Two-Way Street: Making a Connection That Counts

Here in Oklahoma, the month of July delivers the beginning of summer, kids out of school and a unique blend of oppressive heat and sweltering humidity that makes you feel like you're in a slow-cooker.

At headquarters it's the beginning of a new year. On July 1 a fresh Executive Committee led by President Randi Martinsen took the reins, approved a budget for the new fiscal year and is beginning its work to lead the Association.

Veteran EC members Secretary Richard Ball, Vice President-Regions John Kaldi and Editor Mike Sweet are joined by President-Elect John Hogg, Treasurer Jim Tucker and Vice President-Sections Steve Brachman in this endeavor.

These are your leaders, and I encourage you to reach out and communicate with them during the coming year.

I also want to take this opportunity to thank past president Lee Krystinik for his leadership of the Association and Executive Committee, and most emphatically for his wise counsel to me over the past two years that he's served on the Executive Committee.

As past president, Lee's work isn't done yet. He now rides over to lead the Advisory Council further down the trail blazed by past president Ted Beaumont.

(You'll note the riding-themed metaphors I'm using in this column. Having incoming and outgoing presidents who are both accomplished equestrians is forcing me to learn a new vocabulary.)

When I first began to work for AAPG, back in Washington, D.C., in 2006, one of the first people I met was Deborah Sacrey, our out-going treasurer who has been involved in our policy work since the very beginning. We've worked closely over the years, and the perspective and advice she's given me both at GEO-DC and as executive director have helped me do my job immeasurably better.

Thankfully, she's still only a phone call away.

I've known Tom Ewing, who departs as vice president-Sections, almost as long as I've known Deborah. And Tom brought a wonderful balance of thoughtfulness, perceptiveness and practicality to a host of EC discussions over the past two years.

Even into the final weeks of his term he was providing me counsel on matters related to the Sections and affiliated societies.


Having the opportunity to work directly with our EC members to grow AAPG is one of the perks of my job. And it's important to recognize that they are volunteers.

Volunteerism is at the heart of AAPG and permeates our organization. It includes those who volunteer to help us advance science by giving a talk or writing a journal article, those who work on committees to build specific programs or services, and those who serve in leadership and governance roles.

When you get involved with AAPG you're serving other members and the profession. This engagement also builds your professional network and can help you develop specific skill sets, particularly interpersonal skills - after all, in a volunteer organization you don't dictate, you can only persuade.

Yes, volunteering is about "giving back." But I'd argue it's much more than that.

It is, in fact, an investment in yourself - both as a person and as a professional. And that's what being a member of a professional organization is about - helping you advance and succeed.


It's summertime here in Oklahoma. And many of us in this part of the world will be taking time this month with family and friends to vacation, to relax and recharge both physically and emotionally.

As you climb that mountain trail, cast a fly along the riverbank, listen to the waves break on the shore or simply sit on your back porch at dusk listening to the crickets chirping in the grass, take a few minutes to reflect on your career and professional life.

Where are you and where are you going?

Can you describe what it would look like to take your career to the next level?

What are the skills or contacts that you need to get there?

Is there an AAPG program or committee or group that you could get involved with to gain those skills or contacts?

If so, consider getting plugged in.

And if you don't see a program that will help you, then I’d ask you to send me an email through the website. Let me know what kind of program you'e looking for, what you believe you need to be successful, and let's talk about it. Maybe we can build it together.

This is your year to take the reins, saddle up, and steer your career into an even brighter future.

Giddy up!

Comments (0)

 

Director's Corner

Director's Corner - David Curtiss

David Curtiss is an AAPG member and was named AAPG Executive Director in August 2011. He was previously Director of the AAPG GEO-DC Office in Washington D.C.

The Director's Corner covers Association news and industry events from the worldview perspective of the AAPG Executive Director.

View column archives

See Also: Bulletin Article

We reviewed the tectonostratigraphic evolution of the Jurassic–Cenozoic collision between the North American and the Caribbean plate using more than 30,000 km (18,641 mi) of regional two-dimensional (2-D) academic seismic lines and Deep Sea Drilling Project wells of Leg 77. The main objective is to perform one-dimensional subsidence analysis and 2-D flexural modeling to better understand how the Caribbean collision may have controlled the stratigraphic evolution of the offshore Cuba region.

