Three world-wide used geologic terms derived from the area around the north German Harz Mountains: “Oolithi”  and nearly two hundred years later “Ooid” and ”Stromatolith” . These terms all describe carbonate grains and rocks of the Lower Triassic Buntsandstein Group. The widespread Buntsandstein Group of cebtral Europe consists of red and variegated sandstones and mudstones which stretch from Lorraine in France to the Holy Cross Mountains in eastern Poland. It is a typical dominated by red beds deposited in a large inland basin, the Central European Basin. Braided and meandering rivers brought siliceous grains and mud from the hinterland towards the centre of the basin. At times the inflow of water led to large but shallow lakes at the centre of the basin. When the rainy seasons vanished, the water of the lake evaporated. Microbial calcite-producing communities flourished in the absence of higher organisms. Calcite ooids formed in the shallow environment under the impact of wind and wave action bars or shoals which are now preserved at the margin of the basin and palaeohighs from the Netherlands to Poland. Eventually the lakes vanished and small ephemeral rivers reached the centre and brought only mud with them.
The sediments of the Lower Buntsandstein, are nearly devoid of fossils, body fossils as well as trace fossils. The reason of this scarceness may be not abnormal salinity, but rapidly changing environmental conditions as the shallow playa lake has no buffer capacity against fluctuations of various environmental parameters. The etched surfaces of stromatolites are because of the decay of organic matter under a cover of clay or living mat led to formation of CO2, lowering the pH and consequently to acidification of the water and dissolution of carbonate.
Some prerequisites of stromatolitic growth can be deduced from observations in the field. Muddy water or mud layers excluded stromatolites or terminated their growth. The microbial community did not survive a mud cover or muddy water. This effect may be the reason for their restriction to the Eichsfeld Palaeohigh. Here, the sandy and muddy sediments were diverted west and east of the high on their way towards the basin. The more extended areas of oolites indicate that the ooid producing microbes are not so sensitive. The position of stromatolites at top of oolite beds seems to reflect a directional evolution, most likely of the water chemistry, e.g. alkalinity or supersaturation in respect of calcium carbonate.
The observed photoautotrophy points to cyanobacteria, at least as a component of the microbial community. There is a high potential of preservation by the absence of grazers and browsers and an early lithification, although the latter cannot be proved.
There was a long-lasting discussion in the scientific community about the formation of ooids. During the 19th and 20th century most scientists thought of inorganic origin, a precipitation due to supersaturation in regard of calcium and carbonate. Calcite or aragonite may precipitate around a nucleus of a quartz or carbonate grain. Only Kalkowsky (1908) thought of an organic origin produced by colonies of lime secreting phyto-organisms. During the last twenty years an increasing number of indications arewere found that organic biofilms are involved in the formation of ooids.
To summarize, Kalkowsky (1908) stated that
p. 100 § 64 Regarding the environment of the oolites in the north German Bunter Sandstone, it is generally assumed that they have formed in a shore facies.
One could easily be tempted to think already now of salt lakes as area of their formation.
p. 118 § 88 Stromatolites were always associated with oolites.
p. 123 § 94 Ooids resemble growing bacterial colonies as observed in a Petri dish. Ooids are therefore probably produced by colonies of lime secreting phyto-organisms.
p.124 § 96 We have to assume that simple plants gave rise to limestone precipitation.
My aim has been to show that the oolites and stromatolites of the north German Bunter Sandstone are inherently of organic origin.
Fifty years after Kalkowsky published the classic paper Richard Chase recognized the first convincing modern analogues of “stromatoliths” around the shores of Hamelin Pool, Western Australia . Recent investigations of both localities reveal a number of interesting parallels between the environment of Hamelin Pool and that of the Basin in which the association described by Kalkowsky. In both cases stromatolites grow on stable or firm ground in turbulent environments characterized by low sedimentation rates, little fine grained sediment, virtually no terrigenous input, rapid cementation and abnormal or fluctuating salinity.
Kalkowsky’s stromatolites occur on the surface of oolite beds. Laminated crusts (called stromatoid by Kalkowsky and interpreted as being formed by syndepositional cementation) also occur in these rocks. Both stromatolites and laminated crusts are concentrated in specific layers traceable throughout quarry faces. In places the stromatolites are clearly syndepositional with rippled ooid sand. Spongy-fenestrate and fan-like stromatolitic microstructures can be distinguished, and both have undergone intense sparitization. The upper surfaces of some stromatolites are pitted due to syndepositional dissolution. The stromatolites may incorporate variable amounts of ooids, quartz grains and other material.
