Tectonic Division Research Articles

A review of the Cambrian of China

Abstract The sedimentary history and biostratigraphy of China during the Cambrian Period are broadly discussed within the framework of major tectonic divisions of the country. Five platform domains (North China Platform, southwest China Platform, Chiangnan Belt, Tarim Platform, and Tsaidem Platform) and five eugeosynclinal belts (South Tibet‐western Yunnan Belt, Tienshan‐Altai‐Great Khingan Geosyncline, Chilian Geosyncline, Kunlun‐Tibet‐western Yunnan Geosyncline and Southeast China Geosyncline) are recognised and discussed individually. A zonal scheme for Chinese Cambrian biostratigraphy is provided and the problems of the Precambrian to Cambrian, Cambrian to Ordovician and also the series boundaries are discussed. International correlation of the Cambrian of China, especially with Australia, is outlined in some detail.

Seismic reflection measurements of Southwest Japan Margin

Data from continuous seismic reflection profiles made across the continental margin on the Philippine Sea side of southwest Japan are used to build on previous studies. The general distribution and trend of various submarine structural units are shown with respect to major tectonic divisions on land. The continental slope has two sections, an upper slope and a lower slope separated by a closely spaced series of sediment-filled basins at intermediate depths. They are parallel to the regional trend of the province and located off large embayments in the coast. The seaward limb of each basin is a sedimentary ridge whose convex side faces the Philippine Sea. At the foot of the lower continental slope is a narrow furrow, called the Nankai trough, which in part may be a developing trench. The intermediate-depth basins, including the outer ridge parts, and the Nankai trough are structurally related units and are analogous to features found west of central Luzon, Philippines.

Geological study of the Hida metamorphic belt in the eastern part of Toyama Prefecture, Central Japan (Part 1):On the tectonic division, the characteristics of the Funatsu stage plutonism, and the lithostratigraphic division of the metamorphic rocks

Geological study of the Hida metamorphic belt in the eastern part of Toyama Prefecture, Central Japan (Part 1):On the tectonic division, the characteristics of the Funatsu stage plutonism, and the lithostratigraphic division of the metamorphic rocks

The Devonian history of northeastern Australia

Abstract Devonian rocks occur in northeastern Australia within the ‘Tasman Geosyncline’ in three major tectonic divisions—(a) a very broad mobile platform related to the last stages of stabilisation of the Lachlan Geosyncline, marginal to which is found, (b) the volcanic‐rich New England Geosyncline, and (c) a contrasting region in northern Queensland where complex marine to continental sedimentation occurred on cratonic blocks while non‐volcanic flysch‐like sedimentation occurred in the marginal Hodgkinson Basin. The tectonic setting was governed by differences in the nature of the continental margin, so that the New England Geosyncline and Hodgkinson Basin, which developed along the eastern margin of the continent from the earliest Devonian to the late Palaeozoic, show correspondingly different sedimentation and deformation histories. An integrated account of the Devonian geology of these regions is given, leading to.an interpretation of the environments of the Devonian in terms of plate‐tectonic moveme...

Cretaceous Deltas, Alberta: ABSTRACT

End_Page 871------------------------------Tectonic divisions of the Precambrian basement of Alberta seem to have exerted geographic control on the emplacement of major deltas of the late Mesozoic. The greater thicknesses of the Albian lower Blairmore delta coincide with the site (in Devonian time) of the west Alberta ridge and the Peace River high. The thick parts of the latest Cretaceous Belly River and Edmonton deltas show similar disposition. The Dunvegan delta (Cenomanian) pinches out abruptly south of the Peace River arch. The Milk River delta (Campanian) is a feature of the Sweetgrass arch and the lower Edmonton tongue is limited to an area west of the same arch. Hydrocarbon pools within these deltas are controlled by pre-Cretaceous erosion features and/or by shoreline facies. End_of_Article - Last_Page 872------------

