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The presence of two normal faults at one dam foundation is inferred from regional geology. Locally, the foundation rocks around and between the fault suspected zones are covered by thick deposits of gravely Sand with boulders and sandy Silt soils. Unfortunately, exploratory core holes drilled did not cross the fault planes but entails some of their effects.
Now, it is required to determine the exact position (orientation and width) of the fault zones to design appropriate foundation treatment measures before starting construction. Which geophysical technique do you think is best to apply to this problem? All propositions/answers are valuable. Thank you.
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It appears to me that the previous answers relate to each responder’s pet technique.
The question was, “Now, it is required to determine the exact position (orientation and width) of the fault zones to design appropriate foundation treatment measures before starting construction.
A three-dimensional seismic survey designed to focus on very shallow horizons with geophone locations closely spaced, and utilizing a high-frequency energy source will answer the question.
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In some stratigraphic section, quartzites represents the UNCONFORMITY LEVEL or basement.
Could anyone recommend me some "reference studies/review papers" that explain "why quartzites represent the unconformities"?
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Well, I'd say that, generally, quartzites do not represent unconformities. However, on a global evolutionary scale, it could be that before terrestrial plants evolved, one could imagine land surface as exposed igneous/metamorphic rocks with no vegetation to trap the finer particles on-land. Therefore, much of the surface (at this time) could have been composed of SiO2 aeolian dunes. If this were the case, your argument might hold up for quartzites older than terrestiral plants (700 Ma) and directly overly basement.
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The paleostress orientations inferred from the orientations of dikes (see attached figure) indicate that none of the principal stress axes is oriented at neither vertical nor horizontal orientation, rather all of them are oriented at the intermediate orientation between the vertical and horizontal orientations. Hence, the fact violates the Anderson theory of faulting, where one of the principal stress axes must be vertical due to the stress boundary condition at the surface of the earth.
What could be the plausible explanation?
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Anderson's Theory assumes one of the principal stress axes to be vertical as the earth's surface (i.e. air) has no shear stress (like every fluid). Only normal stress is acting. Thus, the theory is only applicable at the earth's surface, not in deeper parts of the crust (where shear stress increases).
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According to my knowledge Landslides start from a tension crack and propagate along a critical slip surface. There are circular, non-circular etc.. various kinds of slip surfaces, i would like to know how we can guess the type of slip surface based on regional geology and geotechnical properties. Can someone point me to specific publications that are well known in this regard?
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First, you should develop a conceptual model to understand what kind of materials and what kind of controls are acting on your slope instability.
1) you should define the type of landslide you expect: shallow landslide within the soil cover? large bedrock slide? Relatively shallow earthslide? For each typology, the shape and the location of slip surface can be different (for instance, for shallow landslides within soil cover we usually assume the failure parallel to the slope, located at the soil-bedrock contact).
2) you should make a hypothesis (that you'll demonstrate or not) on the geological control. Is the slide occurring on fractured bedrock? In this case, the slip surface is controlled by the joints. Is the slide occurring on soil or extremely fractured rocks (according to the scale of the landslide)? In this case, the slip surface can be circular, sub-circular or logarithmic spiral. Is the slide occurring on layered materials? In this case, different layers can control the slip surface.
3) you should finally evaluate other possible controls, such as groundwater level, slope morphology, the presence of tension cracks on the top, water seepage, geological structures (faults, major discontinuities), etc.
Once you have developed your conceptual model, you can run numerical simulations with either a stress-strain approach or a limit equilibrium approach, as Kreuzer commented above. However, if you don't have a clear conceptual model of teh landslide and a good geological model, you would spare time with millions of useless attempts.
Regarding the literature, it's huge, but you should direct your search to the appropriate type of landslide and type of materials.
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How long do echinoderms (specifically crinoids) live?
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In my paper in Palaeontology in 1986, on pseudoplanktonic fossil crinoids, I found growth lines on brachial plates that suggested that benthic isocrinids reached full size in just 4 or 5 years while the pseudoplanktonic pentacrinitids grew significantly faster and attained a similar size (arm length of about 10-15cm) in just 2 or 3 years. Download the paper at http://www.habitas.org.uk/staff/staff_pdf_files/Simms%202.pdf
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I am currently doing a research on the boundary between Zimbabwe craton and Limpopo belt mainly focusing on the Northern marginal zone. Does anyone have suggestion of articles or rather have a different perspective on the events that took place, I mean the different subdivisions of the Limpopo belt consist of different ages. For example the the Central zone shows ages of around 2 Ga whilst the southern marginal zone shows both 2Ga and dominantly 2.7Ga not quiet sure about the Northern marginal zone. What does this mean, Or maybe the Zimbabwe craton collided with something first before ?
