Tamadjert

Misrepresentations of the Lower and Upper Boundaries of the Ordovician Glacial Tamadjert Formation in Oard (1997) and Oard (2009a)

Kevin R. Henke, Ph.D.

Updated August 26, 2021

Glaciogenic Origin of the Tamadjert Formation of North Africa

For many years, glacial features have been recognized in the Ordovician Tamadjert Formation (Unit IV) of north Africa (e.g., Biju-Duval et al. 1981; Le Heron 2010; Deschamps et al. 2013; Zazoun and Mahdjoub 2011; and their references). Today, the evidence for Ordovician glaciations in north Africa remains stronger than ever contrary to the hopes of young-Earth creationist (YEC) Oard (2009a, p. 119).

As part of his unrealistic efforts to transform all Ordovician glacial deposits into products of Noah’s Flood, Oard (1997, pp. 78-80) tries to portray the upper and lower boundaries (contacts) of the Tamadjert Formation (also Unit IV) as being “flat” and that these supposedly flat boundaries are more consistent with Flood geology than glaciogenic origins.

Lower Boundary of the Tamadjert Formation

The pre-glacial In Tahouite Formation (Unit III-3) usually lies below the Tamadjert Formation (Zazoun and Mahdjoub 2011). As mentioned in Oard (2009a, pp. 117-118), Oard (1997, pp. 78-79) used the following seven references to argue that the lower boundary of the Tamadjert Formation was “flat”, which supposedly supports an aqueous (Flood) rather than a glaciogenic origin:

· Biju-Duval et al. (1981, p. 101);

· Deynoux and Trompette (1981, pp. 92, 95);

· Deynoux (1985, p. 98);

· Schermerhorn (1970, p. 8);

· Allen (1975, p. 275);

· Bennacef et al. (1971, p. 2230, 2235); and

· Fairbridge (1979, p. 137).

To his credit, Oard (2009a, pp. 117-118) now admits that he made a mistake in citing Biju-Duval et al. (1981, p. 101), which refers to the upper boundary of the Tamadjert Formation rather than the lower one (also see below). But what about the other six references? Did Oard (1997, pp. 78-79) properly cite these references? The answer is no! Allen (1975, p. 279) describes the gentle dipping slopes of the Pre-Silurian Paleozoic rocks overlying the Precambrian rocks in the Sahara basin of north Africa. After raising questions about the glacial interpretation of the north African rocks, Schermerhorn (1970, p. 8) briefly discusses the paleoslopes in the rocks that existed before, during, and after the Ordovician glaciation. However, these statements from Allen (1975, p. 279) and Schermerhorn (1970, p. 8) never say anything about the lower boundary of the Tamadjert Formation being “flat.” To the contrary, Allen (1975, p. 279) describes the contact underlying glacial Unit IV (the Tamadjert Formation) as having deep relief:

“Unit IV lies disconformably on a deeply valleyed surface cut into the underlying strata.”

As for the other four references, Oard (1997, pp. 78-79) totally misquoted them as well, as I explain in my 1999 essay. Here is the relevant section of my essay:

“U-shaped valleys and other glacially eroded features are expected to be found underneath glacial deposits. Oard ([1997], p. 78-79) misuses the literature and tries to portray the contact between the glacial deposits of the Ordovician Tamadjert Formation and their underlying non-glacial rocks as ‘flat’ and devoid of evidence of glacial erosion. As examples, Oard ([1997], p. 78) misquotes three references (Biju-Duval et al., 1981, p. 101; Deynoux and Trompette, 1981, p. 92, 95; Deynoux, 1985, p. 98) and claims that these references indicate that the glacial rocks lie on an ‘exceptionally flat surface’ over the Sahara. In reality, they all state that on a large or regional scale, the contact APPEARS flat, but locally the contact is uneven with up to several hundred meters of relief. Specifically, Deynoux (1985, p. 98) states:

‘The glacial deposits overlie a surface which is very planar on a large scale but uneven on a local scale.’

Deynoux and Trompette (1981, p. 92) says:

‘The lower boundary of the glacial formations is roughly planar on the scale of the basin but uneven on a local scale with numerous down-cutting paleovalleys and paleodepressions which are relatively deep, with amplitudes up to 200 m.’

