Ordovician Glaciations

The Cold and Hard Evidence of Ordovician Glaciations Continues to Accumulate and Bury Flood Geology

Kevin R. Henke, Ph.D.

May 4, 2014, Updated April 5, 2022

Mr. Oard Ignores Abundant 21^st Century Evidence for Ordovician Glaciations

Glaciations occurred around the South Pole of Gondwana (now North Africa) during the Late Ordovician and into the Early Silurian (Finnegan et al., 2011). Table 1 in Oard (2009a, p. 111) dates these glaciations at about 429 to 445 million years ago (Crowell 1999, pp. 1-2). Finnegan et al. (2011, p. 904) estimated that the maximum extent of the Late Ordovician glaciers was about 444 million years ago during the Hirnantian stage.

Like Oard (1997), Oard (2009a, p. 111) still believes that the evidence of Ordovician glaciations is disappearing:

“Features he [Dr. Henke] insists are the result of an Ordovician 'ice age' are now thought to be of non-glacial origin.”

Oard (2009a, p. 119) also ends his section on the Ordovician glaciations with a wish that has absolutely no basis in reality:

“At the current rate, reinterpretation of supposed glaciogenic features as products of non-glacial processes will soon show that there is no 'evidence' for the Ordovician 'ice age.'“

So where are the 21st century Schermerhorns, Mr. Oard? While 21^st century geologists are still debating the number and length of the Ordovician glaciations and continue to argue over the glacial origins of individual pre-Pleistocene outcrops (e.g., Chumakov, 2008, pp. 108-109), none of them have any doubts that the Ordovician glaciations occurred. Current research simply does not support the desire of Oard (2009a, p. 119) for the abundant field evidence of the Late Ordovician glaciations to be transformed into marine Flood deposits. The existence of Ordovician glaciations is firmly established by diverse structural, paleontological, paleomagnetic and stable isotope studies, which are beautifully summarized in Denis et al. (2007), Ghienne (2003) and other 21st century science references. The following titles are just a few examples of 21st century geology articles that continue to provide ample evidence and support for the existence of Late Ordovician cold climates and continental glaciations, while at the same time refuting Mr. Oard's imaginary desires that the evidence would just disappear:

Young et al. (2004) “Geochemistry and Palaeogeography of Upper Ordovician Glaciogenic Sedimentary Rocks in the Table Mountain Group, South Africa”

El-ghali (2005) “Depositional Environments and Sequence Stratigraphy of Paralic Glacial, Paraglacial and Postglacial Upper Ordovician Siliciclastic Deposits in the Murzuq Basin, SW Libya”

Gutiérrez-Marco et al. (2010) “Did the Late Ordovician African Ice Sheet Reach Europe?”

Hirst et al. (2002) “Tunnel Valleys and Density Flow Processes in the Upper Ordovician Glacial Succession, Illizi Basin, Algeria: Influence on Reservoir Quality”

Ghienne et al. (2003) “Paleovalleys and Fault-controlled Depocentres in the Late-Ordovician Glacial Record of the Murzuq Basin (central Libya)”

Ghienne (2003) “Late Ordovician Sedimentary Environments, Glacial Cycles, and Post-Glacial Transgression in the Taoudeni Basin, West Africa”

Moreau et al. (2005) “440 Ma Ice Stream in North Africa”

Denis et al. (2007) “The Origin and Glaciodynamic Significance of Sandstone Ridge Networks from the Hirnantian Glaciation of the Djado Basin (Niger)”

El-ghali et al. (2006) “Distribution of Diagenetic Alterations in Glaciogenic Sandstones within a Depositional Facies and Sequence Stratigraphic Framework: Evidence from the Upper Ordovician of the Murzuq Basin, SW Libya”

Le Heron et al. (2010) “Glaciation and Deglaciation of the Libyan Desert: The Late Ordovician Record”

Le Heron (2010) “Interpretation of Late Ordovician Glaciogenic Reservoirs from 3-D Seismic Data: An Example from the Murzuq Basin, Libya”

Le Heron and Dowdeswell (2009) “Calculating Ice Volumes and Ice Flux to Constrain the Dimensions of a 440 Ma North African Ice Sheet”

