A note on the significance of lamination in stromatolites

The lamination found in recent stromatolites, an intrinsic feature of many of them, comprises a number of sediment-rich and organic-rich couplets. The significance of this lamination has figured in at least two avenues of research. In one is its possible influential role upon geochemical and diagenetic trends, in the other its possible calendar role. Algal growth follows a diurnal pattern but sedimentation, which is largely marine, is far less regular or predictable. The monitoring of modern algal mat surfaces has yielded much useful and accurate information concerning rates of mat accretion. Millimetre-scale lamination may be produced on a number of interacting processes but as yet no one has been able to determine with any great assurance whether it represents a daily, monthly, annual or some other regular periodic growth. The evidence from the Trucial Coast tends to show, rather, that burial, subsequent compaction, distortion and, in the case of sabkha-type sections, destruction owing to evaporite mineral growth, all tend to obliterate or at best mask any regular patterns of growth. In conclusion, one is forced to acknowledge that any computations concerning the calendar role of stromatolites are to be regarded with the utmost suspicion.