- Steve.
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Dear Steve:
I provide the following based upon your E-mail to me dated October 11, 1998. Please feel free to disseminate this as you see fit. I am not interested in subscribing or sending this directly to the evolution listserver, because that listserver appears to contain a mostly philosophic rather than a scientific debate. You can serve as my spokesman, but don't take any of my comments out of context. Either forward the entire message, or none of it.
I've always been intrigued by the ways that geological information can be misinterpreted. In addition, I've commonly wondered how a creationalist might be able to misinterpret tidal rhythmites, i.e., if our rhythmites indicate sedimentation rates of centimeters/month or meters/year, then perhaps one could misinterpret the entire sedimentary rock record as having formed within only a few thousand years. But then that would really be taking things out of context, wouldn't it?
Art Chadwick's mention of our 10-year-old paper (Geology, April 1989) is intriguing in his apparent misinterpretations. There has been much more work done of these facies since that time and I've summarized some of that work in the following paragraphs.
The following information converns the geological and sedimentological aspects of tidal rhythmites, which are a subset of cyclic rhythmites as reviewed recently by Archer (1998, references given below; abstracts for these papers are available at http://www-personal.ksu.edu/~aarcher) and reprints can be requested by Email sent to aarcher@ksu.edu). Tidal rhythmites are a common Carboniferous-age facies that occurs directly overlying coals (Archer and Kvale, 1993). Some of the best examples occur in laminated siltstones in Indiana (Kvale et al, 1989; Kvale and Archer, 1991) and Kansas (Lanier et al., 1993; Archer et al., 1994a, b). A number of other examples have also been reported, including Carboniferous occurrences in Kentucky (Greb and Archer, 1995). Similar rhythmites occur in Precambrian-age rocks (900 mybp) as reported by Chan et al. (1994).
According to your e-mail, Art Chadwick has acquired a sample from the Mansfield Formation of Indiana that contains a neuropterid-type fern that was upright and cut across laminations. Chadwick appears to think that this is a significant discovery, however, it is hardly an unusual find. I have seen many examples of neuropterids that cut across laminations from tidally laminated siltstones from various localities in Indiana and Kansas discussed above. Neuropterids are hardly "very delicate lace-like leaves" as suggested by Chadwick. They were thick, very resistant leaves and that is why they are among the most common occurrences of Carboniferous-age fossil plants.
The upright neuropterids are interesting, but there are many types of upright plant materials within tidal rhythmites. All these materials cut across laminations. Most of the upright plants appear to come from rhythmites near the level of the underlying coal. Upright trunks of tree-size plants are also common. In Indiana, these consist mostly of lycopods (club moss) and in Kansas are more commonly calamites (horsetails). All this upright plant material has been noted many times in our publications and used to infer localized, high rates of sedimentation.
The cyclicity observed in the lamina-thickness series from these rhythmites provides evidence for their origin by tidal processes (Archer, 1995, Archer et al. 1995; Kvale et al, 1995). Rocks containing tidal periodicities have been reported from rocks of many different ages (see review in Archer, 1996a). Computer-based modeling, using tidal periodicities, can reproduce the various types of periodicities observed within rhythmites (Archer, 1994; Archer and Johnson, 1997). Because there was a single global paleocean during the Carboniferous, tidal processes were apparently especially prevalent during that period of earth history (Archer, 1996b).
The tidal rhythmite hypothesis that we have advocated is strongly supported by modern analogs. We have been working for several years in the upper reaches of the Bay of Fundy, Nova Scotia, Canada. Fluvio-tidal bars in that area are depositing laminations that are very similar to those observed in the Carboniferous rhythmites of Indiana and Kansas. Archer and Johnson (1997) have described the mechanics of the deposition whereby 1 cm of silt can be deposited during each tidal cycle (twice daily). Art Chadwick suggested that upright fronds could not survive in a setting where "daily tidal current swept repeatedly across them." However, in the modern analog settings, the currents do not "sweep" but are extremely low-energy flooding of the bar tops with waters that are saturated with silt-sized sediment. Conversely, the tidal current are stong and do "sweep" the channels between the bars, but only low-energy currents occur on the tops of the bars where the rhythmites are deposited.
Because of this low-energy sedimentation, very finely detailed structures are preserved on the lamina surfaces. These include raindrop imprints, foam marks, insect-walking tracks, bird footprints, and a host of other unusual features. Similar rain drop imprints, foam marks and insect-walking tracks are found in the Carboniferous rhythmites of Kansas (see Lanier et al., 1993). Obviously, we don't find any bird tracks in the Carboniferous rhythmites, but amphibian tracks are common. Another modern analog with many similarities occurs in the Bay of Mont Saint Michel in France (Tessier et al., 1995). These features all clearly indicate an intertidal setting.
Working with these rhythmites has greatly increased my understanding of how important it is to have good modern analogs. I've become more and more convinced that any sedimentological model that doesn't have a modern analog isn't worth much. Without the excellent modern analogs of tidal rhythmites in Canada and France, it would be much more difficult to provide convincing evidence of a tidal origin of the Carboniferous rhythmites. Nonetheless, if anyone out there can incorporate all the above evidence into some type of reasonable, alternative model, I'd be happy to evaluate it.
References (cited and additional, in reverse chronological order: reprints or xeroxes available upon request to aarcher@ksu.edu ).
Archer, Allen W., 1998. Implications of Carboniferous cyclic rhythmites. Geotimes, v. 5, p. 23-26.
