Fossil remains

Calcium, as noted above, is the fifth most abundant element in the earth s crust and hence the third most abundant metal after A1 and Fe. Vast sedimentary deposits of CaC03, which represent the fossilized remains of earlier marine life, occur over large parts of the earth s surface. The deposits are of two main... 

Th ese manufactured light sources are, perhaps ironically, largely dependent on the Sun. The radiant energy from the Sun has been stored in the fossilized remains of billions of creatures over millions of years and is used to power the electric light sources created by modern humans. The power generated by hydroelectric sources also is a result of solar evaporation and subsequent rainfall. Only nuclear reactors provide power independent of the Sun, which is, of course, the largest nuclear reactor in the solar system. 

There are a few developments on the horizon that will increase our ability to date bones and teeth reliability. Both y- and a-spectrometric methods can measure Pa/ U and °Th/U and concordance between dates calculated using the two can provide a measure of reliability. However, the discordance between the two is not very sensitive to different uptake regimes, and it is difficult to resolve, for example, bones that have undergone EU from those that have undergone LU with the analytical errors commonly encountered in measurements by y- and a-spectrometry. On the other hand, it has been shown recently that TIMS can measure both isotopic ratios with a precision usually better than 1% (Edwards et al. 1997). TIMS measurements of Pa/ U and °Th/U have yet to be routinely applied to dating fossil remains, but in the future, concordance between the two decay series will provide further evidence of the validity of a particular uptake model to a particular sample. 

Stromatolites Domal concretions formed on the seafloor, primarily shallow waters, by microorganisms. These deposits represent the oldest unequivocal fossilized remains of life on Earth. 

This book is designed to provide an all encompassing vision of the diversity of natural products in the perspective of biodiversity. Both living organisms and fossil remains are taken into account, without any bias for either the sea, land, or extreme environments. Understandably, however, this is not intended to be a comprehensive portrait of natural product diversity, which would be beyond my resources and would demand a multi-volume treatment. 

These are processes where a certain set of biodiversity disappears, leaving space for another set. Abundant fossil remains speak for the turnover of species. What happet to natural products is more difficult to appreciate because fossil molecules are only rarely found, or have suffered from diagenetic transformations. 

Fossil molecules and past natural product diversity Fossil remains as old as 3,000 My have been found of the precursors of modem cyanobacteria. The oldest remains of eukaryotes date to 2,500 My. Thus, together with many other landmark findings, the history of fossil remains is illustrative of the past events, in particular mass extinctions, which are dramatic episodes of biodiversity loss from unusual causes. 

Radioactive elements are ones in which the atoms break up, changing into atoms of other elements. The time taken for half the original element to disappear is called the half-life. The man-made element fermium has a half-life of 80 days. Thus, if a gramme of fermium were made today, less than one-sixteenth of a gramme would be left at the end of a year. The half-life can be very useful. By measuring the amount of radioactive carbon left in fossil remains, or other matter that was once alive, scientists can determine their age. 

Although calcium is more metallic in character than magnesium, compounds of the two elements share some similar properties. Calcium carbonate, CaC03, occurs naturally as chalk and limestone. Marble is a dense form of calcium carbonate that can be given a high polish it is often colored by impurities, most commonly iron cations (Fig. 14.26). The two most common forms of pure calcium carbonate are calcite and aragonite. All these carbonates are the fossilized remains of marine life. Calcium carbonate decomposes to calcium oxide, CaO, or quicklime, when heated ... 

There is also the chance that calcareous, phosphatic, and siliceous fossil remains are products of metasomatosis. 

Conclusively, the material is characterized by an N-linked aromate, which, together with additional aliphatic and aromatic structures, and probably under participation of sulfur and phosphorus, composes complex molecules. In the exterior sheath of the microspheres, dolomite is indicated by the lines at 1100, 725 and 300 cm-1. A weak line at 1445 cm-1 might belong either to dolomite or to a C—H deformation (Pflug et al., 1979)117) (Fig. 34). There is scarcely any doubt that the detected organic substances represent decomposed and fossilized remains of cell material. 

Similar to other cosmogenic radionuclides 14C is produced by reaction of cosmic rays with atmospheric atoms such as N2 and O2. Living plants and animals in the biosphere contain a constant level of l4C however, when they die there is no further exchange with the atmosphere and the activity of 14C decreases with a half-life of 5730 40 y this provides the basis for establishing the age of archeological objects and fossil remains. 

Coal is die compressed and dehydrated fossilized remains of plants. These materials are classified by some as sediments, even though they are composed largely of organic compounds. Coal is discussed in detail as an organic sediment in Chapter 2. 

Fossil remains of a deep subsurface biosphere are unequivocal traces of former deep life, as contamination via drilling or mining procedures can be excluded. However, traces of fossilized eukaryotic life in deep subterranean environments are extremely rare (Schumann et al., 2004). There are fossil representatives of all known domains of life, and while fossilized fungi do exist, they are exceptionally rare. The standard paleo-botanical literature refers to the lack of fossil records of fungi (Pia, 1927 Gothan Weyland, 1964 Pirozynski, 1976). 

Dating of the sedimentary and, indeed, the record of other types of rocks for the pre-Phanerozoic or Precambrian essentially requires use of radiochronologic methods. In portions of the Precambrian, notably the latter part, fossil remains of algae and bacteria have been useful in certain cases. For most of the Precambrian, however, radiochronology is essentially the only useful method. Harland et al. (1990) reviewed Precambrian radiochronology and ages of Phanerozoic rocks. 

The six deposits have many characteristics in common. The fossil remains include a mixture of large and small mammals, small birds, small reptiles, and aquatic vertebrates. The bones and teeth of megavertebrates deposited amongst stream cobbles are relatively unworn, suggesting little transportation. Most of the sediments are an inhomogeneous mixture of large and small vertebrate remains, stream cobbles, clays, and cavities. None are stratified and yet all seem to be fluvial deposits. Most are poorly packed with inter-... 

The unusually high number of preserved MIS 5 sites (several orders of magnitude higher than expected) requires unusual conditions of preservation. In view of the fossil assemblage and the nature of the sediments we suggest that the catastrophic floods created extraordinary conditions for preservation of fossil remains and that they have not been destroyed because no comparable floods have occurred since last interglacial times in these caves. 

North America experienced the sea washing over its boundaries many times during the three billion-plus years of its Archean and Proterozoic history. Life had flourished in the shallow tidewater. Algae, a long-term resident of North America, was joined later by worms and other soft-bodied animals. Little is known of early soft-bodied organisms, because they left no skeletons to become fossils. Only a handful of good fossils remain from the entire world s immense Precambrian rock record. 

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