Oard ([1997], p. 78-79) also misquotes Fairbridge (1979, pp. 134, 137) to give the false impression that the lower contact of the glacial Tamadjert Formation is ‘almost dead-flat.’ However, Fairbridge (1979, p. 134) refers to the contact between Precambrian rocks and overlying Orodovician sandstones, and not the Tamadjert Formation, as being "almost flat-lying." In this case, Oard's (1997, pp. 78-79) reference to Fairbridge (1979) does not even apply to the Tamadjert Formation.

In a similar situation, Oard ([1997], p. 78) also misquotes Bennacef et al. (1971, p. 2230, 2235) and again claims that the contact underlying the Ordovician glacial rocks is ‘perfectly flat.’ In reality, Bennacef et al. (1971, p. 2230) are describing the contact between largely Precambrian igneous and metamorphic ‘bedrocks’ (Oard’s Figure 10.3, p. 79) and the overlying NON-GLACIAL Ajjers Formation (‘Unit II’ in Oard’s Figure 10.3, p. 79 classification). In most places, the Tamadjert Formation (‘Unit IV’) overlies the sedimentary rocks of the In Tahouite (‘Unit III’) and Ajjers formations rather than the lower most Precambrian igneous and metamorphic rocks (Bennacef et al., 1971).

Discussions on the glacial Tamadjert Formation are also in Bennacef et al. (1971, p. 2235). Like the other references, Bennacef et al. (1971, p. 2235) gives descriptions of contacts that are far from flat. In the Tassili N’Ajjer region, in particular, the contact underlying the Tamadjert Formation consists of 100-300 meter deep paleovalleys, which once contained the glaciers that deposited the Tamadjert Formation. Frakes (1979, p. 120) also describes the unconformity below the Tamadjert Formation as being irregular and having subglacial valleys up to 40 km long and 300 m deep. In places, In Tahouite Formation sandstones have been sheared off, pushed forward in slices, and carried down paleovalley slopes (Bennacef et al., 1971, p. 2235). The authors interpret the features as resulting from ice thrusting. Some of the Ordovician glaciers of North Africa were described as flowing through precarved valleys. Some of these valleys have characteristic U-shaped glacial profiles (Bennacef et al., 1971, p. 2235), which were carved by ice and water (Fairbridge, 1979, p. 139). Again, these descriptions are hardly consistent with Oard’s claims of flat and undisturbed formations under the Ordovician glacial deposits.” [Capitalization from 1999]

So, not one of the seven references in Oard (1997, pp. 78-79) supports his argument about the lower boundary of the Tamadjert Formation being so flat that it could not have formed because of glaciers! This is clearly a case of sloppy literature abuse, where Oard (2009a, pp. 117-118) boasts about mentioning seven references in Oard (1997, pp. 78-79) when in reality he has zero accuracy.

In a more recent reference, Zazoun and Mahdjoub (2011, p. 65) further describes the Late Ordovician glacial paleovalleys of the northern Tassilis, Algeria, as having depths of 100-300 meters. Zazoun and Mahdjoub (2011, pp. 67-68) also mention that the lower boundary of the Ordovician glacial deposits occurs over large parts of north Africa and even in Saudi Arabia:

“The base of the Tamadjert Formation is a major erosional surface associated with N-S valleys with a width varying between 1 and 3 km. Such incisions have been identified all over the northern margin of Gondwana in Algeria, Libya, Morocco, Mauritania, Benin-Niger and Saudi-Arabia.” [references and references to figures removed]

Oard (1997, p. 83) Undermines his Previous Arguments on pages 78-79

Rather than attempting to defend the claims in Oard (1997, pp. 78-79) that the local relief on the lower boundary of the Tamadjert Formation is inconsistent with a glacial origin, Oard (2009a, p. 118) makes a point of reminding me that Oard (1997, p. 83) finally admits that the lower boundary of the Tamadjert Formation is only “dead flat” on a large scale. Oard (1997, p. 83) states:

“Although the lower boundary of the Tamadjert Formation is ‘dead flat’ on a large scale, these U-shaped valleys are small-scale paleovalleys incised in the surface by a northward moving medium.”