Le Heron and Howard (2010) “Evidence for Late Ordovician Glaciation of Al Kufrah Basin, Libya”

Kumpulainen et al. (2006) “Trace Fossil Evidence from the Adigrat Sandstone for an Ordovician Glaciation in Eritrea, NE Africa”

Le Heron et al. (2009) “Ancient Glaciations and Hydrocarbon Accumulation in North Africa and the Middle East”

Turner et al. (2005) “Late Ordovician (Ashgillian) Glacial Deposits in Southern Jordan”

Armstrong et al. (2009) “Response of the Inter-tropical Convergence Zone to Southern Hemisphere Cooling during Upper Ordovician Glaciation”

Loi et al. (2010) “The Late Ordovician Glacio-eustatic Record from a High-latitude Storm-dominated Shelf Succession: The Bou Ingarf Section (Anti-Atlas, Southern Morocco)”

Finlay et al. (2010) “Tracking the Hirnantian Glaciation using Os Isotopes”

Le Heron et al. (2007) “Maximum Extent of Ice Sheets in Morocco during the Late Ordovician Glaciation”

Le Heron (2007) “Late Ordovician Glacial Record of the Anti-Atlas, Morocco”

Le Heron and Craig (2008) “First-order Reconstructions of a Late Ordovician Saharan Ice Sheet”

Delabroye and Vecoli (2010) “The End-Ordovician Glaciation and the Hirnantian Stage: A Global Review and Questions about Late Ordovician Event Stratigraphy”

Cherns and Wheeley (2007) “A Pre-Hirnantian (Late Ordovician) Interval of Global Cooling - The Boda Event Re-assessed”

Brenchley et al. (2003) “High-resolution Stable Isotope Stratigraphy of Upper Ordovician Sequences: Constraints on the Timing of Bioevents and Environmental Changes Associated with Mass Extinction and Glaciation”

Raymond and Metz (2004) “Ice and its Consequences: Glaciation in the Late Ordovician, Late Devonian, Pennsylvanian-Permian, and Cenozoic Compared”

Lefebvre et al. (2010) “Did a Katian Large Igneous Province Trigger the Late Ordovician Glaciation? A Hypothesis Tested with a Carbon Cycle Model”

Herrmann et al. (2004) “Response of Late Ordovician Paleoceanography to Changes in Sea Level, Continental Drift, and Atmospheric pCO₂: Potential Causes for Long-term Cooling and Glaciation”

Le Heron et al. (2005) “The Origins of Glacially Related Soft-sediment Deformation Structures in Upper Ordovician Glaciogenic Rocks: Implication for Ice-Sheet Dynamics”

Finnegan et al. (2011) “The Magnitude and Duration of Late Ordovician-Early Silurian Glaciation”

Deschamps et al. (2013) "Architecture of Late Ordovician Glacial Valleys in the Tassili N'Ajjer Area (Algeria)"

Dronov (2013) "Late Ordovician Cooling Event: Evidence from the Siberian Craton"

Elrick et al. (2013) "Orbital-scale Climate Change and Glacioeustasy during the Early Late Ordovician (pre-Hirnantian) Determined from δ¹⁸O Values in Marine Apatite"

Holmden et al (2013) "Nd Isotope Records of Late Ordovician Sea-level Change - Implications for Glaciation Frequency and Global Stratigraphic Correlation"

Dabard et al. (2015) "Sea-level Curve for the Middle to Early Late Ordovician in the Armorican Massif (western France): Icehouse Third-order Glacio-eustatic Cycles"

Girard et al.(2015) "Sedimentary Imprints of Former Ice-sheet Margins: Insights from an End-Ordovician Archive (SW Libya)"

Kroeger et al. (2015) "Subaerial Speleothems and Deep Karst in Central Sweden Linked to Hirnantian Glaciations"

Luo et al. (2016) "Perturbation of the Marine Nitrogen Cycle during the Late Ordovician Glaciation and Mass Extinction"

Pohl et al. (2016) "Glacial Onset Predated Late Ordovician Climate Cooling"

Masri (2017) "Late Ordovician Glacial and Glacio-fluvial Paleovalley Architecture and Sedimentation in Southeast Jordan and Northwest Saudi Arabia"

