Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-17T20:00:53.372Z Has data issue: false hasContentIssue false
  • English
  • Français

Interpretation of Late Ordovician glaciogenic reservoirs from 3-D seismic data: an example from the Murzuq Basin, Libya

Published online by Cambridge University Press:  13 November 2009

DANIEL PAUL LE HERON
DANIEL PAUL LE HERON*
Affiliation:
Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
*
*E-mail: d.leheron@es.rhul.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

Understanding the recessional behaviour of ancient pre-Cenozoic ice sheets based on seismic reflection studies is generally difficult through scarcity of data. In North Africa, however, hydrocarbon exploration has produced high quality seismic reflection datasets that permit an analysis of the morphology and internal sedimentary architecture of incisions of Late Ordovician age related to the Hirnantian glaciation. Analysis of a high-resolution 3-D seismic dataset covering a small area in western Libya (the N Murzuq Basin) reveals a sharply defined, WNW–ESE-oriented palaeo-escarpment, with a higher (cliff-forming) western margin and a lower (basin-forming) eastern margin. The palaeo-escarpment defines the western flank of a sub-basin extending up to 60 km in width, known as the Awbari Trough. The escarpment and the trough are interpreted as the morphological expression of a major unconformity dividing pre-glacial sediments below from Late Ordovician (?Hirnantian) glacially related sediments above. Two hypotheses are considered for the origins of both the escarpment and the Awbari Trough: (1) as a tectonic feature such as a half graben that was active during sedimentation and (2) a glacially related palaeotopography, with the latter interpretation preferred, owing to the lack of evidence for syn-sedimentary fault activity. The width of the Awbari Trough compares to the large-scale cross-shelf troughs in modern high latitude settings, such as the Barents Shelf, produced by ice streams. The Awbari Trough was progressively filled in by gravity flow deposits throughout the course of the glaciation, until the initial incision became filled in with sediments during an overall glacial retreat phase and ceased to influence sedimentation patterns. Glacial re-advance across the basin produced a second unconformity observed in seismic data. Above this unconformity, meltwater processes incised a shallow (~ 20 m) and wide (~ 5 km) subglacial tunnel valley. Stabilization of the ice front prior to its ultimate retreat resulted in the deposition of a delta complex prior to the Early Silurian transgression.

Keywords

glacialseismicLibyaOrdovicianHirnantian
Type
Original Article
Information
Geological Magazine , Volume 147 , Issue 1 , January 2010 , pp. 28 - 41
Copyright
Copyright © Cambridge University Press 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Adamson, K., Glover, T., Whittington, R. & Craig, J. 2000. The Lower Devonian succession of the Murzuq Basin; possible indicators of eustatic and tectonic controls on sedimentation. In Geological exploration in Murzuq Basin (eds Sola, M. & Worsley, D.), pp. 431–47. Amsterdam: Elsevier.CrossRefGoogle Scholar
Andreassen, K., Nilssen, L. C., Rafaelsen, B. & Kuilman, L. 2004. Three-dimensional seismic data from the Barents Sea margin reveal evidence of past ice streams and their dynamics. Geology 32, 729–32.CrossRefGoogle Scholar