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Another key reference should be that of Blenkinsop 2011 in the GSA special volume. Search for it online with this reference.
Blenkinsop, T.G., 2011, Archean magmatic granulites, diapirism, and Proterozoic reworking in the Northern Marginal Zone of the Limpopo Belt,  Geological Society of America Memoir 207, p. 1–24, doi:10.1130/2011.1207(13).
David
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Having in mind the prevalence of most agglutinated foraminifera during this event.
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Hi, have a look at dinoflagellate cyst literature. Although you will not find many cysts in the salt deposits you will find distinct assemblages for both low and high salinity environments just prior to, during and just after the crisis. Here are some references I have in my database to start with:
Santarelli, A. Brinkhuis, H. Hilgen, F. J. Lourens, L. J. Versteegh, G. J. M. and Visscher, H., 1998. Orbital signatures in a Late Miocene dinoflagellate record from Crete (Greece). Marine Micropaleontology 33, 273-297.
Popescu, S. M. Dalesme, F. Jouannic, G. Escarguel, G. Head, M. J. Melinte-Dobrinescu, M. C. Sütő-Szentai, M. Bakrac, K. Clauzon, G. and Suc, J. P., 2009. Galeacysta etrusca complex: dinoflagellate cyst marker of Paratethyan influxes to the Mediterranean sea before and after the peak of the Messinian Salinity Crisis. Palynology 33, 105-134.
Londeix, L. Benzakour, M. Suc, J. P. and Turon, J. L., 2007. Messinian palaeoenvironments and hydrology in Sicily (Italy): The dinoflagellate cyst record. Geobios 40, 233-250.
Louwye, S. de Schepper, S. Laga, P. and Vandenberghe, N., 2007. The Upper Miocene of the southern North Sea Basin (northern Belgium): a palaeoenvironmental and stratigraphical reconstruction using dinoflagellate cysts. Geological Magazine 144, 33-52.
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Do you recognize the chert structure in attached pdf from the early Eocene Rus Fm of Qatar, Middle East? Is it stromatolitic?
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Interesting photos and discussion.
Need to look at TS and CS in thin sections for texture and structure. as pointed out, the photos are insufficient to justify any concrete conclusion.
Possible options:
Hydrothermal vent deposits (observed in marine sediments deposited in proximity of volcanic vents where the gaseous fluids create tubular deposits of chert / carbonates with a concentric laminate pattern;
Ichnofossils - organic chert / calcite binding along tubular habitats of burrowing organisms - that leave behind such features
Simple fluid escape structures produced during lithification of silicic sediments under special conditions, where the fluids remain trapped in the lower strata and then are triggered into escape through tubular vents....(akin to mud-volcanoes)
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I am assuming that since these are found in sedimentary rocks, other processes should not be brought into consideration, although even biogenic superficial weathering by soil-dwelling burrowers could also yield such features.
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Does ridge push can reactivate oceanic fracture zones? 
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The answer given by Volker Kaminske is quite good, the oceanic lithosphere takes some 12-15 Ma to become brittle. But some precision should be made in the question issued by Carlos Ganade de Araujo itself. There's NO "MORB" lithosphere, MORB is a term specific for mid ocean ridge basalts, which make up oceanic crust, not lithosphere. The lithosphere under the oceanic crust  call the LID or oceanic mantle lithosphere, which comprises usually more than 90% of the thickness of an oceanic lithospheric plate, is not made of basalt, but of ultramafic rocks,such as peridotite, dunite and  pyroxenite, often serpentinized and tectonized.  
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What is the exploration history and structural evolution of the forth basin?
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i need information about
*regional geology
*tectonic settings and basin evolution
*petroleum system elements
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Amalgamated accumulations resulting from climatic and eustatic changes, Akchar Erg, Mauritania. GARY KOCUREK1, KAREN G. HAVHOLM1, MAX DEYNOUX2 and
RONALD C. BLAKEY3. Sedimentology Volume 38, Issue 4, pages 751–772, August 1991
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Part of my research is based on African Geology and so i would like to know if there's any information i can get on crustal formation and craton amalgamation in relation to Africa
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Journal of African Earth Sciencs
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I am working on a research paper on plutons, specifically the Sierra Nevada batholith region for geology and need good foundation articles.
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You can also check out our GSA field forum guide citing a lot of the literature on the SNB that is out there.