Lewin et al. (2018) "Provenance of Sandstones in Ethiopia during Late Ordovician and Carboniferous-Permian Gondwana Glaciations Petrography and Geochemistry of the Enticho Sandstone and the Edaga Arbi Glacials"

Ghienne et al. (2018) The impact of the end-Ordovician glaciation on sediment routing systems: A case study from the Meseta (northern Morocco)

Creveling et al. (2018) Spatial variation in Late Ordovician Glacioeustatic Sea-level Change

Hinnov and Diecchio (2020) Upper Ordovician Juniata Formation, Central Appalachian Basin, USA: A record of Milankovitch-forced Eustatic Oscillations Originating from Glaciations in Polar Gondwana

Makled et al. (2021) Organic petrography of Ordovician - Silurian rocks and their implications to hydrocarbon generation in the Akkas-1 well, western Iraq: New evidence for the Ordovician Gloeocapsomorpha and glaciation events.

Zhang et al. (2021) Climate Change in the Subtropical Paleo-Tethys before the Late Ordovician Glacation.

Rather than summarizing these articles, I would encourage readers to directly review them and see for themselves the enormous amount of evidence for Ordovician glaciations.

As further seen in the following quotations, 21^st century field and laboratory evidence continues to support the existence of Ordovician glaciations. Le Heron and Howard (2010) state:

“Fieldwork at the flanks of Al Kufrah Basin, Libya, reveals that Late Ordovician ice sheets were present in the eastern Sahara and that they extended northeastward toward Egypt.”

Finlay et al. (2010) use osmium and carbon isotopes to track the onset and end of the Late Ordovician (Hirnantian) glaciation. They conclude:

“Thus, by coupling Os_i and δ¹³C_org proxies we provide the most direct evidence for the initiation and cessation of the Hirnantian [Ordovician] glaciation.”

Armstrong et al. (2009) also used stable isotopes from carbonate rocks and fossils to identify climatic changes during the Late Ordovician. Armstrong (2009, p. 228) describe the Ordovician as having long-term (10's of millions of years) general declines in both atmospheric CO₂ and global temperatures punctuated with shorter climatic changes, none of which is compatible with Noah's Flood.

While Oard (2009a) wishes that the evidence for Ordovician glaciations would just melt away, Loi et al. (2010) recently concluded that the Gondwana glaciers were more extensive in time than previously realized:

“Evidences of glaciation at the end of the Ordovician are widespread in western Gondwana. Some authors consider the glaciation was restricted to the Hirnantian time, but occurrences of glacial deposits in the Lower Silurian strata of South America indicate that the Gondwana glaciers did not completely disappear after the Hirnantian glaciation. In addition, numerous studies based on palaeoeocology, sedimentology, sequence stratigraphy and stable isotopes have suggested that ice sheets formed as soon as the Early/Middle Katian.”

Le Heron et al. (2010, p. 117) also conclude:

“In SE Al Kufrah Basin [Libya], the evidence for glaciation is thus strong. Therefore, sedimentary models in this area should consider a strong ice sheet influence on sedimentation.” [my emphasis]

Ordovician glaciations were also far more extensive geographically than previously realized. As one example, the following are some recent statements on newly recognized Late Ordovician glacial deposits in Morocco. Le Heron et al. (2007, p. 200) states:

“New field data demonstrate that during the Late Ordovician (Hirnantian) glaciation, an ice sheet expanding northwestwards over the Anti-Atlas range reached into the southern Meseta of northern Morocco.”

Le Heron et al. (2007, p. 221) also conclude:

“The occurrence of subglacial deformation structures in the High Atlas of Marrakech and the Rehamna inliers extends the ice sheet at least 200 km beyond the northernmost occurrences of striated surfaces reported by previous authors...[references omitted], or 150 km north of the most distal glaciotectonic folds and thrusts... [references omitted] or glacial valleys... [references omitted].”

Other recent studies in southern Europe (Gutiérrez-Marco et al., 2010) and possibly Turkey (Monod et al., 2003) indicate the presence of Ordovician glaciations. Thus, since Oard (1997), the supporting evidence for Late Ordovician glaciations has been increasing and growing stronger, and not disappearing as Mr. Oard hopes.