Aziz, A. 2000. Stratigraphy and hydrocarbon potential of the lower Palaeozoic succession of licence NC115, Murzuq Basin, SW Libya. In Geological exploration in Murzuq Basin (eds Sola, M. & Worsley, D.), pp. 485–509. Amsterdam: Elsevier.Google Scholar
Bellini, E. & Massa, D. 1980. A stratigraphic contribution to the Paleozoic of the southern basins of Libya. In The Geology of Libya I (eds Salem, M. J. & Busrewil, M. T.), pp. 3–56. London: Academic Press.Google Scholar
Beuf, S., Biju-Duval, B., de Charpal, O., Rognon, P., Gariel, O. & Bennacef, A. 1971. Les Gres du Palaeozoique inferieur au Sahara. Publications de l'Institut Français du Pétrole, Science et Technique du Pétrole 18, 1–464.Google Scholar
Bhattacharya, J. P. & Giosan, L. 2003. Wave-influenced deltas: geomorphological implications for facies reconstruction. Sedimentology 50, 187–210.CrossRefGoogle Scholar
Bhattacharya, J. P. & Walker, R. G. 1992. Deltas. In Facies Models: Response to Sea-Level Change (eds Walker, R. G. & James, N. P.), pp. 157–77. Geological Association of Canada, St Johns.Google Scholar
Brenchley, P. J., Marshall, J. D., Harper, D. A. T., Buttler, C. J. & Underwood, C. J. 2006. A Late Ordovician (Hirnantian) karstic surface in a submarine channel, recording glacio-eustatic sea-level changes; Meifod, central Wales. Geological Journal 41 (1), 1–22.CrossRefGoogle Scholar
Catuneanu, O. 2006. Principles of Sequence Stratigraphy. Oxford: Elsevier, 375 pp.Google Scholar
Cheel, R. J. & Leckie, D. A. 1993. Hummocky Cross-Stratification. In Sedimentology Review 1 (ed. Wright, V. P.), pp. 103–22. Wiley-Blackwell.CrossRefGoogle Scholar
Davidson, L., Beswetherick, S., Craig, J., Eales, M., Fisher, A., Himmali, A., Jho, J., Mejrab, B. & Smart, J. 2000. The structure, stratigraphy and petroleum geology of the Murzuq Basin, southwest Libya. In Geological exploration in Murzuq Basin (eds Sola, M. & Worsley, D.), pp. 295–320. Amsterdam: Elsevier.CrossRefGoogle Scholar
Deynoux, M. & Ghienne, J.-F. 2004. Late Ordovician glacial pavements revisited – a reappraisal of the origin of striated surfaces. Terra Nova 16, 95–101.CrossRefGoogle Scholar
Echikh, K. & Sola, M. A. 2000. Geology and Hydrocarbon occurrences in the Murzuq Basin SW Libya. In Geological exploration in Murzuq Basin (eds Sola, M. & Worsley, D.), pp. 175–222. Amsterdam: Elsevier.CrossRefGoogle Scholar
Ehlers, J. 1981. Problems of the Saalian stratigraphy in the Hamburg area. In Glacigenic deposits in the southwest parts of the Scandinavian Ice Sheet; Third conference of the Regional Group of the INQUA Commission (eds Ehlers, J. & Zandstra, J. D.), pp. 26–9. Mededelingen Rijks Geologische Dienst 34(1–11).Google Scholar
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 177, 145–73.CrossRefGoogle Scholar
Eschard, R., Abdallah, H., Braik, F. & Desaubliaux, G. 2005. The Lower Palaeozoic succession in the Tassili outcrops, Algeria: sedimentology and sequence stratigraphy. First Break 23, 27–36.CrossRefGoogle Scholar
Gani, R. M. 2004. From turbid to lucid; a straightforward approach to sediment gravity flows and their deposits. The Sedimentary Record 2 (3), 4–8.CrossRefGoogle Scholar
Ghienne, J.-F. & Deynoux, M. 1998. Large-scale channel fill structures in Late Ordovician glacial deposits in Mauritania, western Sahara. Sedimentary Geology 119 (1–2), 141–59.CrossRefGoogle Scholar
