Место издания: Florence , Год издания: 2004

Bacteriomorphic forms are wide distributed in Cretaceous phosphories. We have found them in all phosphorites studied by us of this age: in the Lower Cretaceous Egorievsk and Upper Cretaceous Polpino phosphorite deposits of the East-European Platform, Upper Cretaceous phosphorites of the Siberian Platform and Pesca Boyaca region of Columbia and the Upper Cretaceous-Lower Paleocene Bengerir phosphorite deposit of Morocco, Upper Jurassic-Lower Cretaceous phosphorites of the West Siberian Basin. The most distributed biomorphic structures in studied phosphorites are cocco-like and tubular, sometimes rod-like. Several appearances of the cocco-like forms in the Egorievsk and Polpino phosphorites can be distinguished. In one case they represent isolated round structures ranging from 1 to 3,5 mm in size. These forms were encountered in cavities of shells of lager organisms. In other cases cocco-like structures are combined into accumulations of many of the individual forms. Some cocco-like forms are connected to subsrate by thin filamentous shoots (so-called pilas). In phosphorite from Morocco the chains composed of cocco-like forms were revealed. The length of these chains reaches 40 mm., the individual forms range from 1 to 5 mm in size. We distinguish these chains as streptococco-like formations. In individual cases the structure of the mineralized bacteria is seen: an external shell (capsule or cell wall) and inner area consisting of protoplasm separated from the shell by a hollow ring-shaped gap. Sometimes their inner area is not mineralized. In phosphorites of Columbia the cocco-like structures constitute in one case thin layers of ooids, in other cases the walls of tubes (capsules). The ooids are 250-300 mm in size and can be distinguished as microoncolites. The thickness of their spherical layers is 5-7 mm. The cocco-like forms which compose these layers range from 0,5 to 1 mm in size. The tubes (capsules, filaments) represent another bacteriomorphic structures often observed in phosphorites of different ages. In Cretaceous phosphorites of Columbia they represented capsules (tubules) identified as shells of the cyanobacterial filaments. The visible length of these capsules reaches 20 mm, and diameter ranges from 6 to 12 mm. The diameter of the inner canal of the capsules ranges mainly from 0,5 to 1-2 mm, sometimes 5-8 mm. Rod (bacillus)-like structures were met in Egorievsk phosphorites. The similar forms are known in Chile-Peru shelf phosphorites.