Microfossils

Keywords d rec methods, indirect methods, rock properties, coring, core barrel, standard core analysis, special core analysis, slabbed core, sidewall samples, direct indications, microfossils, sonde, logging unit, invasion, mudcake, formation pressure measurement, fluid sampling, measurement while drilling, formation evaluation while drilling. 

SWS are useful to obtain direct indications of hydrocarbons (under UV light) and to differentiate between oil and gas. The technique is applied extensively to sample microfossils and pollen for stratigraphic analysis (age dating, correlation, depositional environment). Qualitative inspection of porosity is possible, but very often the sampling process results in a severe crushing of the sample thus obscuring the true porosity and permeability. 

Fig. 3-6 Microfossils of several filamentous microorganisms. Bitter Springs Formation, Central Australia. Dated at 0.85 Gyr. (Courtesy William Schopf.)...

Hofmann, H. J. and Schopf, J. W. (1983). Early Profer-ozoic microfossils. In "Earth s Earliest Biosphere, Its Origin and Evolution" (J. W. Schopf, ed.), pp. 321-359. Princeton University Press, Princeton, New Jersey. 

As noted already, intense submarine hydrothermal activity took place in the Japan Sea in 15-12 Ma, associated with Kuroko mineralization. However, it is uncertain that submarine hydrothermal activities associated with the Kuroko mineralization took place in the other periods from middle Miocene to present in the Japan Sea. Therefore, the geochemical features of sedimentary rocks which formed from the Japan Sea at these ages have been studied by the author because they are better indicator of age of hydrothermal activities than those of hydrothermally altered igneous rocks because the samples of continuous age of sedimentation are able to be collected and the ages are precisely determined based on microfossil data (foraminiferal, radioralian and diatom assemblages). 

Thick sedimentary pile from middle Miocene to late Pliocene is exposed in the Oga Peninsula, northern Honshu, Japan (Fig. 1.153). Age of the sedimentary rocks has been determined by microfossil data. Thus, the sedimentary rocks in the Oga Peninsula where type localities of Miocene sedimentary rocks in northern Japan are well exposed have been studied to elucidate the paleoenvironmental change of the Japan Sea (Watanabe et al., 1994a,b). Kimura (1998) obtained geochemical features of these rocks (isotopic and chemical compositions) and found that regional tectonics (uplift of Himalayan and Tibetan region) affect paleo-oceanic environment (oxidation-reduction condition, biogenic productivity). However, in their studies, no detailed discussions on the causes for the intensity and periodicity of hydrothermal activity, and temporal relationship between hydrothermal activity, volcanism and tectonics in the Japan Sea area were discussed. They considered only the time range from ca. 14 Ma to ca. 5 Ma. 

The Onnagawa Formation conformably overlies the Nishikurosawa Formation and is composed of siliceous shale and shale. The rocks are characterized by organic-rich laminated diatomaceous deposits, siliceous microfossils, and fish bones, while foraminiferal fossil is poor in amounts. The total thickness is about 3(X) m. The age of base of the Onnagawa Formation is estimated to be 12.9 Ma based on diatoms (Koizumi and Matoba, 1989). The age of the top of the Formation is 5.8 Ma. 

The Funakawa Formation conformably overlies the Onnagawa Formation. The thickness is about 1000 m. The Formation is composed of siltstone, intercalated by tuff and tuffaceous siltstone. Foraminiferal fossil and siliceous microfossil exist in the formation. 

Blow, W.H. (1969) Late middle Eocene to Recent planktonic foraminiferal biostratigraphy 1st International Conference on Planktonic microfossils. Proceeding, 1, 199 21. 

The early period of the Earth s history, around 3.8 1 billion years ago, is completely shrouded in darkness possible witnesses from this archaic period might help to cast some light. So we are looking for possible remains of the first primitive life forms on our planet—fossils, or to be exact, microfossils, which refers to the remains of living cells. What have survived are mainly only cell walls, which can be isolated from sedimentary rocks when the silicate-, sulphide- or carbonate-rich minerals are chemically dissolved away. The microfossils are found in the remaining carbon-containing residue, transparently thin platelets of which are prepared for microscopic studies. 

Fig. 10.1 Cellular, petrified, filamentous microfossils (cyanobacteria) from the Bitter Springs geological formation in central Australia they are about 850 million years old. With kind permission of J. W. Schopf...