Of course, any land surface will appear flat on a large-enough regional scale. However, why does Oard (1997, pp. 78-79) misquote seven references and hide the relevant issue of scale from his readers until a brief statement in an entirely different section of the chapter several pages later on p. 83? Why wasn’t Oard (1997) simply upfront with this admission of only large-scale flatness and put it where it belongs on pp. 78-79? More importantly, since Oard (1997, p. 83) and Oard (2009a, p. 118) admit that the flatness is only on a large scale, perhaps Mr. Oard could explain how his anti-glacial arguments based on “flatness” in Oard (1997, pp. 78-79) are even relevant. That is, how are several hundred meters of local relief on the lower Tamadjert boundary and only larger scale flatness any problem at all for a glaciogenic origin? How is the local relief on the lower Tamadjert boundary any different than the large scale “flat surfaces” of the Canadian Shield of western Ontario, which were glacially eroded during the Pleistocene? As I stated in my 1999 essay, Oard (1997, pp. 78-79 and also Table 10.1, p. 80) tries to portray the Ordovician Tamadjert Formation as not being typical of Pleistocene or modern glacial sediments. However, researchers, such as Bennacef et al. (1971, p. 2235), long ago concluded otherwise:

“The distribution of topographic landforms [in the Ordovician glacial deposits] is similar to the landscapes of Quaternary continental ice sheets.”

To give some perspective on the Bennacef et al. (1971) quotation, a reader of this essay found the following quotation from Krabbendam and Bradwell (2014), which describes the typical relief on hard Precambrian rocks resulting from Pleistocene glaciations in eastern Canada, Finland, Sweden, western Greenland and northwestern Scotland:

"In the Northern hemisphere, Pleistocene ice sheets covered large flat-lying shield areas, now typically characterised by an exposed bedrock landscape of numerous knolls or ridges and a multitude of lake-filled basins. Although the large-scale relief of this landscape is limited, such landscapes commonly show a rugged undulating hilly relief, narrow linear valleys and an abundance of closed rock basins. Roughness wavelength typically ranges from 10 – 1000 m and amplitudes up to 100 m."

Mr. Oard finally needs to look at all of the 21^st century evidence from the Ordovician deposits of north Africa and recognize that his Flood geology scenario can’t explain most of it and is a failure.

Upper Boundary between the Tamadjert Formation and Overlying Deposits

Post-glacial Silurian marine shales commonly occur above the glacial Tamadjert Formation (Le Heron 2010). In some locations, the Tamadjert Formation is overlain by a thin sandstone (Bennacef et al. 1971, p. 2241; Le Heron 2010). The upper boundary of the Tamadjert and the overlying shales and sandstone resulted from a post-glacial rise in sea level from the melting Ordovician glaciers; that is, erosion and sediment deposition from a post-glacial marine transgression (Lüning et al. 2000; Zazoun and Mahdjoub 2011). Oard (1997, p. 79) quotes Biju-Duval et al. (1981, p. 101) and describes the boundary between the Tamadjert Formation and the overlying Silurian rocks as “perfectly flat.” Zazoun and Mahdjoub (2011, p. 63) also describes the upper boundary as being a “low-relief widespread erosional unconformity.” While Oard (1997, pp. 79) and Oard (2009a, p. 118) claim that the upper boundary shows “no evidence of a marine transgression”, the extensive evidence in Lüning et al. (2000) shows otherwise. Lüning et al. (2000) performed an in-depth review of the sedimentological, biostratigraphic, and organic geochemical evidence from the Ordovician-Silurian deposits over much of north Africa and into the Arabian Peninsula. Lüning et al. (2000, Figure 8, pp. 128-129) shows that the tops of the Late Ordovician glacial and periglacial deposits (Memouniat or Mamuniyat Formation, Libyan equivalent to the Tamadjert Formation; Le Heron et al. 2009, p. 63) in a cross-section from Morocco and into Algeria and Libya have “strong” paleorelief rather than being “flat.” Lüning et al. (2000, p. 131) further describes the extensive paleorelief on the boundary:

“In the earliest stages of the transgression, during the latest Ordovician persculptus Zone and the earliest Silurian Rhuddanian Stage, only low-lying areas of the shelf were flooded and shales deposited… [figure and references omitted] There is usually a sharp contact between Ordovician strata and the latest Ordovician–early Silurian shales. The North African and Arabian shelf at that time were characterized by a complex system of flooded intrashelf basins and palaeovalleys which were separated by various tectonic and sedimentary palaeohigh structures.”

