Imagine the Mediterranean Sea drying out.
Imagine the late Permian, as the Earth warmed and dried, and much of life faced extinction.
Now put the two together, and you have the basis of an analog proposed by AAPG member John Pigott, associate professor at the University of Oklahoma, and his fellow researchers.
This concept will be examined in the presentation “The Messinian Mediterranean Crisis: A Model for the Permian Delaware Basin?” at the upcoming AAPG International Conference and Exhibition in Istanbul, Turkey.
EXPLORER: What are the main findings of this research?
PIGOTT: Both the late Miocene Mediterranean and the late Permian Delaware intracontinental seas became isolated when their major inlets to the world oceans pulsed in their restriction and eventually closed (the ancestral Strait of Gibraltar and the Hovie Channel, respectively).
As a result, with restriction and eventual cut-off, both basins became increasingly anoxic and saline, with organic rich sediments culminating in extensive evaporates (the Messinian and Ochoan Castille evaporates, respectively).
The two basins are separated both in time and space and they also differ in principal depositional environments: the dominantly clastic Mediterranean versus the dominantly carbonate Delaware basin.
Two questions are posed:
Are the parallels between the two basins in terms of associated tectonics, global climate change, and eustatic changes in sea level coincidental or process-related?
Can their comparative anatomy of tectonics and sedimentary processes-responses provide reciprocating insight into their hydrocarbon exploration, and potentially to similarly restricted evaporite basins elsewhere?
EXPLORER: What are the key scientific elements involved?
PIGOTT: When expressed laterally instead of vertically, the classic “Usiglio” sequence of evaporite mineral deposition (calcite -> gypsum -> anhydrite -> halite -> sylvite, and such) as basins become more and more restricted tends to generally point away from inlets of ocean water replacement.
Both the Messinian and Delaware basin salts exhibit a general west-to-east Usiglio lateral trend, suggesting basin restriction, evaporation and ocean influx from the west. When there exists a massive one-way transfer in water mass – for example, evaporation in a peripheral basin cut-off to the world ocean – the basin’s sea level curve is antithetic to that of the parent world ocean.
This change is documented in the borehole-constrained seismic stratigraphy of the Messinian Nile Delta, which shows Mediterranean relative sea level fall during a time of global sea level rise.
Concomitantly, the global eustatic curve listens to peripheral basin water volume change, for example, the dramatic and almost globally pervasive Messinian unconformity observed in offshore seismic, which corresponds to the Zanclean Flood and transfer of massive quantities of ocean water back into the Mediterranean.
Consequently, can the oscillations observed in the global eustatic sea level curve be used as a guide to prediction of basin restriction and anoxia within these two basins?
EXPLORER: How does that affect source rock in these basins?
PIGOTT: It is not just the paradigm of the maximum flooding surface that provides the highest organic carbon content, but bathymetrically controlled pockets of anoxia, which can provide a heterogeneous basin distribution of preserved organic source-rock richness.
As salt conductivities are high, venting of heat allows sub-salt oil windows to be deeper than in adjacent non-salt regions of similar heat flows.
While these two evaporate basins differ dramatically in their ending, both share common themes of process-response, shared themes that can potentially impact their ongoing hydrocarbon exploration.
It should be said that each basin in the world is different. However, there are reoccurring common themes in geological process and response that directly affect the evolution of petroleum systems.
EXPLORER: How was your basic concept developed?
PIGOTT: In my day job, I teach and conduct research in basin analysis and seismic stratigraphy at the University of Oklahoma (OU). My students challenge me to find new paradigms. In my off times, I consult worldwide for companies and governments and instruct for the industry through PetroSkills.
My clients challenge me to find paradigms that help them find oil and gas. So looking for analogs within and among basins is a constant attempt at model verification. But as I do not work in a vacuum, this particular idea grew from the critical joint collaboration of my three co-authors (all AAPG members):
♦ Michael T. Williams (now at XTO), who spent hundreds of hours poring over logs in the Midland Library and setting up the three-dimensional basin model.
♦ Kulwadee L. Pigott (my wife and co-instructor at OU), who assisted with geochemical constraints upon the thermal histories and migration pathways.
♦ Mohamed Abdel Fattah (post-doc at OU) who works with me on Eastern Mediterranean seismic stratigraphy.
Intrigued by the mysterious location of the missing Hovie Channel postulated by P.B. King in 1942, we noted evaporite mineral changes were more west-to-east than south-to-north. And in the Mediterranean, we noted a similar trend. So this was the nucleus of the idea of comparing the basins.
EXPLORER: What other implications does this have for oil and gas exploration?
PIGOTT: While exploration on the periphery of the Mediterranean continues to focus upon the effects of the Messinian crisis upon fluvial systems within incised valleys sealed by transgressive fills, are there clastic analogs along the Delaware shelf edge?
