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Foraminifera have an evolutionary history that extends back to the Cambrian, more than 525 million years ago. Since then, they have radiated and evolved. To date, approximately 60,000 fossil and modern species have been validly recognized (LANGER, 2011), and an estimated 10,000 species (including only 40-50 planktonic species) are still living (VICKERMAN, 1992), constituting the most diverse group of shelled microorganisms in modern oceans (SEN GUPTA, 1999). These small-sized organisms, usually 0.1 to 1 mm, may be very abundant, and tens of thousands living specimens per square meter may be found in some environments (WETMORE, 1995). Their mineralized tests (shells) usually get preserved in the sediment after the death of the organism and may constitute a major, sometimes the dominant, part of many modern or fossil sediments (fig. 1). They are easy to collect, and their high-density populations provide an adequate statistical base, even in small volume samples, to perform environmental analyses, making them a powerful tool for environmental assessment. <...>
Geologists, also known as Geoscientists, are trying to understand the constitution of the earth. The surficial portion, which is directly visible to the geologists, is made up more of water bodies (the seas, the oceans, and the lakes, together constitute nearly 2/3rds of the entire surface of the earth) than the land masses (Africa, America, Asia etc.). Large area of land around the north and the southpoles, is covered with a thick blanket of ice sheet, throughout the year.
The Earth is approximately spherical, with a mean radius R = 6370km, a very small flattening (+7/ − 15km), mass 6 × 1024kg, and an average density 5.5g/cm3; the law of gravitational attraction is F = GmMr/r3, where F is the force directed along the separation distance r between two point bodies with mass m and M; and G = 6.67 × 10−8cm3/g · s2 is the gravitation constant.
The history of life is written in the rocks, or more precisely in the fossils contained within the rocks. Fossils are the remains of ancient animals and plants, as well as fungi and microbes, preserved by natural processes of burial and entombment. Without the existence of fossils it is doubtful whether Charles Darwin would ever have devised his theory of evolution by natural selection.
Oui choice of title for this book deliberately echoes Dseison’s A Hillary ofBritiih Earthquake!, which was published by the Cambridge University Press early in the 1920s. This was one of the first in recent tiroes to make a systematic study of seismic activity in a particular country, which we have tried to emulate for Iran. By calling our study a history we wish also to emphasise the importance оf time in the unfolding of geologic processes, and of investigating the past when attempting to under-&tand the present.
The concept of reciprocal space is over 100 years old and has been of particular use for crystallographers to understand the patterns of spots seen on a detector when x-rays are diffracted by crystals. However, it has a much more general use, especially in the physics of the solid state. In order to understand what it is, how to construct it, and how to make use of it, it is first necessary to start with the so-called real or direct space and then show how reciprocal space is related to it. Direct space describes the objects we see around us, especially regarding crystals, their physical shapes and symmetries, and the arrangements of atoms within: the so-called crystal structure. eciprocal space, on the other hand, deals with the crystals as seen through their diffraction images. Indeed, crystallographers are accustomed to working backward from the diffraction images to the crystal structures, which we call crystal-structure solution. In solid-state physics, one usually works the other way, starting with reciprocal space to explain various solid-state properties, such as thermal and electrical phenomena. <...>
Being able to accurately identify minerals in thin-section is an essential skill for any geologist, and is vital for the correct interpretation of rocks and their petrogenesis. It can be a particularly challenging prospect for students new to the subject. However, with a basic understanding of microscopy, petrology and optical mineralogy, coupled with some reference text books, it is soon possible to identify some of the major rock- forming minerals with confidence.
