The precambrian rocks of ethiopia are important as they occupy the transition between the two structural and crustal domains of the east african orogen kazmin et al. Precambrian africa and south america as a single continent. Alkmim b, stephen marshakc aorogenic processes group, department of geology, university of leicester, leicester, le1 7rh, uk. The data come from many published 1d shear wave velocity. Precambrian geology of south west africa and namaqualand, precambrian research unit, university of cape town. Africa, the second largest continent, covering about onefifth of the total land surface of earth. The authors discuss the similarities and differences between the crustal blocks of the shield and incorporate details concerning geochemistry. Precambrian ironformations of southern africa economic.
West african proximity of the avalon terrane in the latest. Low latitude of deposition for late precambrian periglacial varvites in south australia. This large time span is difficult for humans tothis large time span is difficult for humans to comprehendcomprehend suppose that a 24hour clock representedsuppose that a 24hour clock represented all 4. Precambrian research 92 1998 251275 a structural transect across the coastal mobile belt in the brazilian highlands latitude 20s. Jelsma encyclopedia of life support systems eolss the worldwide 1. The precambrian is the least understood part of earth history, yet it. There are transitional areas between boreal and tundra flora. The precambrian encompasses the archean and proterozoic eons, which are formal geologic intervals that lasted from 4 billion to about 541 million years. The lower boundary of the canadian shield cuts across the province diagonally from the latitude 57 degrees in the north west to 54 degrees in the south east. In this book the editors strive to cover all primary i.
Consequent upon continued active field investigations and the advent of radioactive dating of samples from the area, the time is thought opportune to attempt a synthesis of precambrian correlations throughout west africa. The ages of these events, relative to the time scale, have been indicated, and it can be seen that there are no major gaps present, with all the eras in the precambrian and. Precambrian research publishes studies on all aspects of the early stages of the composition, structure and evolution of the earth and its planetary neighbours. Pdf precambrian mobile belts of southern and eastern africa. Seychelles, and our onshore geology to readily assess the geological context of the seeps.
Offshore stratigraphic columns of deep sea drilling sites in atlantic ocean 19681970. Developments in precambrian geology neoproterozoiccambrian. A structural transect across the coastal mobile belt in. Africas total land area is approximately 11,724,000 square miles 30,365,000 square km, and the continent measures about 5,000 miles 8,000 km from north to south and. Abstract this paper briefly summarises the geological and geomorphological history of south africa. Crustal structure of southern madagascar from receiver. Kroner and others published precambrian mobile belts of southern and eastern africa ancient. During the early paleozoic, the midatlantic region was near the equator and the mountain ranges. West africa is remarkable for its geological variety. Since then slow relative motion of nubian, arabian and somali plates over the same interval has been discerned. The downhole depths of the various sedimentary rock formations were picked by csd geologists for more than 19,000 deep wells. The precambrian is so named because it preceded the cambrian, the first period of the phanerozoic eon, which is named after cambria, the latinised name for wales, where rocks from this age were first studied. Palaeomagnetic evidence suggests that the principal cratonic areas of africa were approximately in their present relative positions and orientations as early as 2,200 m.
The dharwar craton, one of the parts of the indian shield, is estimated to be 3 billion years old one of the oldest continental fragments in the world. Image courtesy of the geological society of south africa. The geology of the country is the base for a large mining sector that extracts gold, diamonds, iron and coal from worldclass deposits. In siberia, southwest africa, and the arabian peninsula, the boundary is very close to 542 million years old. Although exposures of precambrian rocks in the usa are widely scattered, recent studies have provided much information about their subsurface distribution and tectonic history. Lower crustal exhumation under transtension during the. The study area belongs to the precambrian basement complex of southwestern nigeria which lies to the rest of the west african craton in the region of late. Contributions to the precambrian geology of southern. Seismic anisotropy, mantle fabric, and the magmatic.
It is the right size, not too small or too large if too small cant hold an atmosphere, if it is too large, it has too thick of an atmosphere so sunlight cant penetrate it and is in the optimal location from the sun temperature allows for water to exist. Pdf ghana is located along the gulf of guinea and atlantic ocean, in the subregion of west africa. We apply wellestablished discrimination systematics built on immobile. Palaeomagnetism of precambrian igneous and sedimentary. Panafrican, laurussian and pangean assemblies those of mantle plumes dominant since 200 ma. Second, the near bisection of the continent by the equator results in a largely symmetrical arrangement of. Both of these regions are mainly made of rocks that are either archean or paleoproterozoic in age, with western archean nuclei, and rock types are. As environmental concerns have become more prominent, the value of the geologist has not decreased, as they are still vital in locating and identifying the least intrusive methods of extraction.
However, the exploration and mining is much less mature in west africa than it is in other great precambrian gold provinces, with much of. This book surveys the precambrian geology of peninsular india and, to some extent, the himalayas. Precambrian crustal structure in africa and arabia. The east african rift system is increasingly viewed as a hydrocarbon exploration hotspot with recent discoveries in the albertine rift and offshore tanzania. Precambrian ice ages evidence for the earths oldest glaciers has been found in 2. The geology and engineering geology of roads in south africa paigegreen, p.
Frequency distribution of west african mineral deposits. With a focus on processoriented and comparative studies, it covers, but is not restricted to, subjects such as. Crustal scale transcurrent shearing in the paleoproterozoic sefwisunyani comoe region, west africa. Geologic setting of the study area the southwestern nigeria falls between latitude 7 0n and 10 0n and longitude 2 0e and 7 0e which is made up of rocks which are mainly precambrian in age. The gold endowment of the eburnean gold deposits, mainly orogenic type, equals that of the worlds other great precambrian lode gold provinces.