Ghienne, J.-F., Deynoux, M., Manatschal, G. & Rubino, J.-L. 2003. Palaeovalleys and fault-controlled depocentres in the Late-Ordovician glacial record of the Murzuq Basin (central Libya) [Paléovallées et dépocentres sur failles dans les séries glaciaires fini-ordoviciennes du bassin de Murzuq (Libye centrale)]. Comptes Rendus, Geoscience 335 (15), 1091–1100.CrossRefGoogle Scholar
Ghienne, J.-F., Le Heron, D. P., Moreau, J. & Deynoux, M. 2007. The Late Ordovician glacial sedimentary system of the West Gondwana platform. In Glacial Sedimentary Environments: Processes and Products (eds Hambrey, M. J., Cristofferson, P., Glasser, N., Hubbard, B. & Siegert, M.), pp. 295–319. International Association of Sedimentologists, Special Publication no. 39.CrossRefGoogle Scholar
Gundobin, V. N. 1985. Geological Map of Libya, Sheet NH-33 (Qararat al Marar Sheet). Industrial Research Centre, Tripoli, Libya.Google Scholar
Hirst, J. P. P., Benbakir, A., Payne, D. F. & Westlake, I. R. 2002. Tunnel Valleys and Density Flow Processes in the upper Ordovician glacial succession, Illizi Basin, Algeria: influence on reservoir quality. Journal of Petroleum Geology 25, 297–324.CrossRefGoogle Scholar
Huuse, M. & Lykke-Andersen, H. 2000. Overdeepened Quaternary valleys in the eastern Danish North Sea: morphology and origin. Quaternary Science Reviews 19, 1233–53.CrossRefGoogle Scholar
Jacqué, M. 1962. Reconnaissance Géologique du Fezzan Oriental. Notes et Mémoires du Compagnie Française des Pétroles (TOTAL). Paris, 5–43.Google Scholar
Klein, G. D. 1970. Depositional and dispersal dynamics of intertidal sand bars. Journal of Sedimentary Research 40, 1095–1127.Google Scholar
Le Heron, D. P. & Craig, J. 2008. First-order reconstructions of a Late Ordovician Saharan Ice Sheet. Journal of the Geological Society, London 165, 19–30.CrossRefGoogle Scholar
Le Heron, D. P., Craig, J., Sutcliffe, O. E. & Whittington, R. 2006. Glaciogenic Reservoir Heterogeneity: an example from the Late Ordovician of the Murzuq Basin, SW Libya. Marine and Petroleum Geology 23, 655–77.CrossRefGoogle Scholar
Le Heron, D., Sutcliffe, O., Bourgig, K., Craig, J., Visentin, C. & Whittington, R. 2004. Sedimentary Architecture of Upper Ordovician Tunnel Valleys, Gargaf Arch, Libya: Implications for the Genesis of a Hydrocarbon Reservoir. GeoArabia 9, 137–60.CrossRefGoogle Scholar
Le Heron, D. P., Sutcliffe, O. E., Whittington, R. J. & Craig, J. 2005. The origins of glacially related soft-sediment deformation structures in Upper Ordovician glaciogenic rocks: implication for ice sheet dynamics. Palaeogeography, Palaeoclimatology, Palaeoecology 218, 75–103.CrossRefGoogle Scholar
Lonergan, L., Maidment, S. C. R. & Collier, J. S. 2006. Pleistocene subglacial tunnel valleys in the central North Sea basin: 3-D morphology and evolution. Journal of Quaternary Science 21, 891–903.CrossRefGoogle Scholar
Lüning, S., Craig, J., Loydell, D. K., Storch, P. & Fitches, B. 2000. Lower Silurian “hot shales” in Northern Africa and Arabia: regional distribution and depositional model. Earth Science Reviews 49, 121–200.CrossRefGoogle Scholar
Moreau, J., Degermann, L., Ghienne, J. F. & Rubino, J. L. 2007. Large-scale physiography of the Murzuq Basin shelf during Hirnantian ice-sheet final retreat and Silurian transgression: outcrops and seismic interpretations. EAGE, 3rd North Africa/Mediterranean Petroleum & Geosciences Conference and Exhibition, Tripoli 2007.Google Scholar
