Polski i globalny zapis biozdarzenia na granicy prekambr-kambr
Abstract
POLISH AND GLOBAL RECORD OF THE BIO-EVENT AT THE PRECAMBRIAN-CAMBRIAN BOUNDARY
Summary
The appearance of the morphologically complicated trace fossils in the lowermost part of the Lower Cambrian represents a bio-event marking a boundary between major stage in evolution of behaviour, which was controlled by a combination of environmental and biological factors. The diversification of behaviour of the benthos in the early Phanerozoic is recorded in the transitional Precambrian-Cambrian strata in southern Poland. The complication of morphology of trace fossils appears there at the base of the Platysolenites Zone. Here, also the first occurrence of the Early Cambrian acritarchs and small shelly fossils was noted. The isochroneity of these three entirely different bio-events points to a possibility of including into the Lower Vendian the Sabellidites Zone (up to now regarded traditionally as the Lower Cambrian). The world-wide distribution, a rapid evolution, lack of provincialism, and lack of post-mortem transport make trace fossils an ideal group to define and correlate the Precambrian-Cambrian boundary. The Fortune Head section (southeastern Newfoundland) is the first global-stratotype candidate with established ichnostratigraphy. The boundary was placed there at the base of the Phycodes pedum ichnozone. During the St. John's conference (Newfoundland 1987) the Precambrian-Cambrian Boundary Working Group decided that this ichnozone is considered the global ichnocorrelation level for the Lower Cambrian.
Summary
The appearance of the morphologically complicated trace fossils in the lowermost part of the Lower Cambrian represents a bio-event marking a boundary between major stage in evolution of behaviour, which was controlled by a combination of environmental and biological factors. The diversification of behaviour of the benthos in the early Phanerozoic is recorded in the transitional Precambrian-Cambrian strata in southern Poland. The complication of morphology of trace fossils appears there at the base of the Platysolenites Zone. Here, also the first occurrence of the Early Cambrian acritarchs and small shelly fossils was noted. The isochroneity of these three entirely different bio-events points to a possibility of including into the Lower Vendian the Sabellidites Zone (up to now regarded traditionally as the Lower Cambrian). The world-wide distribution, a rapid evolution, lack of provincialism, and lack of post-mortem transport make trace fossils an ideal group to define and correlate the Precambrian-Cambrian boundary. The Fortune Head section (southeastern Newfoundland) is the first global-stratotype candidate with established ichnostratigraphy. The boundary was placed there at the base of the Phycodes pedum ichnozone. During the St. John's conference (Newfoundland 1987) the Precambrian-Cambrian Boundary Working Group decided that this ichnozone is considered the global ichnocorrelation level for the Lower Cambrian.