Although 21^st century geologists might disagree about whether a particular feature formed from one glacial process or another, they usually agree that glaciers were directly or indirectly responsible. As Le Heron et al. (2009, p. 61) stated about some of the Ordovician glacial features in northern Africa:

“Whilst the precise interpretation of some of these [glacial] features has not stood the test of time (valley glacier incisions have been reinterpreted as tunnel valleys, for instance... [references omitted]) and pingos reinterpreted as circular features produced by mud diapirism...[reference omitted], the wealth of evidence remains in support of a large ice sheet having glaciated the Sahara 443 Myr ago...[reference to figure omitted].” [my emphasis]

On the basis of these overwhelming data, it’s no wonder that Le Heron et al. (2009, p. 61) in their recent summary of ancient glaciations concludes the following, which flatly crushes young-Earth creationist (YEC) delusions of the soon demise of the Ordovician glaciations:

“The physical evidence for Late Ordovician glaciation in the Sahara and the Arabian Peninsula is excellent.”

This is the consensus of a team of scientists that have studied these Ordovician deposits for years. At the same time, I'm sure that if a 21st century Schermerhorn exists (that is, a secular geologist that is skeptical of one or more pre-Pleistocene glaciations and argues that all of the glacial deposits could in fact be non-glacial), Mr. Oard would have found that person's articles and extensively quoted him or her in Oard (2009a) and Oard (2009b). However, Oard (2009a) and Oard (2009b) do not cite a single 21st century secular geologist that denies the existence of the Ordovician, Late Paleozoic or Late Precambrian glaciations.

Even the 21^st Century Geological References in Oard (2009a,b) Unequivocally Refute his YEC Agenda

Like Oard (1997), the most recent references in Oard (2009a) and Oard (2009b) often contain important statements that categorically refute his Flood geology agenda. Unfortunately, Mr. Oard inappropriately chooses to hide these statements from his readers. For example, when Oard (2009a, p. 119) cited Ghienne (2003), he failed to mention that Ghienne (2003, p. 117) states the following:

“The sedimentary record and worldwide palaeontological and isotopic data support the existence of short-lived latest Ordovician (Hirnantian) ice sheets over western Gondwanaland.”

Ghienne (2003, p. 140) also states:

“Palaeontological data suggest that the Late Ordovician glaciation was restricted to the lower part of the Hirnantian (Extraordinarius zone), which was estimated to have lasted 0.5-1 m.y. [million years]... [references omitted]. This time-slice would conform to the time represented by the Late Ordovician glacial record in the Taoudeni Basin, which comprises four cycles of possibly 100 k.y. [100,000 years]. This is a minimal value for the duration of the glaciation of the northern Gondwanaland as other, non-recorded, glacial cycles may have occurred.” [my emphasis]

Ghinne and Deynoux (1998, p. 141-142), another reference in the bibliography of Oard (2009a), concludes:

“Work by petroleum geologists and scientists of the University of Dakar in the late 1950's and 1960's resulted in unequivocal evidence for an Ordovician glaciation...[references omitted].” [my emphasis]

“There are now well-documented glacial and related deposits associated with an early Palaeozoic glaciation in Africa (North and South), the Arabian Peninsula, Europe, eastern North America and South America... [references omitted].” [my emphasis]

Thus, Mr. Oard's proclamation in Oard (2009a, pp. 117-119, 121) that there is no evidence of Late Ordovician glaciations and that his Flood geology remains “intact” are flatly refuted by the very references that he used in Oard (2009a). Mr. Oard in Oard (2009a) and Oard (2009b) is simply closing his eyes and refusing to look at reality. Mr. Oard’s habit of misrepresenting the scientific literature is just like a “salvation by works” Christian quoting James and completely ignoring the grace verses of Romans and Ephesians.

