need for good data is particularly acute when the establishment of the parks involves considerable controversy and opposition, as was the case here.

Download Full-text