Each year, AAPG’s Petroleum Structure and Geomechanics Division recognizes what the membership considers the best recent and seminal publications in the field.
This year’s Best Seminal Publication award recognizes Tod Harding and Jim Lowell for their 1979 paper, “Structural styles, their plate-tectonic habitats, and hydrocarbon traps in petroleum provinces,” published in the AAPG Bulletin 63.
Division Chair Bob Krantz praised the work as “truly foundational.”
“To my knowledge, nobody had published anything like their core concept: relating typical geologic structures and hydrocarbon traps to recognizable structural systems, and then to their plate tectonic settings,” Krantz said.
He said the framework presented “has been one of the root concepts in how we teach and train and execute petroleum exploration. For me, most recently, I taught a module in a local college petroleum geology course earlier this year, and used the very same framework of structural styles related to geologic and plate tectonic contexts.”
The publication arrived as the plate tectonic revolution of the 1960s was becoming more widely accepted and applied in the mid-‘70s, he explained.
“During the same time period, Harding and Lowell, both at Exxon, compiled their experience and insights to how petroleum exploration geology could be aligned with the new paradigm, and how this would in turn guide and improve future exploration,” Krantz added.
Impact on the Science
He said the impact of the Harding and Lowe paper was “immediate and significant, given how most geologists, including some skeptics, felt strongly about such a broad change in the science.”
Krantz named two ways in which the paper was groundbreaking:
“First, while some explorationists were comfortable with the idea of seeing characteristic geologic structures and traps together, they thought mostly in geographic contexts, like the Alps or Wyoming or the Gulf Coast. Harding and Lowell reframed these assemblages of structures (and traps) into a more conceptual framework of geologic habitats that could exist in multiple locations around the globe.
“Second, they used the new emerging global plate tectonic paradigm to explain (and predict) the distribution of these habitats, and the types of structures and traps expected. This meant that explorationists could apply experience in a type of habitat to new basins,” he said.
According to the award citation written by Rick Groshong and Jim Granath, at the time, “There was almost nothing published about the connection between petroleum-related structural styles, basin architecture and plate tectonics.”
“If you consulted the textbooks of the day you would probably find a chapter on folds and another on faults, the significance of which only later were tied to each other. Structural styles were considered to be region-specific, so there would be a chapter or two on different provinces, like the Alps or the Canadian Rockies. But you would find very little if anything on the structure of continental shelves or topics like the link between rifting and ocean basins. You would not find much unified thought, and surely very little information about specific structural styles that would help in answering those practical exploration questions.
“A great deal of practical interpretation is done by comparing the structure of interest to analogs, but the problem is to choose the right analog. The Harding and Lowell paper began to fill those gaps. It introduced a practical and region-independent framework for categorizing structural styles,” the citation said.
The citation continued: “The classification quickly became, and remains, the most widely used framework for interpreting oilfield structures. The paper includes excellent examples of the individual structural styles in map view and cross section. The examples are the starting point for filling in the three-dimensional geometries of structures under study. The connections made in the paper between this structural framework and plate tectonics provided a new approach to answering the questions about where to explore and what to expect when you got there.”
The Harding and Lowell paper “laid the groundwork for the subsequent ‘mini-revolutions’ that have and continue to afford us a deeper understanding of each of the styles, the citation said.
“(The paper) was a big help at the time and provides an essential background for many things we not only do today but also will continue to do into the future,” the citation concluded.
What’s Old is New
Forty years after the original publication, Harding still has a drive to contribute to his field.
“When notified of this year’s award, Tod Harding immediately replied with how he wants to update the original paper. In correspondence over the past month, I have learned how his passion for geology, and for contributing to exploration geology, still burns as intensely as ever – at age 90,” Krantz said.
“(Harding) feels that the 1979 publication omits a significant family of structures that fit in the concept of tectonic inversion, where older faults get reactivated during younger events,” Krantz said.
“In a sense, inversion is not ‘news,’ and has been widely recognized since 1979, but it was fun to see how Tod wants his original catalog to be complete,”Krantz said.
Harding outlined some key additions and supplied some hand sketches of his ideas, which Krantz redrafted for presentation at the Division’s award session on May 21.
“Tod Harding attended with his wife and daughter, and stole the show. Many Division members know him by reputation and were excited to meet him in person,” Krantz said.
The Petroleum Structure and Geomechanics Division for the past four years has recognized the best recent paper in the field along with a seminal publication.
The 2019 Best Recent Publication award recognized authors Randy Marrett of the University of Texas at Austin, Julie Gale of the Bureau of Economic Geology at UT, Leonel Gomez of ExxonMobil, and Steve Laubach of the Bureau of Economic Geology at UT.
This paper provided both the theory and tools, including public access software, to analyze systems of fractures, especially in their 3-D distributions, according to Division Chair Bob Krantz.
The work published in the paper comes in part from the doctoral research that Gomez did under Marrett’s supervision at UT.