The Mediterranean has a lumpy bottom with anoxic sub-basins, which focused organic deposition and preservation during restriction pulses. Might a similar spatial and temporal heterogeneity in source rock richness be exhibited by the sub-basins in the poorly seismically imaged Delaware Basin basement floor?
Post-Messinian tectonics have led to discoveries in the Eastern Mediterranean – the Levantine Basin by Noble Energy, for example. Could deciphering the strain history and structuring of the post-Permian Delaware similarly lead to new exploration ideas, especially in the East?
Can the Delaware – and for that matter, the Permian Basin nonconventional play concepts – be used on the onshore basins peripheral to the Mediterranean (Western Desert of Egypt, for example)?
Could there be high-energy prospective reservoir sands associated with the Strait of Gibraltar Messinian Zanclean Flood and Hovie Channel influxes during Permian global sea level oscillations?
Do other Permian evaporite basins of the world have similarities to these two?
EXPLORER: The Messinian salinity event has been well studied and has generated a lot of theories. Is this approach – and analog – a new concept for the Delaware Basin?
PIGOTT: It is such an obvious comparison, it is difficult to imagine that such an idea has not been thought of and tested before. In any case, I do think asking the question is appropriate.
EXPLORER: These events are far apart in time. Are the similarities really that strong?
PIGOTT: There are definitely differences. But the time of the Permian and its demise is a really strange time in the Earth’s past, climatically, biologically, geographically and, likely, atmospherically.
Any insight the more youthful and thus better stratigraphically resolvable and preserved Messinnian can provide into not just the Delaware Basin, but also into the numerous other Permian evaporate basins of the world, would be most helpful not just in our general understanding of the Permian, but to its hydrocarbon exploration and exploitation.
Indeed, the Permian Basin in the United States is by no means a small exploration province, where some have projected its present production – at about 1.3 million barrels – to double in the near future with increased unconventional exploration, and rival that of Kuwait.
EXPLORER: What work remains to be done in this Messinian Mediterranean/Delaware Basin comparison?
PIGOTT: Much. At the moment I, my wife Kulwadee, and my graduate students and post-docs are working on refining the Delaware sequence stratigraphy (AAPG member Yuqi Zhou); Delaware and Midland Basin modeling (AAPG member Michael Williams, Esra Yalcin and Katie Garrett); Permian Basin carbonate seismic stratigraphy (AAPG member Sam Martin); Permian-modern comparative Diagenesis (AAPG member Emma Giddens); and Mediterranean Seismic Stratigraphy (Mohamed Abdel-Fatah and Jerry Zhai).
We are hopeful these parts may fit into the puzzle and provide additional verification or refutation of our hypotheses concerning parallels between the two basins.
EXPLORER: Is there anything here we should take away with us in thinking about glaciation, climate and rainfall today?
PIGOTT: The global climate is complex, a result of more feed-back mechanisms than we as scientists can at this moment accurately predict for the short-term.
However, with respect to the long term, what we as geoscientists can do is attempt to decipher the Earth’s past climates and thus provide from retrospection a model for forecasting future earth climates.
EXPLORER: Just out of curiosity, do you accept the very fast Zanclean flooding hypothesis?
PIGOTT: The Zanclean Flood, or Zanclean Deluge, has been proposed to be the event that refilled the Mediterranean 5.3 million years ago at an enormous rate in what some workers have estimated to be months to a decade in time.
To explain the massive inlet deposits viewed at the Gibraltar inlet, the Messinian evaporites, one must subscribe to large volumes of water being transferred.
From our bore-hole constrained seismic stratigraphy on the Nile delta what we do see is indeed an enormous transgressive (flooding) event, but at the moment we lack the stratigraphic resolution to resolve with certainty the number of years responsible.
Certainly, the flooding event was both immense and fantastic, in whatever amount of time it took.
EXPLORER: You’ve recently returned from Iceland. What were you doing, and what did you think about the country?
PIGOTT: Indeed, to put it philosophically: It is the ad posteriori that amplifies and augments the a priori in the geosciences. That is, the more we see and touch through experience, the greater the cerebral library introduced in the classroom can become if we tangibly put not just our minds but our hands around it.
Iceland is but another page in my geoscience cerebral book. In very few places in the world can one look at what happens when a hot spot is placed underneath a spreading center in a high latitude.
Iceland is a fantastic collage of physical and biological scenery – active and historical volcanic activity, strange igneous associations, glaciers, thermal springs, geysers, fantastic high energy storm beach processes, waterfalls, icebergs, moss-covered rift valleys with submerged canyons in which you can scuba dive, whales, seals, horses introduced a thousand years ago, and the mighty puffins.