Rather than deal with the overwhelming evidence for pre-Pleistocene glaciations that continues to accumulate, Oard (2009a, p. 114) feels that his submarine landslide interpretations are “plausible” alternative explanations for pre-Pleistocene glaciations, and that I've being subjective for rejecting them. However, as I stated in my 1999 essay, many examples in Oard (1997) show that he quotes references out of context, misrepresents actualism, and proposes submarine landslide interpretations that just don't comply with the field evidence. Mr. Oard might want people to believe that I'm unfairly picking on him and that he actually has an equally valid interpretation involving Flood geology. However, the abundant evidence in the above 21^st century scientific articles continues to show otherwise. As just one example, Denis et al. (2007) considered various non-glacial hypotheses to explain sandstone ridges and other field evidence from the Djado Basin, Niger, but concluded that the evidence supports a Late Ordovician glaciation. Furthermore, Denis et al. (2007, p. 1231) found ice crystal imprints among dropstones, striations, sandstone ridges of probable subglacial origin (comparable with eskers, p. 1241) and other glacial features in the Late Ordovician glacial deposits of the Djado Basin of Niger, Africa. Now, under extreme aridity, sulfate salts may produce patterns that resemble ice crystal imprints (Girard et al. 2015, p. 278) and perhaps biological activity might produce similar patterns, but how would water-soluble salts forming under very dry conditions and organisms mimic ice patterns during a Noah's Flood?

Under the rigorous scrutiny that Oard (2009a, p. 121) claims to advocate, the evidence for pre-Pleistocene glaciations is now stronger than ever. By ignoring the contents of these numerous relevant 21^st century articles, Oard (2009a, pp. 117-119) fails to provide any “update” on Ordovician glaciations and is entirely mistaken when he claims that the geologic data published since 1997 supports Noah's Flood. Flood geology is not rising from its 19^th century grave. It's as dead as ever.

References

Armstrong, H. A., J. Baldini, T. J. Challands, D. R. Gröcke, and A. W. Owen. 2009. “Response of the Inter-tropical Convergence Zone to Southern Hemisphere Cooling during Upper Ordovician Glaciation”, Palaeogeography, Palaeoclimatology, Palaeoecology v. 284, n.3-4, pp. 227-236.

Brenchley, P.J., G.A. Carden, L. Hints, D. Kaljo, J.D. Marshall, T. Martma, T. Meidla, and J. Nolvak. 2003. “High-resolution Stable Isotope Stratigraphy of Upper Ordovician Sequences: Constraints on the Timing of Bioevents and Environmental Changes Associated with Mass Extinction and Glaciation”, GSA Bulletin, v. 115, n. 1, pp. 89-104.

Cherns, L. and J.R. Wheeley. 2007. “A Pre-Hirnantian (Late Ordovician) Interval of Global Cooling - The Boda Event Re-assessed”, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 251, pp. 449-460.

Chumakov, N.M. 2008. “A Problem of Total Glaciations on the Earth in the Late Precambrian”, Stratigraphy and Geological Correlation, v. 16, n. 2, pp. 107-119.

Creveling, J.R., S. Finnegan, J.X. Mitrovica, and K.D. Bergmann. (2018) Spatial Variation in Late Ordovician Glacioeustatic Sea-level Change, Earth and Planetary Science Letters, v. 496, pp. 1-9.

Crowell, J.C. 1999. Pre-Mesozoic Ice Ages: Their Bearing on Understanding the Climate System, Geological Society of America Memoir, 192, Boulder, Colorado, USA, 106pp.

Dabard, M.P., A. Loi, F. Paris, J.F. Ghienne, M. Pistis, and M. Vidal. 2015. "Sea-level Curve for the Middle to Early Late Ordovician in the Armorican Massif (western France): Icehouse Third-order Glacio-eustatic Cycles", Palaeogeography, Palaeoclimatology, Palaeoecology, v. 436, pp. 96-111.

Delabroye, A. and M. Vecoli. 2010. “The End-Ordovician Glaciation and the Hirnantian Stage: A Global Review and Questions about Late Ordovician Event Stratigraphy”, Earth-Science Reviews v. 98, n. 3-4, pp: 269-282.

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.

Dronov, A. 2013. "Late Ordovician Cooling Event: Evidence from the Siberian Craton," Palaeogeography, Palaeoclimatology, Palaeoecology, v. 389, pp. 87-95.

El-ghali, M.A.K. 2005. “Depositional Environments and Sequence Stratigraphy of Paralic Glacial, Paraglacial and Postglacial Upper Ordovician Siliciclastic Deposits in the Murzuq Basin, SW Libya”, Sedimentary Geology v. 177, n. 3-4, pp. 145-173.

