Пятница, 29.03.2024
Мой сайт
Меню сайта
Статистика

Онлайн всего: 1
Гостей: 1
Пользователей: 0
Форма входа
Главная » 2013 » Ноябрь » 27
 
STRATIGRAPHY (continued)

PALEOZOIC STRATA

BASIS FOR DIVISIONS USED

Exposures of Paleozoic strata are confined almost entirely to areas in the eastern part of the mountains of the Flathead region. The rocks in these areas consist of marine deposits of Cambrian, Devonian, and Carboniferous age that are northward extensions of units described and named by C. F. Deiss (1933, 1943b, p. 1129-1136, 1943a, p. 216-231). His nomenclature for Paleozoic strata in and west of the Saypo quadrangle is applicable in a general way to those of the Flathead region. Lateral changes appear to exist, but more intensive paleontologic and stratigraphic work are required before these can be evaluated. In any case, they could not be adequately shown on small scale maps such ... Читать дальше »
Просмотров: 636 | Добавил: rostowskaja | Дата: 27.11.2013


Lower part of the Missoula group on the ridge between the North Fork of Belly River and Mokowanis River



[From field notes by Eugene Stebinger and H. R. Bennett, Sept. 20, 1914]





























Feet

Purcell basalt.

Hornfels, deep-greenish, siliceous. A baked mud with contorted structure faintly visible, suggesting that the mud was disturbed by the passage over it of the lava that overlies it, hence the eruption of the lava took place under water10

Shale, green-gray to gray, calcareous 45

Shale, deep-maroon, somewhat calcareous ripple-marked, mud-cracked; with a few quartzite beds132

Shale, gray to dark-green-gray, calcareous; weathers buff147

Limestone, shaly, and shale, slabby gray to green-gray, thin-bedded; weathers buff; contains stromatolites158

Shale, deep-red, ripple-marked, mud-cracked59

Limestone, sh ... Читать дальше »

Просмотров: 620 | Добавил: rostowskaja | Дата: 27.11.2013

 
Siyeh limestone along Garden Wall from Collenia undosa zone in lower part of Missoula group down to Conophyton zone 1 in the Siyeh on Going-to-the-Sun Highway, about 7.7 miles west of Logan Pass

[Measured by Richard Rezak, 1951]


Feet
Collenia undosa Walcott, isolated heads. Laminae are pink; matrix is green argillite1
Argillite, alternating green, tan, and purple; finely laminated34
C. undosa, poorly developed heads, similar to those at top of section2
Argillite, alternating green, tan, and purple, finely laminated71
Argillite, alternating green, tan, and red, finely laminated. Contains irregular bands of calcareous, oolitic, white, pink, and green sandstone. Sandstone is commonly crossbedded and in lower 4 ft of unit contains pyrite cub ... Читать дальше »
Просмотров: 612 | Добавил: rostowskaja | Дата: 27.11.2013

 
Stromatolites have been recorded from the Grinnell argillite only in 2 localities: 1 along the Going to-the-Sun highway and 1 in Bad Rock Canyon. (Rezak, 1957, p. 136-137) This fact may aid in distinguishing its outcrops from otherwise similar exposures of the Missoula group in which stromatolites are far more abundant and easily recognized.

The Grinnell argillite is mostly in shades of red purple which, where of characteristic color, are distinctive enough to be recognized with confidence by anyone familiar with the formation. While the Missoula group also contains many red-purple beds, colors in that group approach reddish brown in hue. Typical beds in the Grinnell argillite are definitely more purplish than those typical of the Missoula, but the distinction is ... Читать дальше »
Просмотров: 810 | Добавил: rostowskaja | Дата: 27.11.2013 | Комментарии (0)

STRATIGRAPHY

OUTLINE OF MAJOR POINTS

The rocks of the two regions range in age from Precambrian to Recent. Most were deposited in shallow seas. In addition, there are extensive deposits of continental origin of several different kinds. The thickest units belong to the Belt series of Precambrian age. Study of these has contributed to revision of concepts as to the character and stratigraphy of the rocks of the series. The principal contribution, obtained through areal geologic mapping over a broad region, is the evidence of marked lateral changes within short distances. In the regions represented in plates 1 and 2 the exposed part of the Belt series is now regarded as consisting, in ascending order, of the Ravalli group, Piegan group, and Missoula group. Each of the groups comprises subordinate units but subdivision is incomplete at present.

Sufficient new information in regard to the stromatolite content of the rocks has been obtained to produce new concepts a ... Читать дальше »
Просмотров: 1184 | Добавил: rostowskaja | Дата: 27.11.2013 | Комментарии (0)

NOMENCLATURE OF THE RANGES

Geographic nomenclature, especially with respect to the mountain ranges, is in a state of confusion in the part of Montana with which this report is concerned. Few official decisions as to these names are available. The following summary cites the various names that have been applied to the mountain units, the history and authorities for use of these, and the limits within which each name appears to have been intended to be applicable. No new names are proposed.