Five main tectonic phases previously proposed were recognized: (1) Late Triassic–Jurassic rifting between South and North America that led to the formation of the proto-Caribbean plate; this event is interpreted as half grabens controlled by fault family 1 as the east-northeast–south-southwest–striking faults; (2) Middle–Late Jurassic anticlockwise rotation of the Yucatan block and formation of the Gulf of Mexico; this event resulted in north-northwest–south-southeast–striking faults of fault family 2 controlling half-graben structures; (3) Early Cretaceous passive margin development characterized by carbonate sedimentation; sedimentation was controlled by normal subsidence and eustatic changes, and because of high eustatic seas during the Late Cretaceous, the carbonate platform drowned; (4) Late Cretaceous–Paleogene collision between the Caribbean plate, resulting in the Cuban fold and thrust belt province, the foreland basin province, and the platform margin province; the platform margin province represents the submerged paleoforebulge, which was formed as a flexural response to the tectonic load of the Great Arc of the Caribbean during initial Late Cretaceous–Paleocene collision and foreland basin development that was subsequently submerged during the Eocene to the present water depths as the arc tectonic load reached the maximum collision; and (5) Late Cenozoic large deep-sea erosional features and constructional sediment drifts related to the formation of the Oligocene–Holocene Loop Current–Gulf Stream that flows from the northern Caribbean into the Straits of Florida and to the north Atlantic.

Desktop /Portals/0/PackFlashItemImages/WebReady/Subsidence-controls-on-foreland-basin.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3526 Bulletin Article
Transfer zones in rift basins are classified into convergent, divergent, and synthetic, based on the relative dip directions of adjacent faults within the transfer zone. Experimental models were constructed to determine the geometry, evolution, and fault patterns associated with each of these transfer zones. In addition, basement faults with initially approaching, laterally offset, and overlapping geometries were modeled. The models consisted of two layers, with stiff clay representing basement and soft clay representing the sedimentary cover. Laser scanning and three-dimensional surface modeling were used to determine the map geometry to compare the models with examples of natural structures. The experimental models showed many similarities with conceptual models but also showed more details and a few significant differences. Typically, divergent transfer zones are narrower than convergent transfer zones, for the same initial spacing between basement faults. The differences between the different initial fault configurations (approaching, laterally offset, or overlapping) are the degree of interaction of the secondary faults, the amount of overlap between the fault zones, and in some cases, the width of the transfer zone. The main faults propagate laterally and upward and curve in the direction of dip of the faults, so that the faults curve toward each other in convergent transfer zones, away from each other in divergent transfer zones, and in the same direction in synthetic transfer zones. A primary difference with schematic models is the significant component of extensional fault propagation folding (drape folding), accompanied by secondary faulting within the sedimentary cover, especially in the early stages of fault propagation. Therefore, all three types of transfer zones are characterized by significant folding and related variations in the shapes of structures. The transfer zones are marked by a progressive change in relief from the footwall to the hanging wall, resulting in a saddle-shaped geometry. The hanging walls of the faults are marked by a gentle flexure or rollover into the fault, with the amount of flexure increasing with fault throw away from the fault tip. The geometries and fault patterns of the experimental structures match some of the observations in natural structures and also provide predictive analogs for interpretation of surface and subsurface structures and the delineation of structural traps in rift basins.
Desktop /Portals/0/PackFlashItemImages/WebReady/Experimental-models-of-transfer-zones-in-rift.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3723 Bulletin Article
Jurassic deposition in the Maghrebian tethys was governed by eustasy and rifting. Two periods were delineated: (1) a carbonate shelf (Rhaetian–early Pliensbachian) and (2) a platform-basin complex (early Pliensbachian–Callovian). The carbonate shelf evolved in four stages, generating three sedimentary sequences, J1 to J3, separated by boundary sea level falls, drawdown, exposure, and local erosion. Sediment facies bear evidence of sea level rises and falls. Lateral changes in lithofacies indicate shoaling and deepening upward during the Sinemurian. A major pulse of rifting with an abrupt transition from carbonate shelf to pelagic basin environments of deposition marks the upper boundary of the lower Pliensbachian carbonate shelf deposits. This rifting episode with brittle fractures broke up the Rhaetian–early Pliensbachian carbonate shelf and has created a network of grabens, half grabens, horsts, and stacked ramps. Following this episode, a relative sea level rise led to pelagic sedimentation in the rift basins with local anoxic environments that also received debris shed from uplifted ramp crests. Another major episode spanning the whole early Pliensbachian–Bajocian is suggested by early brecciation, mass flows, slumps, olistolites, erosion, pinch-outs, and sedimentary prisms. A later increase in the rates of drifting marked a progress toward rift cessation during the Late Jurassic. These Jurassic carbonates with detrital deposits and black shales as the source rocks in northeastern Tunisia may define interesting petroleum plays (pinch-out flanking ramps, onlaps, and structurally upraised blocks sealed inside grabens). Source rock maturation and hydrocarbon migration began early in the Cretaceous and reached a maximum during the late Tortonian–Pliocene Atlassic orogeny.
Desktop /Portals/0/PackFlashItemImages/WebReady/a-transition-from-carbonate-shelf-to-pelagic.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3766 Bulletin Article

