Trace fossils and biofabrics at the Precambrian–Cambrian boundary interval in western Mongolia

Abstract

A small suite of trace fossils from the Zavkhan Basin (Govi-Altay) includes many of the ichnotaxa typical of the Nemakit-Daldynian, Tommotian and younger Cambrian stages, and other indeterminate forms. The traces are almost entirely from the sandstone intervals of the large-scale alternations of carbonate and siliciclastic sediments, thus emphasizing the facies and taphonomic controls on trace fossil distribution, and hence the inherent difficulties in using trace fossils in detailed global correlation, especially in using first appearances. The assemblage of traces and biofabrics is seen as resulting from the partly non-uniformitarian (non-actualistic) sedimentary environments that pertained over the boundary interval, rather than as evolutionary failures and subsequently vacated environments.

Integrated chemo- and biostratigraphic calibration of early animal evolution: Neoproterozoic–early Cambrian of southwest Mongolia

“…A revised zonal scheme is shown at right, alongside that put forward by Voronin et al (1982). The first appearance of two main trace fossil assemblages is shown against the log (after Goldring & Jensen, 1996, this issue). The Precambrian-Cambrian boundary is provisionally placed at the lowest level with a Cambrian-type trace fossil asemblage.…”

“…The upper part of the section ('GK' units 17-21) was studied in the 'southern block', alongside researches on sequence stratigraphy and trace fossils (Lindsay et al 1996a, this issue;Goldring & Jensen, 1996, this issue). The carbon isotope profiles (Figs 8,9) show a number of distinct features.…”

Concerning the Original Viewpoint of Biogeologic Accumulation of the Old Bedded Phosphorites in the Khubsugul and Zavkhan Basins of Mongolia

“…in bedded phosphorites of the Khesen and Tsagaanolom formations [2] [17]. The phosphate-aluminous-bearing Bayangol formation has abundant assemblages of trace fossils which are confirmed by R. Goldring and S. Jensen [26]. It should be emphasized that we have discovered a stony or black metaphosphorite occurrence with high content of Al 2 O 3 (up to 15% -33%) in the Bayangol formation close to the Alagiin Davaa deposit (Khundlun Uul area) of the Zavkhan phosphate basin [16].…”

Cambrian Trace Fossil Zoophycos from the Czech Republic

“…De (1993) reported Zoophycos from the Lower Cambrian strata of Kashmir, India. Goldring & Jensen (1996) noted Zoophycos from Cambrian Stage 2(?) in western Mongolia.…”