Moreau, J., Ghienne, J.-F., Le Heron, D. P., Deynoux, M. & Rubino, J.-L. 2005. A 440 million year old ice stream in North Africa. Geology 33, 753–6.CrossRefGoogle Scholar
Ottesen, D., Dowdeswell, J. A., Rise, L., Rokoengen, K. & Henriksen, S. 2002. Large-scale morphological evidence for past ice-stream flow on the mid-Norwegian continental margin. In Glacier-influenced sedimentation on High-Latitude Continental Margins (eds Dowdeswell, J. A. & O'Cofaigh, C.), pp. 245–58. Geological Society of London, Special Publication no. 203.Google Scholar
Pařízek, A., Klen, L. & Rohlich, X. 1984. Geological Map of Libya, Sheet NG33–1 (Idri Sheet). Industrial Research Centre, Tripoli, Libya.Google Scholar
Patterson, C. J. 1994. Tunnel-valley fans of the St. Croix moraine, east-central Minnesota, USA. In Formation and Deformation of Glacial Deposits (eds Warren, W. P. & Croot, D. G.), pp. 69–87. Rotterdam: Balkema.Google Scholar
Powell, J. H., Basim Khalil, M. & Masri, M. 1994. Late Ordovician–Early Silurian glaciofluvial deposits preserved in palaeovalleys in South Jordan. Sedimentary Geology 89, 303–14.CrossRefGoogle Scholar
Rafaelsen, K., Andreassen, L., Kuilman, W., Lebesbye, E., Hogstad, K. & Midtbo, M. 2002. Geomorphology of buried glacigenic horizons in the Barents Sea from three-dimensional seismic data. In Glacier-influenced sedimentation on High-Latitude Continental Margins (eds Dowdeswell, J. A. & O'Cofaigh, C.), pp. 259–76. Geological Society of London, Special Publication no. 203.Google Scholar
Ramos, E., Marzo, M., de Gibert, J., Tawengi, K. S., Khoja, K. A. & Bolatti, N. D. 2006. Stratigraphy and sedimentology of the Middle Ordovician Hawaz Formation (Murzuq Basin, Libya). AAPG Bulletin 90, 1309–36.CrossRefGoogle Scholar
Smart, J. 2000. Seismic expressions of depositional processes in the upper Ordovician succession of the Murzuq Basin, SW Libya. In Geological exploration in Murzuq Basin (eds Sola, M. & Worsley, D.), pp. 397–415. Amsterdam: Elsevier.CrossRefGoogle Scholar
Subcommission on Ordovician Stratigraphy. 2008. Ordovician News 25, 63 pp.Google Scholar
Sutcliffe, O. E., Dowdeswell, J. A., Whittington, R. J., Theron, J. N. & Craig, J. 2000. Calibrating the Late Ordovician glaciation and mass extinction by the eccentricity cycles of Earth's orbit. Geology 28, 967–70.2.0.CO;2>CrossRefGoogle Scholar
Sutcliffe, O. E., Harper, D. A. T., Aït Salem, A., Whittington, R. J. & Craig, J. 2001. The development of an atypical Hirnantia brachiopod Fauna and the onset of glaciation in the Late Ordovician of Gondwana. Transactions of the Royal Society of Edinburgh, Earth Sciences 92, 1–14.CrossRefGoogle Scholar
Tod, S., Taylor, B., Johnston, R. & Allen, T. 2007. Fracture prediction from wide-azimuth land seismic data in SE Algeria. The Leading Edge 26 (9), 1154–60.CrossRefGoogle Scholar
Turner, B. R., Mahklouf, I. M. & Armstrong, H. A. 2005. Late Ordovician (Ashgillian) glacial deposits in southern Jordan. Sedimentary Geology 181, 73–91.CrossRefGoogle Scholar
Vaslet, D. 1990. Upper Ordovician glacial deposits in Saudi Arabia. Episodes 13, 147–61.CrossRefGoogle Scholar
Wingfield, R. 1990. The origin of major incisions within the Pleistocene deposits of the North Sea. Marine Geology 91 (1–2), 31–52.CrossRefGoogle Scholar