Western Cordillera--Alaska to Mexico: ABSTRACT

There are three longitudinal divisions of the western cordillera: the Coast Range belt along the Pacific margin, the Nevadan belt next inland, and the Laramide belt, farthest inland. A fourth tectonic division is superposed on parts of the Nevadan and Laramide belts: the Basin-Range system. Ancestral to these Mesozoic and Cenozoic mountain systems was a late End_Page 1900------------------------------ Precambrian and Paleozoic geosyncline with marginal eugeosyncline and inward miogeosyncline divisions. The Antler orogenic belt of central Nevada evolved in Mississippian and Pennsylvanian times, and thenceforth clearly separated the eugeosyncline from the miogeosyncline. The Ancestral Rockies as range-size uplifts in Colorado, Utah, Arizona, and New Mexico also came into being during Pennsylvanian time. Deformational and igneous phases in the eugeosyncline after the Antler orogeny continued until the climactic phase in mid-Cretaceous time. Then, most of the voluminous batholiths were emplaced. With the batholiths and the deformed and metamorphosed eugeosynclinal sediments, the Nevadan belt had been brought into being. In Alaska, the Nevadan belt makes up the Alaska and associate ranges from the Yukon Valley to Cook Inlet. In British Columbia, the Interior Plateaus, the Coast Range, and the island ranges comprise the Nevadan belt. In the western United States it extends from western Nevada through the Sierra Nevada of California to the Coast Ranges. In fact, the basement of the Coast Ranges is a Nevadan complex. The core of the Nevadan belt extends the length of the peninsula of Baja California. The miogeosyncline and an adjacent belt of the shelf were deformed in Cretaceous and early Tertiary times to form the Laramide Rockies. In Alaska the Brooks Range, as a geanticlinal uplift, and the fold system of the Yukon Valley constitute the Laramide Rockies. The Canadian Rockies and Foothill or Disturbed belt extend the Rockies into Montana. In the western United States two divisions of the Rockies occur: the ranges caused by deformation of the miogeosyncline, and the ranges created by deformation of the shelf. A complex system of folds and thrusts characterizes the miogeosyncline division, whereas individual elongated uplifts with intermontane basins characterize the shelf. The writer resolves the folds and thrusts of the miogeosyncline into gravitational glide structures margina to several primary uplifts, and into shallow compressional structures between the uplifts, but other geologists do not share this view. The Laramide Rockies extend into central Mexico, principally as a fold system. The Cenozoic Era in the western cordillera was a time of extensive volcanism and tensional faulting. The two are so closely related temporally and spatially that they must be related genetically. The faulting created the Basin-Range system and the Rocky Mountain trench. Most of the Basin-Range province is laden with volcanics, and among the numerous volcanic fields is the great Sierra Madre Occidental of Mexico and the basaltic extrusions of the Cascades and the Columbia River Plateau. The Pacific margin of Mexico and the United States is being deformed by major strike-slip faults, with the Pacific block moving northwest. End_of_Article - Last_Page 1901------------

The Facies Front of the Devonian Slave Point-Elk Point Sequence in Northeastern British Columbia and the Northwest Territories

Abstract The facies front of the Slave Point – Elk Point sequence is the narrow zoneof contact between the carbonate Slave Point, Sulphur Point and Pine Pointformations and the equivalent shales of the Horn River formation. The faciesfront trends approximately north-northeast in British Columbia andeast-northeast in the Northwest Territories. The shales lie to the northwest ofthe front and the carbonates to the southeast. The facies front of the Slave Point Elk Point sequence is in the order of 1000 miles in length. It extends over a maximum known stratigraphic interval ofabout 1,300 feet. In parts of the Northwest Territories, the interval overwhich the facies front is developed is considerably less due to the influence of a positive tectonic feature known as the Tathlina High. In most areas, the Slave Point and Sulphur Point formations pass to shalequite abruptly and tend to behave as a unit in this respect. The zone in whichthe Pine Point formation passes to shale is much broader than that in which the two overlying formations pass to shale. Three main tectonic divisions of the facies front are recognized. It is probable that the major morphological features of the front result from structural control. Drilling has shown that, in many areas, the dolomitized Slave Point formation at the facies front contains abundant reserves of natural gas. There are sufficient grounds for believing that the underlying formations at the front also contain significant hydrocarbon reserves. Introduction In the eastern part of northeastern British Columbia and in northern Alberta, the Slave Point Elk Point sequence consists of a series of evaporites and carbonates, mainly Givetian in age. When traced to the northwest, the evaporites are lost from the sequence and the Slave Point – Elk Point rocksconsist of a series of limestones and dolomites with occasional interbedded shales. Beyond a relatively narrow zone of profound lithologic change whichtrends east-northeast across the southern part of the Northwest Territories and north-northeast across northeastern British Columbia, the upper three-quarters of the Slave Point – Elk Point sequence is represented by a series of shales.