The presence of paleovalleys and paleohighs indicates that the boundary was generally not flat and the sharpness of the contact between the eroded Ordovician deposits and the overlying shales is simply an unconformity (Zazoun and Mahdjoub 2011) – nothing unusual. Significantly, the paleohighs of the upper boundary were often high enough to have been barriers to open-ocean circulation, which explains the presence of anoxic black shales locally overlying the Late Ordovician glacial and periglacial deposits (Lüning et al. 2000, p. 137). Lüning et al. (2000, p. 138) also estimate the rate of the “extremely rapid” Silurian marine transgression:

“The latest Ordovician/earliest Silurian transgression in North Gondwana was extremely rapid, because the North African Shelf at that time represented a platform rather than a ramp. Within a few hundred thousand years the sea transgressed more than 1000 km inland, following a system of intrashelf palaeo-depressions.” [my emphasis]

So, the relief and nature of the upper boundary of the Tamadjert Formation, like the lower boundary, does nothing to refute actualism and support Flood Geology (Lüning et al. 2000; Zazoun and Mahdjoub 2011). Even if the upper boundary of the Tamadjert Formation was “flat”, what justification does Oard (1997, pp. 79-80) have to claim that this boundary is inconsistent with Ordovician glaciations when scientists fully recognize that the erosional boundary and its overlying rocks are post-glacial and not glacial?

After showing in my 1999 essay that the discussions of the upper and lower boundaries of the Tamadjert Formation in Oard (1997, pp. 78-80) were either irrelevant or based on inaccurate summaries of the literature, I discussed a number of other features in the Silurian deposits above the upper boundary that are consistent with a post-glacial rise in sea level and inconsistent with Noah’s Flood, including animal burrows. Oard (1997) should have addressed these issues. Rather than discussing how worms or other burrowing animals could have avoided burial and survived Ordovician “mass flows” in the middle of Noah’s Flood or providing even one reference from the “Flood geology literature” to explain how such burrows and similar features could form, Oard (2009a, p. 118) uses classic arm-waving tactics and tries to dismiss these serious problems for his Flood geology by calling them “smokescreens.” Rather than being “smokescreens”, my 1999 essay discusses some very relevant problems for the Flood scenario endorsed by Oard (1997):

“Bennacef et al. (1971, p. 2241) describe the shales as overlying a sandstone, where the top few centimeters of the sandstone have been borrowed. How did any critters get in the middle of rapidly deposited ‘Flood’ sediments and dig burrows before the shale was deposited? Ancient dunes, 20-30 meters wide, are present at the northern exposures of the Tassili N’Ajjer and probably formed in shallow near shore environments. Again, these features are incompatible with mass flows that were supposedly associated with deep, violent ‘Flood’ waters. Overall, the contact between the Tamadjert Formation and overlying Silurian shales is consistent with a marine transgression associated with the melting of glaciers. Bennacef et al. (1971, p. 2241) also cite boron analyses and other geochemical evidence from these deposits to support a glacial related rise in sea level.”

So, where were the Silurian marine burrowing animals hiding during the deposition of hundreds of meters of Cambrian and Ordovician sediments in Units II through IV? At Tassili-n-Ajjers, Algeria, these sediments are more than 500 meters thick (Zazoun and Mahdjoub 2011, p. 66, Figure 2). How did these animals avoid a quick burial and death during the deposition of the Cambrian and Ordovician sediments if they actually formed during Noah’s Flood? (See here and here for further insights into the problems that animal burrows create for Flood geology.) Also, how does Noah's Flood explain the boron analyses, which indicate a glacially related rise in sea level? Oard (2009a, p. 117-118) provides no rock solid answers to these fatal problems for Flood geology. He either ignores the details or misquotes the literature.