El-ghali, M.A.K, H. Mansurbeg, S. Morad, I. Al-Aasm, and K. Ramseyer. 2006. “Distribution of Diagenetic Alterations in Glaciogenic Sandstones with a Depositional Facies and Sequence Stratigraphic Framework: Evidence from the Upper Ordovician of the Murzuq Basin, SW Libya”, Sedimentary Geology, v. 190, pp. 323-351.

Elrick, M., D. Reardon, W. Labor, J. Martin, A. Desrochers, and M. Pope. 2013. "Orbital-scale Climate Change and Glacioeustasy during the Early Late Ordovician (pre-Hirnantian) Determined from δ¹⁸O Values in Marine Apatite," Geology, v. 41, no. 7, pp. 775-778.

Finlay, A. J., D. Selby, and D. R. Gröcke. 2010. “Tracking the Hirnantian Glaciation Using Os Isotopes”, Earth and Planetary Science Letters, v. 293, n. 3-4, pp. 339-348.

Finnegan, S., K. Bergmann, J.M. Eiler, D.S. Jones, D.A. Fike, I. Eisenman, N.C. Hughes, A. K. Tripati, W.W. Fischer. 2011. “The Magnitude and Duration of Late Ordovician-Early Silurian Glaciation”, Science, v. 331, Feb. 18, pp. 903-906.

Ghienne, J.-F. 2003. “Late Ordovician Sedimentary Environments, Glacial Cycles, and Post-glacial Transgression in the Taoudeni Basin, West Africa”, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 189, pp. 117-145.

Ghienne, J.F. and M. Deynoux. 1998. “Large-scale Channel Fill Structures in Late Ordovician Glacial Deposits in Mauritania, Western Sahara”, Sedimentary Geology, v. 119, pp. 141-159.

Ghienne, J.F., M. Deynoux, G. Manatschal, and J.L. Rubino. 2003. “Palaeovalleys and Fault-controlled Depocenters in the Late-Ordovician Glacial Record of the Murzuq Basin (Central Libya)”, Compes Rendus Geoscience, v. 335, pp. 1,091-1,100.

Ghienne, J.-F., A. Benvenuti, M. El Houicha, F. Girard, E. Kali, Y. Khoukhi, C. Langbour, T. Magna, J. Míková, A. Moscariello, and K. Schulmann, The impact of the end-Ordovician glaciation on sediment routing systems: A case study from the Meseta (northern Morocco) Gondwana Research, v. 63, pp. 169-178.

Girard, F., J.-F. Ghienne, X. Du-Bernard, and J.-L. Rubino. 2015. "Sedimentary Imprints of Former Ice-sheet Margins: Insights from an End-Ordovician Archive (SW Libya)", Earth-Science Reviews, v. 148, pp. 259-289.

Gutiérrez-Marco, J. C., J.-F Ghienne, E. Bernárdez, and M. P. Hacar. 2010. “Did the Late Ordovician African Ice Sheet Reach Europe?”, Geology v. 38, n. 3, pp. 279-282.

Herrmann, A. D., B. J. Haupt, M. E. Patzkowsky, D. Seidov, and R. L. Slingerland. 2004. “Response of Late Ordovician Paleoceanography to Changes in Sea Level, Continental Drift, and Atmospheric pCO₂: Potential Causes for Long-term Cooling and Glaciation”, Palaeogeography, Palaeoclimatology, Palaeoecology v. 210, n. 2-4, pp. 385-401.

Hinnov, L.A. and R.J. Diecchio. 2020. "Upper Ordovician Juniata Formation, Central Appalachian Basin, USA: A record of Milankovitch-forced Eustatic Oscillations Originating from Glaciations in Polar Gondwana", Special Paper of the Geological Society of America, n. 545, 17pp.

Hirst, J.P.P., A. Benbakir, D. F. Payne, and I. R. Westlake. 2002. “Tunnel Valleys and Density Flow Processes in the Upper Ordovician Glacial Succession, Illizi Basin, Algeria: Influence on Reservoir Quality”, Journal of Petroleum Geology v. 25, n. 3, pp. 297-324.