The different mountain ranges described in the present report (pls. 1, 2, 3) collectively constitute a segment of the eastern part of the physiographic province termed "the Northern Rocky Mountains" (Fenneman, 1930). Within the United States his definition has received acceptance in official and general usage except for such modifications in detail as those of Freeman and his coworkers (Freeman and others, 1945, p. 56; Caldwell, 1954, p. 79-87). A different definition was proposed e ... Читать дальше »
Просмотров: 674 | Добавил: rostowskaja | Дата: 27.11.2013

Geological Survey Professional Paper 296

Geology of Glacier National Park And the Flathead Region, Northwestern Montana  http://www.nps.gov/history/history/online_books/geology/publications/pp/296/abstract.htm
 
GEOLOGY OF GLACIER NATIONAL PARK AND THE FLATHEAD REGION NORTHWESTERN MONTANA

By CLYDE P. ROSS

This report summarizes available data on two adjacent and partly overlapping regions in northwestern Montana. The first of these is Glacier National Park plus small areas east and west of the park. The second is here called, for convenience, the Flathead region; it embraces the mountains from the southern tip of Glacier Park to latitude 48° north and between the Great Plains on the east and Flathead Valley on the west. The fieldwork under the direction of the writer was done in 1948, 1949, 1950, and 1951, with some work in 1952 ... Читать дальше »
Просмотров: 760 | Добавил: rostowskaja | Дата: 27.11.2013 | Комментарии (0)

Geological Survey Professional Paper 296

Geology of Glacier National Park And the Flathead Region, Northwestern Montana
 
 
POST-BLACKFOOT EROSIONAL FEATURES



Although the Blackfoot surface may have reached its culmination as recently as the early part of the Pleistocene epoch, it has since been attacked so vigorously that in many places its remnants have not been identified with assurance. Only the major features of the somewhat complex post-Blackfoot history are known. Those features related primarily to stream erosion are described here; features of glacial origin being touched upon in later pages.



After the Blackfoot surface was formed, rejuvenation took place, and streams cut deep valleys in the mountains, reducing the nearby plai ... Читать дальше »
Просмотров: 827 | Добавил: rostowskaja | Дата: 27.11.2013 | Комментарии (1)

 
 
GEOMORPHOLOGY

GENERAL FEATURES OF THE GEOMORPHOLOGY

The deformation that reached a climax in the Lewis overthrust was followed by uplift and accelerated erosion early in Tertiary time. The major structural features trend northwest and had a marked effect on the development of the initial drainage pattern. Erosion by the streams thus started has produced ranges and groups of ridges with trends that are influenced by structure. The steep faults that border several of the ranges made great contributions to outlining the mountain masses. Irrespective of whether these faults are normal or reverse, they constitute large, persistent fractures ... Читать дальше »
Просмотров: 546 | Добавил: rostowskaja | Дата: 27.11.2013

Glacier National Park. Geology

INTERPRETATION OF THE STRUCTURE

GENERAL STRUCTURAL FEATURES

In the foregoing, available data in regard to the structural features present are summarized. Much remains unknown or obscure, but enough facts have accumulated to form a basis for discussion and to cast serious doubt on some of the concepts suggested by previous workers, who were under the disadvantage of having only the results of preliminary reconnaissances to work with. The concepts advanced below constitute attempts at interpretation of the observed structural features. Speculations as to the fundamental reasons for the formation of the structural features involve consideration of the origin and constitution of the earth and are beyond the scope of this report.

The accumulation of great thicknesses of sedimentary r ... Читать дальше »
Просмотров: 575 | Добавил: rostowskaja | Дата: 27.11.2013

Glacier National Park. Geology

INTERPRETATION OF THE STRUCTURE

GENERAL STRUCTURAL FEATURES

In the foregoing, available data in regard to the structural features present are summarized. Much remains unknown or obscure, but enough facts have accumulated to form a basis for discussion and to cast serious doubt on some of the concepts suggested by previous workers, who were under the disadvantage of having only the results of preliminary reconnaissances to work with. The concepts advanced below constitute attempts at interpretation of the observed structural features. Speculations as to the fundamental reasons for the formation of the structural features involve consideration of the origin and constitution of the earth and are beyond the scope of this report.

The accumulation of great thicknesses of sedimentary r ... Читать дальше »
Просмотров: 522 | Добавил: rostowskaja | Дата: 27.11.2013

 
 
MOUNTAIN-BUILDING STRUCTURAL FEATURES

In the Paleocene or somewhat afterwards, conditions changed drastically from those outlined above. Broad warpings of the earth's crust so gentle that the resulting structural features have to be inferred rather than seen were succeeded by violent movements in which the rocks were tightly folded and eventually extensively fractured. Thrusts and normal faults of the first magnitude resulted from a series of earth movements that have not entirely ceased even yet. In the summary that follows, the structural feature ... Читать дальше »
Просмотров: 590 | Добавил: rostowskaja | Дата: 27.11.2013

Поиск
Календарь
«  Ноябрь 2013  »
ПнВтСрЧтПтСбВс
    123
45678910
11121314151617
18192021222324
252627282930
Архив записей
Друзья сайта
  • Создать сайт
  • Официальный блог
  • Сообщество uCoz
  • FAQ по системе
  • Инструкции для uCoz
  • Все проекты компании
  • Copyright MyCorp © 2024
    Бесплатный хостинг uCoz