Archer, Allen W., and Troy W. Johnson, 1997. Modeling of cyclical rhythmites (Carboniferous of Indiana and Kansas, Precambrian of Utah, U.S.A.) as a basis for reconstruction of intertidal positioning and paleotidal regimes. Sedimentology, v. 66, p. 991-1010.
Archer, Allen W., 1996a. Reliability of lunar orbital periods extracted from ancient cyclic tidal rhythmites: Earth and Planetary Science Letters, v. 141, p. 1-10.
Archer, Allen W., 1996b. Panthalassa: paleotidal resonance and a global
paleocean seiche: Paleoceanography, v. 11, p. 625-632.
Archer, Allen W., 1995. Modeling of tidal rhythmites based on a range of diurnal to semidiurnal tidal-station data: Marine Geology 122: 1-10.
Archer, Allen W., Gerald Kuecher, and Erik P. Kvale, 1995. The role of tidal-velocity asymmetries in the deposition of silty tidal rhythmites (Carboniferous, Eastern Interior Coal Basin): Journal of Sedimentary Research, A65: 408-416.
Feldman, Howard R., Gibling, Martin R., Archer, Allen W., Wightman, Winton G., and Lanier, William, P., 1995. Stratigraphic architecture of the Tonganoxie Paleovalley Fill (Lower Virgilian) in Northeastern Kansas. American Association of Petroleum Geologists Bulletin, 79, p. 1019-1043.
Greb, Stephen F., and Allen W. Archer, 1995. Rhythmic sedimentation in a mixed tide and wave deposit, Hazel Patch Sandstone (Pennsylvanian), Eastern Kentucky Coal Field: Journal of Sedimentary Research, part B, v. 65, p. 93-106.
Kvale, Erik P., Jeff Cutright, Douglas Bilodeau, Allen W. Archer, Hollis R. Johnson, and Brian Pickett, 1995, Analysis of modern tides and implications for ancient tidalites: Continental Shelf Research, v. 15, p. 1921-1943.
Tessier, Bernadette, Allen W. Archer, William P. Lanier, and Howard R. Feldman, 1995, Comparison of ancient tidal rhythmites (Carboniferous of Kansas and Indiana, USA) with modern analogues (the Bay of Mont-Saint-Michel, France): Special Publications of the International Association of Sedimentologists, v. 24, p. 259-271.
Archer, Allen W., 1994. Extraction of sedimentological information via computer-based image analyses of gray shales in Carboniferous coal-bearing sections of Indiana and Kansas, USA: Mathematical Geology, v. 26, p. 47-65.
Archer, Allen W., Howard R. Feldman, Erik P. Kvale, and William P. Lanier, 1994a. Pennsylvanian (Upper Carboniferous) fluvio- to tidal-estuarine coal-bearing systems: delineation of facies transitions based upon physical and biogenic sedimentary structures. Palaeogeography, Palaeoclimatology, Palaeoecology, v. 106, p. 171-185.
Archer, Allen W., William P. Lanier, Howard R. Feldman, 1994b. Fluvio-estuarine transitions within incised paleovalley fills, Douglas Group (Stephanian; Upper Carboniferous) of Kansas, U.S.A: in R. Boyd, R. Dalrymple, and B. Zaitlin, eds., Incised Valley Fill Systems, SEPM Special Paper 51, p. 175-190.
Chan, Marjorie A., Erik P. Kvale, Allen W. Archer, and Charles P. Sonett, 1994. Oldest direct evidence of lunar-solar tidal forcing encoded in sedimentary rhythmites, Proterozoic Big Cottonwood Formation, central Utah: Geology, v. 22, p. 791-794.
Kvale, Erik P., Gordon S. Fraser, Allen W. Archer, Ann Zawistoski, Nathan Kemp, and Patrick McGough, 1994. Evidence of seasonal precipatation in Pennsylvanian sediments of the Illinois Basin: Geology, v. 22, p. 331-334.
Archer, Allen W., and Erik P. Kvale, 1993. Origin of gray-shale lithofacies ("clastic wedges") in U.S. midcontinental coal measures (Pennsylvanian): an alternative explanation, in J. C. Cobb, and B. Cecil, eds., Modern and Ancient Coal-Forming Environments: Geological Society of America, Special Paper 286, p. 181-192.
Lanier, William P., Howard R. Feldman, and Allen W. Archer, 1993. Tidally modulated sedimentation in a fluvial to estuarine transition, Douglas Group, Missourian-Virgilian, Kansas: Journal of Sedimentary Petrology, 63:860-873.
Archer, Allen W., Erik P. Kvale, and Hollis R. Johnson, 1991. Analysis of modern equatorial tidal periodicities as a test of information encoded in tidal rhythmites, in D. G. Smith, G. E. Reinson, B. A. Zaitlain, and R. A. Rahmani, eds., Clastic Tidal Sedimentology: Canadian Society of Petroleum Geologists, Memoir 16:189-196.
Kvale, Erik P., and Allen W. Archer, 1991. Characteristics of two Pennsylvanian-age semidiurnal tidal deposits in the Illinois Basin, U.S.A, in D. G. Smith, G. E. Reinson, B. A. Zaitlain, and R. A. Rahmani, eds., Clastic Tidal Sedimentology: Canadian Society of Petroleum Geologists, Memoir 16:179-188.
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-- Steven H. Schimmrich, Assistant Professor of Geology Department of Geology, Geography, and Environmental Studies Calvin College, 3201 Burton Street SE, Grand Rapids, Michigan 49546 sschimmr@calvin.edu (office), schimmri@earthlink.net (home) 616-957-7053 (voice mail), 616-957-6501 (fax) http://home.earthlink.net/~schimmrich/