Hamelin Pool stromatolites also occur associated with ooid sands [3,8]. Subtidal stromatolites grow on rock substrate or crusts formed by penecontemporaneous cementation of marine sands, and are surrounded by mobile oolitic rippled sands and sand waves. The subtidal stromatolites have a laminoid fenestral fabric consisting of ooid and other carbonate sand grains cemented by micritic cements . Micritisation of sand grains begins soon after deposition and gradually destroys the original structure of the incorporated ooids and other grains [9,10]. Stromatolites in the intertidal zone are thought to be subtidal forms stranded by sea-level fall and modified by intertidal microbial communities . While the Buntsandstein stromatolites originated in a hyposaline and alkaline lake environment during the high stand of water level, and the Hamelin Pool stromatolites a forming in a hypersaline marine embayment during a period of regression, there are many environmental similarities. In both cases conditions favourable for ooid formation precedes the initiation of stromatolite growth, but the stromatolites co-exist with ooid sands, and incorporate ooid grains into their structures. The morphology of the many of the subtidal Shark Bay stromatolites is clearly influenced by the erosive effects of ooid sand waves migrating around them. Once formed, early diagenesis progressively obliterates the structure of ooid grains incorporated into the stromatolites. The association of stromatolites and ooid sands is of considerable geological significance. In another present-day environment the stromatolites of Lee Stocking Island in the Bahamas show a similar association with migrating ooid sand waves to that found in Hamelin Pool . The association of stromatolites and oolites dates back to the Archean. One of the oldest occurrences of the association is known from the 2, 72 Ga. Tumbiana Fm., Fortescue Gr. Pilbara Block in Western Australia.
Even the first stromatolites known to science are associated with oolitic limestones, for, 25 years before Kalkowsky’s work was published, James Hall had formally named Cryptozoon proliferum, from the oolitic Cambrian Hoyt Formation of Saratoga Springs, New York State .
 Brueckmann F.E. (1721).- Specimen physicum exhibens historiam naturalem, oolithi seu ovariorum piscium & concharum in Saxa.- Mutatorum, Helmestadii, Salomoni & Schnorrii, 21 pp.
 Kalkowsky E. (1908): Oolith und Stromatolith im norddeutschen Buntsandstein. – Zeitschrift der deutschen geologischen Gesellschaft, 60, p. 68–125.
 Logan B.W., Hoffman P. & Gebelein C.D., (1974): Algal Mats, Cryptalgal Fabrics, and Structures, Hamelin Pool, Western Australia. – In: Logan B.W., Read J.F., Hagan G.M., Hoffman P., Brown R.G., Woods P.J. & Gebelein C.D., (eds.): Evolution and Diagenesis of Quaternary Carbonate Sequences, Shark Bay, Western Australia. American Association of Petroleum Geologists, Tulsa, Oklahoma, Memoir 22, p. 140 – 194.
 Brehm U., Palinska K.A. & Krumbein W.E. (2004).- Laboratory cultures of calcifying biomicrospheres generate ooids - A contribution to the origin of oolites.- Carnets de Géologie Notebooks on Geology, Maintenon, Letter 2004/03 (CG2004_L03), 6 pp.
De Vries Klein G. (1965): Dynamic Significance of Primary Structures in the Middle Jurassic Great Oolite Series, Southern England. In Middleton G.V., (ed.): Primary Sedimentary Structures and their Hydrodynamic Interpretation. SEPM Special Publication 12, p. 173-192.
 Chase Richard, Personal Communication to RVB 1/8/2007
 Paul J. & Peryt T. M. (2000): Kalkowsky's Stromatolites Revisited (Lower Triassic Buntsandstein, Harz Mountains, Germany). - Palaeogeography, Palaeoclimatology, Palaeoecology 161, p. 435-458
 Davies G.R. (1970): Carbonate Bank Sedimentation, Eastern Shark Bay, Western Australia. – In: Logan B.W., Davies G.R., Read J.F. & Cebulski D.E. (eds.): Carbonate Sedimentation and Environments, Shark Bay, Western Australia. - The American Association of Petroleum Geologists, Tulsa, Oklahoma, Memoir 13, p. 85-168.
 Monty C.L.V. (1976): The Origin and Development of Cryptalgal Fabrics. – In: Walter M.R. (ed): Stromatolites. Elsevier Amsterdam, Developments in Sedimentology 20, p. 193-249.
 Reid R.P., James N.P., Macintyre I.G., Dupraz C.P. & Burne R.V. (2003): Shark Bay Stromatolites: Microfabrics and Reinterpretation of origins. - Facies 49, p. 45–53.
| Burne R.V. (1991-92): Lilliput’s Castles: Stromatolites of Hamelin Pool. Landscope 7. p. 34-40.
 Dill R.F. (1991): Subtidal Stromatolites, Ooids and Lime Encrusted Muds at the Great Bahama Bank Margin. Contributions in Marine Geology in Honour of Farncis Parker Shephard. In: Osborne R.H. (ed.): From Shoreline to Abyss. - SEPM Special Publication 46, p. 147–171. Hall J. (1883): Plate VI and explanation: Cryptozoon , N. G., Cryptozoon proliferum n. sp. - In: PIERSON, H.R. (ed.): Thirtysixth annual report of the trustees of the State Museum of Natural History to the legislature. - N. Y. Senate paper 1883/53, Albany.