The news of the oldest microfossils to be discovered was then a sensation (Schopf, 1993). They were found in western Australia in geological formations whose age had been determined some years before to be more than 3 billion years (Groves et al., 1981) interestingly, one of the formations is called North Pole . The age... 

A 13C/12C ratio about 3% above that of a standard value (the so-called VPDB standard) had been found in western Australian rock samples from the Pilbara Formation similar values were found for the Isua rock. However, since this no longer had its original morphology, the yeast-like relicts found by Pflug (1978) may not be real, and doubts have been cast, in particular by the American scientists J. W. Schopf andE. Roedder (Breuer, 1981,1982). Neither the Isua microfossils nor their 13C/12C isotope ratio could convince Bill Schopf that 3.8-billion-year-old samples were really involved. The Isua graphite flakes could also be a charred residuum from the... 

Further studies are thus required to determine whether the Earth s oldest putative microfossil assemblages from the Apex chert represent genuine primeval life forms or only a fatal delusion (Schopf et al., 2002b Brasier et al., 2002b, 2004). 

At the end of 2003, new research results led to sensational headlines Minerals Cooked Up in the Laboratory Call Ancient Microfossils Into Question was the title chosen by Richard A. Kerr for his article in Science dealing with synthetically prepared silicate carbonates. Their microstructures show morphologies which look exactly like those of filaments which had been assigned as cyanobacterial microfossils of the Precambrian Warrawoona chert formation in western Australia. The synthetic structures consist of silicate-encapsulated carbonate crystals, and in part have a helically twisted morphology reminiscent of biological objects. Simple... 

Garcia-Ruiz, J.M., Hyde Camerup, A.M., Christy, A.G., Vara Kranendonk, M.J. and Welham, N.J. (2003). Self-assembled silica-carbonate structures and detection of ancient microfossils. Science, 302, 1194-1197 and see M. Brazier (2001). Earth System Processes. Edinburgh Conference... 

Hunt, C. 2003. Metal concentrations and algal microfossil diversity in pre-industrial (pre-1880) sediment of lakes located on the Sudbury Igneous Complex in Sudbury, Ontario. Unpublished MSc. Thesis, Laurentian University, Sudbury, Ontario. 

Schopf JW (1993) Microfossils of the early Archean Apex Chert new evidence of the antiquity of life. Science 260 640-646... 

Life on Earth may have started between 3.5 and 3.9 billion years ago, as shown in Figure 3.2. The oldest microfossils were described by J. W. Schopf from the Apex Chert at Marble Bar, Western Australia (Schopf, 1992, 1993, 1998). These are dated at 3.465 Ga. Microfossils from Swaziland (South Africa) are of similar age. The North American Gunflint Chert (2 Ga) and the Belcher Group microfossils from Canada are the first occurrence of the Precambrian. ... 

For more information about the microfossils discovered and published up to 2003, see http //www. unimuenster.de/GeoPalaeontologie/Palaeo/Palbot/seitel.html... 

Do you consider possible that microfossils or at least genetic material may be found in meteorites and/or comets ... 

Fig. 1.7 Cross section of a painting (17th century, Taormina, Italy). Interestingly, the ground was prepared with a pigment obtained by crushing a biocalcarenite rock containing abundant microfossils (globigerine foraminifers, Sicily)...

Dating of speleothems from western Malaysian cave were recently reported55 in addition to those of Brazilian,56 Taiwan,43 Indian shells57 and Chinese calcitic shells with Mn2+ impurities.58 In the last one, a new intensity standard sample of CuS04. 5H20 was developed as will be described later. Past carbonate dissolution in deep sea sediments has been studied through ESR spectroscopy of microfossil foraminifera.59... 

The time period in which prebiotic synthesis of organic compounds took place is frequently misunderstood. The earth is 4.5 x 109 years old, and the earliest fossil organisms known, the Warrawoona microfossils and stromatolites, are 3.5 x 109 years old.10 The difference is 1.0 x 109 years, but the time available for life to arise was probably shorter. It probably took a few hundred million years for organisms to evolve to the level of those found in the Warrawoona formation. In addition, if the earth completely melted during its formation, then the time available would be further shortened by the time needed for the earth to cool down sufficiently for organic compounds to be stable. 

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