Holmden, C., C.E. Mitchell, D.F. LaPorte, W.P. Patterson, M.J. Melchin, and S.C. Finney. 2013. "Nd Isotope Records of Late Ordovician Sea-level Change - Implications for Glaciation Frequency and Global Stratigraphic Correlation." Palaeogeography, Palaeoclimatology, Palaeoecology v. 386, pp. 131-144.

Luo, G., A.J. Algeo, R. Zhan, D. Yan, J. Huang, J. Liu, S. Xie. 2016. "Perturbation of the Marine Nitrogen Cycle during the Late Ordovician Glaciation and Mass Extinction",

Palaeogeography, Palaeoclimatology, Palaeoecology, 448, pp. 339-348.

Kroeger, B., J.O.R. Ebbestad, O. Lehnert, C.V. Ullmann, C. Korte, R. Frei, and C.M.0. Rasmussen. 2015. "Subaerial Speleothems and Deep Karst in Central Sweden Linked to Hirnantian Glaciations", Journal of the Geological Society, v. 172, pp. 349-356.

Kumpulainen, R. A., A. Uchman, B. Woldehaimanot, T. Kreuser, and S. Ghirmay. 2006. “Trace Fossil Evidence from the Adigrat Sandstone for an Ordovician Glaciation in Eritrea, NE Africa”, Journal of African Earth Sciences v. 45, n. 4-5, pp. 408-420.

Lefebvre, V., T. Servais, L. François, and O. Averbuch. 2010. “Did a Katian Large Igneous Province Trigger the Late Ordovician Glaciation? A Hypothesis Tested with a Carbon Cycle Model”, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 296, n. 3-4, pp. 310-319.

Le Heron, D.P. 2007. ”Late Ordovician Glacial Record of the Anti-Atlas, Morocco”, Sedimentary Geology v. 201, n. 1-2, pp. 93-110.

Le Heron, D. P. 2010. “Interpretation of Late Ordovician Glaciogenic Reservoirs from 3-D Seismic Data: An Example from the Murzuq Basin, Libya”, Geological Magazine v. 147, n.1, pp. 28-41.

Le Heron, D. P., H. A. Armstrong, C. Wilson, J. P. Howard, and L. Gindre. 2010. “Glaciation and Deglaciation of the Libyan Desert: The Late Ordovician Record”, Sedimentary Geology v. 223, n.1-2, pp. 100-125.

Le Heron, D. P., and J. Craig. 2008. First-order Reconstructions of a Late Ordovician Saharan Ice Sheet”, Journal of the Geological Society v. 165, n. 1, pp. 19-29.

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., and J. A. Dowdeswell. 2009. “Calculating Ice Volumes and Ice Flux to Constrain the Dimensions of a 440 Ma North African Ice Sheet”, Journal of the Geological Society v. 166, n. 2, pp. 277-281.

Le Heron, D. P., J. -F Ghienne, M. El Houicha, Y. Khoukhi, and J. -L Rubino. 2007. “Maximum Extent of Ice Sheets in Morocco during the Late Ordovician Glaciation”, Palaeogeography, Palaeoclimatology, Palaeoecology v. 245, n. 1-2, pp. 200-226.

Le Heron, D. P., and J. Howard. 2010. “Evidence for Late Ordovician Glaciation of Al Kufrah Basin, Libya”, Journal of African Earth Sciences v. 58, n. 2, pp. 354-364.

Le Heron, D. P., O. E. Sutcliffe, R. J. Whittington, and J. Craig. 2005. “The Origins of Glacially Related Soft-sediment Deformation Structures in Upper Ordovician Glaciogenic Rocks: Implication for Ice-sheet Dynamics”, Palaeogeography, Palaeoclimatology, Palaeoecology v. 218, n. 1-2, pp. 75-103.

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Loi, A., J.-F. Ghienne, M.P. Dabard, F. Paris, A. Botquelen, N. Christ, Z. Elaouad-Debbaj, A. Gorini, M. Vidal, B. Videt, and J. Destombes. 2010. “The Late Ordovician Glacio-eustatic Record from a High-latitude Storm-dominated Shelf Succession: The Bou Ingarf Section (Anti-Atlas, Southern Morocco)”, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 296, pp. 332-358.

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