Increased rates of seismicity in tectonically quiescent regions like the midcontinent region of the United States have been hypothesized to be related to human activities such as oil and gas production and wastewater injection. It can be difficult to establish how human activities relate to earthquakes, particularly when local seismic networks are not available to provide a high-quality characterization of the seismic sequence in question.

Desktop /portals/0/images/bulletin/2015/09sep/Regional-detection-and-monitoring-of-injection2.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 22505 Bulletin Article
The geometries of clay smears produced in a series of direct shear experiments on composite blocks containing a clay-rich seal layer sandwiched between sandstone reservoir layers have been analyzed in detail. The geometries of the evolving shear zones and volume clay distributions are related back to the monitored hydraulic response, the deformation conditions, and the clay content and strength of the seal rock. The laboratory experiments were conducted under 4 to 24 MPa (580–3481 psi) fault normal effective stress, equivalent to burial depths spanning from less than approximately 0.8 to 4.2 km (0.5 to 2.6 mi) in a sedimentary basin. The sheared blocks were imaged using medical-type x-ray computed tomography (CT) imaging validated with optical photography of sawn blocks. The interpretation of CT scans was used to construct digital geomodels of clay smears and surrounding volumes from which quantitative information was obtained. The distribution patterns and thickness variations of the clay smears were found to vary considerably according to the level of stress applied during shear and to the brittleness of the seal layer. The stiffest seal layers with the lowest clay percentage formed the most segmented clay smears. Segmentation does not necessarily indicate that the fault seal was breached because wear products may maintain the seal between the individual smear segments as they form. In experiments with the seal layer formed of softer clays, a more uniform smear thickness is observed, but the average thickness of the clay smear tends to be lower than in stiffer clays. Fault drag and tapering of the seal layer are limited to a region close to the fault cutoffs. Therefore, the comparative decrease of sealing potential away from the cutoff zones differs from predictions of clay smear potential type models. Instead of showing a power-law decrease away from the cutoffs toward the midpoint of the shear zone, the clay smear thickness is either uniform, segmented, or undulating, reflecting the accumulated effects of kinematic processes other than drag. Increased normal stress improved fault sealing in the experiments mainly by increasing fault zone thickness, which led to more clay involvement in the fault zone per unit of source layer thickness. The average clay fraction of the fault zone conforms to the prediction of the shale gouge ratio (SGR) model because clay volume is essentially preserved during the deformation process. However, the hydraulic seal performance does not correlate to the clay fraction or SGR but does increase as the net clay volume in the fault zone increases. We introduce a scaled form of SGR called SSGR to account for increased clay involvement in the fault zone caused by higher stress and variable obliquity of the seal layer to the fault zone. The scaled SGR gives an improved correlation to seal performance in our samples compared to the other algorithms.
Desktop /Portals/0/PackFlashItemImages/WebReady/Three-dimensional-structure-of-experimentally-produced.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3722 Bulletin Article