Mathematics – Logic
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21430501a&link_type=abstract
American Astronomical Society, AAS Meeting #214, #305.01; Bulletin of the American Astronomical Society, Vol. 41, p.721
Mathematics
Logic
Scientific paper
Tidal rhythmites provide sedimentary records of astronomically-forced cycles and biologically-mediated microbial activity. These ubiquitous sequences have both modern and ancient analogs. Although the bulk of past research presumes that metamorphism, Milankovitch or climatic events have annihilated or overprinted any small-scale, orbitally-influenced periodicities, recent research suggests preservation of even microlamination patterns is possible. With the present deceleration of the Earth's rotation and the recession rate of the Moon, higher tides, shorter days, and longer years (more days in a year) must have prevailed in the past. Reconstruction of recorded historical astronomical data and eclipse records support a shorter Earth day. In addition, well-preserved, Neoproterozoic rhythmites in the Reynella and Elatina Formations [1], contain tidal signatures reflecting 13.1 + 0.1 synodic months/year, 21.9 + 0.4 hours/day and a mean lunar recession rate of 2.17 + 0.3 cm/year, a little more than half the present rate. Present (3.82 cm/yr) and extrapolated lunar recession rates (2.17 cm/yr to 620 Ma) suggest that shorter, more pronounced periodicities would have existed in the Proterozoic [1]. This supporting evidence of shorter days and months with longer years helps confirm that rhythmite patterns are preserved in the Earth rock record. Modern-day geologic records contain similar cyclical laminae patterns indicative of lunar rhythms such as spring tide, neap tide, perigee and apogee.
Archean rocks contain sediment tolerant intertidal cyanobacteria relics with strong tidal signatures. These stromatolites provide early record of ancient life, reflecting both tidal sedimentation and hardy primitive tolerance to fluctuating geochemical conditions. Banded-iron formations also contain similar rhythmic sequences that are historically linked to anoxic events [2-3], however, careful reexamination of foreset-laminae thickness within ancient sedimentary successions may reveal closer ties to paleotidal cycles. [1] Williams, G.E. (2000) Review of Geophysics, 38, 37-59. [2] Cloud, P. (1968) Science, 160, 729-736. [3] Cloud, P.E. (1988) Oasis in Space.
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