Lois Anne Nagy

Alga-like forms in onverwacht series, South Africa: Oldest recognized lifelike forms on earth

Spheroidal and cupshaped, carbonaceous alga-like bodies, as well as filamentous structures and amorphous carbonaceous matter occur in sedimentary rocks of the Onverwacht Series (Swaziland System) in South Africa. The Onverwacht sediments are older than 3.2 eons, and they are probably the oldest, littlealtered sedimentary rocks on Earth. The basal Onverwacht sediments lie approximately 10,000 meters stratigraphically below the Fig Tree sedimentary rocks, from which similar organic microstructures have been interpreted as alga-like microfossils. The Onverwacht spheroids and filaments are best preserved in black, carbonrich cherts and siliceous argillites interlayered with thick sequences of lavas. These lifelike forms and the associated carbonaceous substances are probably biological in origin. If so, the origins of unicellular life on Earth are buried in older rocks now obliterated by igneous and metamorphic events.

Transvaal Stromatolite: First Evidence for the Diversification of Cells about 2.2 x 109 Years Ago.

The well-preserved fossil remnants of filamentous blue-green algae have been found in petrographic thin sections of a dolomitic limestone stromatolite in the Transvaal Sequence of South Africa. Some of these filaments contain enlarged cells which are interpreted as akinetes. A new species and genus, Petraphera vivescenticula, is proposed for this microfossil, which is morphologically similar to the living cyanophyte genus Raphidiopsis. This would constitute the first known occurrence of cell diversification in the Precambrian with an age of about 2.2 x 109 years.

Ellipsoidal Microstructures of Narrow Size Range in the Oldest Known Sediments on Earth

Abstract The sedimentary rocks within the Onverwacht Group, which show little or no metamorphic overprint, are the oldest known sediments on earth. Some of these sediments have been dated at ∼ 3.4 × 103 years old. Microscopic examination of petrographic thin sections of these sediments has revealed round or ellipsoidal shaped microstructures of 2μ to 6μ size range. These microstructures show what appear to be double walls and are found individually or in chains or clusters. They are resistant to hot 6N HC1, hot 48 percent HF, ozone and organic solvents. These forms could be organic particulate matter of no chemical or biological evolutionary significance, or they could be the precursors to the first living cell. Finally, they could be the oldest known microfossils on earth. Until ultramicro-chemical analyses are available on these particles, great caution is needed in the interpretation of their origin.

Indications of a biological and biochemical evolutionary trend during the archean and early proterozoic

Abstract Micropaleontological observations and organic geochemical analyses imply, but certainly do not prove, that life may not have been present ∼3,800 Ma ago in Southwestern Greenland; however, physiologically complex prokaryotes flourished by the Early Proterozoic in other locations. It is, of course, also possible that life may have appeared earlier in locations other than Greenland. Investigations of Precambrian biological and biochemical evolutionary trends require interdisciplinary efforts, up-to-date instrumentation and methodology (such as ultramicrochemical analyses of individual microfossils/microstructures), and caution in the interpretation of experimental results.

Investigations of the Early Precambrian Onverwacht Sedimentary Rocks in South Africa

The Onverwacht Series is the oldest member of the Swaziland System, and it is well exposed in the Barberton-Badplaas region of the Eastern Transvaal in South Africa. The Swaziland System is a well preserved, oceanic to island arc and continental borderland sequence of volcanic and sedimentary rocks. The Onverwacht consist mainly of volcanic rocks with quite subordinate layers of tuffs, cherts and clastic sediements. These sediments appear to be the oldest known exposed sedimentary rocks on earth.

Interdisciplinary Search for Early Life Forms and for the Beginning of Life on Earth

Abstract The evolution of life and the nature of the oldest organisms depend on the atmospheric, hydropheric and lithospheric conditions during very early terrestrial history. Specialists, working in different fields of scientific endeavour, assume that the various proposed early atmospheric, hydrospheric and lithospheric models are established; this is not the case as some of the proposed models are contradictory. The results of prebiological chemical evolution simulation experiments, actual chemical analyse of very ancient rocks and ancillary micropaleontological studies also lack agreement.This article represents the first time a critical interdisciplinary inquiry has been attempted, based on astronomy geophysics, geochemistry, geology, atmospheric physics, oceanography, hydrology, chemistry and biology. Prebiological organic compounds have yet to be found in rocks. The oldest known rock (~3800 million years) of sedimentary origin, found in S.W. Greenland has not yet revealed microfossils and carbon co...