References

Allen, P., 1975, "Ordovician Glacials of the Central Sahara," in A.E. Wright and F. Moseley (eds.) Ice Ages: Ancient and Modern, Seel House Press, Liverpool, pp. 275-286.

Bennacef, A., S. Beuf, B. Biju-Duval, O. De Charpal, O. Gariel, and P. Rognon. 1971. "Example of Cratonic Sedimentation: Lower Paleozoic of Algerian Sahara," American Association of Petroleum Geologists Bulletin, v. 55, n. 12, December, pp. 2225-2245.

Biju-Duval, B., M. Deynoux, and P. Rognon, 1981, "Late Ordovician Tillites of the Central Sahara," in M.J. Hambrey and W.B. Harland (eds.) Earth’s Pre-Pleistocene Glacial Record, Cambridge University Press, London, pp. 99-107.

Denis, M., J.-F. Buoncristiani, M. Kontaté, and M. Guiraud. 2007. “The Origin and Glaciodynamic Significance of Sandstone Ridge Networks from the Hirnantian Glaciation of the Djado Basin (Niger)”, Sedimentology, v. 54, pp. 1225-1243.

Deschamps, R., R. Eschard, and S. Rousse. 2013. "Architecture of Late Ordovician Glacial Valleys in the Tassili N'Ajjer Area (Algeria)," Sedimentary Geology, v. 289, pp. 124-147.

Deynoux, M., 1985, "Terrestrial or Waterlain Glacial Diamictites? Three Case Studies from the Late Precambrian and Late Ordovician Glacial Drifts in West Africa," Palaeogeography, Palaeoclimatology, Palaeoecology, v. 51, pp. 97-141.

Deynoux M. and R. Trompette. 1981. "Late Ordovician Tillites of the Taoudeni Basin, West Africa," in M.J. Hambrey and W.B. Harland (eds.) "Earth’s Pre-Pleistocene Glacial Record," Cambridge University Press, London, pp. 89-96.

Fairbridge, R.W. 1979. "Traces from the Desert: Ordovician," in B.S. John (ed.), Winters of the World, John Wiley & Sons, New York, pp. 131-153.

Frakes, L.A., 1979, Climates throughout Geologic Time, Elsevier, New York.

Krabbendam, M. and T. Bradwell. 2014. "Quaternary Evolution of Glaciated Gneiss Terrains: Pre-Glacial Weathering vs. Glacial Erosion", Quaternary Science Reviews, v. 95, pp. 20-42.

Le Heron, D. P., J. Craig, and J. L. Etienne. 2009. “Ancient Glaciations and Hydrocarbon Accumulations in North Africa and the Middle East”, Earth-Science Reviews v. 93, n. 3-4, pp. 47-76.

Le Heron, D.P. 2010. “Trace Fossils on a Late Ordovician Glacially Striated Pavement in Algeria”, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 297, pp. 138-143.

Lüning, S., J. Craig, D.K. Loydell, P. Štorch, and B. Fitches. 2000. “Lower Silurian ‘Hot Shales’ in North Africa and Arabia: Regional Distribution and Depositional Model,” Earth-Science Reviews, v. 49, pp. 121-200.

Oard, M.J. 1997. Ancient Ice Ages or Gigantic Submarine Landsides? Creation Research Society, Monograph No. 5, Chino Valley, AZ.

Oard, M.J. 2009a. “Landslides Win in a Landslide over Ancient 'Ice Ages'“, chapter 7 in M.J. Oard and J.K. Reed (editors). 2009. Rock Solid Answers: The Biblical Truth Behind 14 Geological Questions, Master Books: Green Forest, AR, pp. 111-123.

Schermerhorn, L.J.G. 1970. “Saharan Ice”, Geotimes, v. 15, pp. 7-8.

Zazoun, R.S. and Y. Mahdjoub. 2011. Strain Analysis of Late Ordovician Tectonic Events in the In-Tahouite and Tamadjert Formations (Tassili-N-Ajjers Area, Algeria). Journal of African Earth Sciences v. 60, n. 3, pp: 63-78.