A.A.P.G. Basement Project: ABSTRACT

The Basement Rock project of the A.A.P.G. was initiated in the fall of 1956; it is supported from the Research Fund. The Basement Project Committee, organized on a geographic basis, is currently compiling a basement map of North America between 24° and 60° N. Latitudes. This map will consist of two parts: (1) a map showing basement wells with code number, outcrops of basement rocks differentiated as to age and gross lithology, and contours on the basement surface and (2) a geologic and structural map of the basement. Preliminary copy for (1) is nearly complete. This map will be published through the cooperation of the U. S. Geological Survey and will be accompanied by a text giving basic data for all wells. Basement studies are important in regional evaluations. Knowledge of basement geology and structural grain aids in interpretation of geophysical data. Movements along basement structures produce structures in younger basin rocks which can be prospected more effectively if the basement control is recognized. Basement topography controls the facies of overlying sedimentary rocks. A regional knowledge of basement terranes is valuable in determining source of sediments and direction of transport. In areas where basement rocks are not granite, thousands of unnecessary feet of hole have been drilled into metasedimentary and volcanic rocks. In some areas fractured basement rocks are reservoirs. Petrographic methods, supported by geophysical and other information, can, within the limits of well control, establish (a) major lithologic and tectonic features such as orogenic belts, volcanic terranes, plutonic terranes, and fault zones and (b) tectonic divisions within concealed orogenic belts, such as allocthonous plates, belts characterized by different type and degree of metamorphism, and zones of igneous activity. End_of_Article - Last_Page 1249------------

Introduction to Tectonics of Rocky Mountains: ABSTRACT

The Rocky Mountain system extends from the Liard River, B. C., to Santa Fe, New Mexico, and is the dominant geological feature within the seven-state Rocky Mountain section. Five tectonic divisions based on the present structural position of the Precambrian crystalline basement exist within the system and the adjacent eastern area. The divisions are: Canadian shield; thinly covered shield; area of locally exposed basement; area of deeply buried basement; and the area where the basement is no longer recognizable. End_Page 785------------------------------ Precambrian rocks exposed over large areas of Canada collectively form the Canadian shield. The exposed basement is bounded in Alberta and Saskatchewan by overlying sediments. The surface upon which the overlying sedimentary rocks were deposited is warped into a major syncline the steeper limb of which lies in or near the disturbed belt of Alberta and Montana and along the Rocky Mountain front. In this syncline the basement is covered by a relatively thin veneer of sediments except for local areas such as the Williston basin. Petroleum accumulation in the area of thin sedimentary cover is controlled more by stratigraphic than by structural factors. The area of local exposure of the Precambrian basement includes the Southern Rockies, the Wyoming basin, and part of the Middle Rocky Mountain province. Prior to deformation the basement was thinly covered by sediments. Anticlinal mountain ranges and deep local intermontane basins characterize the region. The site of deformation was localized by the Pennsylvanian structural history. Petroleum accumulation is largely controlled by geologic structure. The Precambrian basement was deeply depressed beneath the troughs existent in central Utah, western Wyoming, eastern Idaho, western Alberta, and eastern British Columbia during late Precambrian and early Paleozoic time. Deformation of the troughs created the overthrust belt characterized by repetition of the sedimentary sequence in overthrust fault plates. Absence of Precambrian basement rocks in the thrust plates suggests that faulting is localized in the sedimentary sequence. Accumulation of petroleum have been negligible in this division. The Precambrian basement complex is no longer recognizable in the areas of batholithic intrusion in Idaho, Montana, and British Columbia. The development of granite and granite gneiss in the Idaho batholith, age 100 MY, modified the pre-existing rocks, and substituted a new floor for subsequent geologic history. Lineaments of primary significance are superimposed across the tectonic divisions. The lineaments have complex geologic histories in which transverse movement was probably important. The prominent lineaments are: Rocky Mountain trench, Montana lineament, Wyoming lineament, and the Walker lineament, all of which separate regions of differing geology. Volcanically derived materials of Cenozoic age are widely spread across the Rocky Mountain system, and reflect igneous activity of great magnitude. Extensive tectonic adjustment took place by means of normal and reverse faulting both during and subsequent to the deposition of the volcanic products. The extent and magnitude of the late Cenozoic faulting are as yet incompletely understood. Critical discrimination should be made between fault systems of different ages. End_of_Article - Last_Page 786------------