Oldest rocks studied are the orange river lavas 1850 my from which the three least altered sites give a vgp at 254 e, 19 n near the polar wander curve for africa at c. First, most of the continentwhich extends from 35 s to about 37 n latitude lies within the tropics. Africa itself is made up of several pieces of ancient continentcalled cratonsthat became stuck together many millions of years ago how ancient are they. Thus, the region contains pieces of islands, microcontinents, africa, and europe because of earlier collisions and. The changing latitude of the continents has controlled climatic changes. Pradhana, jonathan banksa, robert siriannia, misty strouda, brittany newsteada, jennifer gifforda a university of florida, department of geological sciences, 241 williamson hall, gainesville, fl 32611, usa bdepartment of geology, university of rajasthan, jaipur 302 004.
Paleomagnetic constraints on ages of mineralization in the kalahari manganese field, south africa. West african geology and metallogeny west african mineral deposit database metal endowment. The geology of south africa is highly varied including cratons, greenstone belts, large impact craters as well as orogenic belts. The geology and engineering geology of roads in south africa. One of the most fundamental enigmas of the earths palaeoclimate concerns the temporal and spatial distributions of precambrian glaciations. The southwestern nigeria falls between latitude 7 0n and 10 0n and longitude 2 0e and 7 0e which is made up. The precambrian lasted for more than 4 billionthe precambrian lasted for more than 4 billion years. Palaeomagnetic results are presented for a variety of precambrian rocks from southwestern africa. Most of africa is underlain by precambrian basement.
For best results viewing and printing pdf documents. Upper mantle structure of the saharan metacraton mohamed g. Tempos and events, in developments in precambrian geology 12. Geological interpretation covering somalia and west madagascar. Lowlatitude glaciation in the palaeoproterozoic era nature. The african upper mantle and its relationship to tectonics and. This old, but still common term was originally used to refer to the whole period of earths history before the formation of the oldest rocks with recognizable fossils in them.
Our location of avalonia in figure 8 contrasts with the reconstruction of nance and murphy 1994, 1996 fig. The cambrian period marks an important point in the history of life on earth. Africa geological interpretation study to also include the following updates. The canadian shield, precambrian shield, makes up the bedrock geology highlighted by rocks and lakes and a boreal forest area.
Some parts of the continent are over 3 billion years old, so they. Energy and mineral resources are vital to modern society, and it is the role of a geologist to locate these resources for human benefit. A number of factors influence the climate of the african continent. Precambriancambrian boundary at several places in the world contain tiny crystals of zircon. Balticaamazoniawest africa plate immediately prior to the onset of the development. Like most of africa, the region is largely composed of ancient precambrian rocks at least 541 million years old. The southwestern nigeria falls between latitude 7 0n and 10 0n and longitude 2 0e and 7 0e which is made up of rocks which are mainly precambrian in age. Late neoproterozoic and early cambrian palaeogeography.
Part or all of this report is presented in portable document format pdf. West african proximity of avalon in the latest precambrian those of the panafrican belts in west africa obrien et al. The precambrian or precambrian, sometimes abbreviated p, or cryptozoic is the earliest part of earths history, set before the current phanerozoic eon. We present here a global geochemical dataset from one hundredandfive greenstone sequences, ranging in age from the eoarchean through the archean and proterozoic eons that we have examined to identify different ophiolite types c. Precambrian research 224 20 11 22 table 1 summary of paleomagnetic results from the widgiemooltha dykes.
His example is a call, addressed to presentday geologists working on precambrian geology in africa and other regions, to consult the old colonial literature. These zircons have been carefully studied and dated using the idtims method. A list of the main geological and palaeontological events in south africa s geological history has been combined with the legend. The precambrian geology of south west africa and namaqualand. The precambrian geological record shows peak activity at. Seismic anisotropy, mantle fabric, and the magmatic evolution of precambrian southern africa paul g. A new edition of the geological map of africa at the 1. The basement complex of nigeria is polycyclic and retains memories of events dating back to about 3000 m.
Second, the near bisection of the continent by the equator results in a largely symmetrical arrangement of climatic zones on either side. Precambrian greenstone sequences represent different. Contributions to the precambrian geology of southern africa. As in other parts of africa, it suffered its most pronounced deformation and remobilisation during the pan african orogeny about 650450 m. Palaeomagnetic evidence suggests that the principal cratonic areas of africa were approximately in their present relative positions and orientations as early as.
Precambrian, period of time extending from about 4. Geology of west africa nd adjacent atlantic oceaf updated by lubomir jansa sources of information base map and major tectonic units on land taken from international tectonic map of africa 1968 1. This history is then related to various problems affecting the construction of roads in south africa. A structural transect across the coastal mobile belt in the. Abstract the precambrian rocks of madagascar were formed andor modified. The west african craton wac is one of the five cratons of the precambrian basement rock of. Palaeomagnetism of precambrian igneous and sedimentary rocks. Pdf presentation of the mamatwan and wessels paleomagnetic poles, implying stages of mn ore formation during orogenic events at. Developments in precambrian geology neoproterozoic.
This was the paleolithic period, the beginning of the study of geology and it goes back 2. The great lakes of africa and the red sea and dead sea in the middle east lie along new spreading centers. African geology at leeds university and the geological survey of malawi. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. However, the exploration and mining is much less mature in west africa than it is in other great precambrian gold provinces, with much of the development throughout the. Some parts of the continent are over 3 billion years old, so they are from the precambrian era. Some isotope age determinations would, at first glance, appear to necessitate radically new concepts of stratigraphic successions and correlations.
426 928 98 586 79 383 1398 490 254 1104 1110 29 624 1093 547 971 562 1378 744 1206 287 1240 1450 562 664 10 699 1116 750 45 5 920 888 1149 1468 1474 510 1154 222 89 888 601 193