Tectonics of Colorado Plateau: ABSTRACT

The Colorado Plateau structural province consists of seven principal basins, nine principal uplifts, and several intermediate tectonic divisions such as platforms, slopes, sags, and broad saddles. Long monoclinal flexes between uplifts and basins are the principal lines of deformation in and marginal to the Plateau. The Plateau may be divided roughly into northeastern and southwestern parts which differ considerably as to the magnitude and form of the principal tectonic elements. The northeastern part includes the major basins (Uinta, Piceance, and San Juan), the Paradox fold and fault belt, and uplifts End_Page 789------------------------------ and monoclines that generally face southwesterly. The southwestern part includes the minor basins (Henry, Kaiparowitz, Black Mesa, and Blanding), the broad Mogollon slope, and uplifts and monoclines that generally face eastward. The salt anticlines, piercements, and graben of the Paradox basin are the most special structures of the Plateau. Their folding and piercement began in Permian time, continued intermittently through Triassic and Jurassic time, and culminated in Laramide time. Subsequent collapse may be partly related to Cretaceous loading, partly to Laramide folding, and partly to solution of the salt. In addition to the elongate, tangentially compressed uplifts such as San Rafael, Circle Cliffs, or Zuni, there are several domical uplifts due to the stock and laccolithic intrusions such as the La Sal, Abajo, or Ute centers. These centers fall on three nearly parallel, northwesterly trending lines. The earliest tectonic events that appear to have influenced the present structure occurred during late Paleozoic time. Three northwesterly trending Permo-Pennsylvanian positives developed on and adjoining the Plateau. From northeast to southwest, these are the Front Range, Uncompahgre, and Zuni. All appear to have been asymmetrical toward the southwest where they were immediately adjoined in order by the Colorado, Paradox, and San Juan sags or basins. During Triassic and Jurassic time, local folding occurred in the Paradox fold belt and elsewhere and broad, slight epeirogenic sagging developed in a northwesterly direction between the Uncompahgre and Zuni positives. In late Jurassic time, the southern rim of the Plateau was generally tilted northward. During late Cretaceous time, the P ateau was markedly depressed and slowly tilted northward as it became a part of the Rocky Mountain geosyncline. Despite the fact that the descriptive tectonics of the Plateau are fairly well known, there still remain several problems concerning the cause, nature, and history of deformation and the character, nature, and history of fluid movement. Among these problems are (1) influence of the Precambrian structures on later deformation, (2) Paleozoic and Mesozoic diastrophisms as interpreted from stratigraphy, (3) cause and nature of Laramide movements especially in relation to the formation of the adjoining Rockies belts, (4) significance of the fracture systems, (5) Cenozoic erosional history and basin sedimentation, and (6) paleodynamics of the rock fluids. End_of_Article - Last_Page 790------------

Tectonic Divisions of North America

Tectonic Divisions of North America