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Explorer Article

Industry and academia are teaming up to pump up activity in the Mississippian of the Midcontinent United States.


This article addresses the controls exerted by sedimentologic and diagenetic factors on the preservation and modification of pore-network characteristics (porosity, pore types, sizes, shapes, and distribution) of carbonates belonging to the Bolognano Formation. This formation, exposed at the Majella Mountain, Italy, is composed of Oligocene–Miocene carbonates deposited in middle- to outer-ramp settings. The carbonates consist of (1) grainstones predominantly composed of either larger benthic foraminifera, especially Lepidocyclina, or bryozoans; (2) grainstones to packstones with abundant echinoid plates and spines; and (3) marly wackestones to mudstones with planktonic foraminifera.

The results of this field- and laboratory-based study are consistent with skeletal grain assemblages, grain sizes, sorting, and shapes, all representing the sedimentologic factors responsible for high values of connected primary macroporosity in grainstones deposited on the high-energy, middle to proximal outer ramp. Cementation, responsible for porosity reduction and overall macropore shape and distribution in grainstones to packstones deposited on the intermediate outer ramp, was mainly dependent on the following factors: (1) amount of echinoid plates and spines, (2) grain size, (3) grain sorting and shapes, and (4) clay amount. Differently, in the wackestones to mudstones, laid down on the low-energy, distal outer ramp, matrix is the key sedimentologic factor responsible for low values of scattered macroporosity and dominance of microporosity. The aforementioned results may be useful to improve the prediction of reservoir quality by means of mapping, simulating, and assessing individual carbonate facies with peculiar pore-network characteristics.


“My concept of reservoirs has completely changed.”


In their recent discussion of the recognition of late burial dissolution of carbonates, Ehrenberg et al. (2012) use our article (Beavington-Penney et al., 2008) as an example of a study that mistakes late burial (mesogenetic) porosity for pores that formed much earlier in the diagenetic sequence. Commenting on our study of reservoir quality variation in Eocene nummulitic limestones, Ehrenberg et al. (2012, p. 229) note that “hellipthe pores in the photomicrographs shown [our figure 8]hellip appear to be combinations of primary intrachamber (nummulite [sic]) and intergranular macropores, in some cases augmented by molds of possible eogenetic origin.” However, they did not mention the evidence we present (our figure 8G) of dissolution immediately below a stylolite and along apparently stylolite-related fractures. Ehrenberg et al. perhaps feel that one photomicrograph is not unambiguous evidence supporting our conclusion that interparticle vuggy porosity developed in micritic matrix during late burial diagenesis, but we feel that, as part of a balanced discussion, it would at least have been reasonable to acknowledge that we present direct evidence of dissolution that apparently postdates chemical compaction, before dismissing our model.

It is not an original observation that late burial corrosion is commonly hard to identify and prove (e.g., see Mazzullo and Harris, 1992), and it is reasonable that models invoking such processes should be open to challenge. However, it is disappointing that neither authors nor reviewers noticed that the criticism of our article neglected to mention a key piece of evidence in favor of a mesogenetic model. I do not attempt here to question the validity of Ehrenberg et al.'s argument that the identification of such late-stage porosity is commonly mistaken (or to comment on the validity of their criticism of other published articles) but instead to point out that this argument would be better served by an accurate portrayal of the evidence presented in the case studies they choose to criticize.


The Sierra Diablo Mountains of west Texas contain world-class exposures of Lower Permian (Leonardian) platform carbonates. As such, these outcrops offer key insights into the products of carbonate deposition in the transitional icehouse to greenhouse setting of the early to middle Permian that are available in few other places. They also afford an excellent basis for examining how styles of facies and sequence development vary between inner and outer platform settings.

We collected detailed data on the facies composition and architecture of lower Leonardian high-frequency cycles and sequences from outcrops that provide more than 2 mi (3 km) of continuous exposure. We used these data to define facies stacking patterns along depositional dip across the platform in both low- and high-accommodation settings and to document how these patterns vary systematically among and within sequences.

Like icehouse and waning icehouse successions elsewhere, Leonardian platform deposits are highly cyclic; cycles dominantly comprise aggradational upward-shallowing facies successions that vary according to accommodation setting. Cycles stack into longer duration high-frequency sequences (HFSs) that exhibit systematic variations in facies and cycle architectures. Unlike cycles, HFSs can comprise symmetrical upward-shallowing or upward-deepening facies stacks. High-frequency sequences are not readily definable from one-dimensional stratigraphic sections but require dip-parallel two-dimensional sections and, in most cases, HFS boundaries are best defined in middle platform settings where facies contrast and offset are greatest. These studies demonstrate that HFSs are the dominant architectural element in many platform systems. As such, the lessons learned from these remarkable outcrops provide a sound basis for understanding and modeling carbonate facies architecture in other carbonate-platform successions, especially those of the middle to upper Permian.

Although the linkages among surface sediments, geomorphic forms, and hydrodynamics in Holocene ooid tidal sand shoals have been evaluated recently, how these factors are reflected in the geomorphic evolution and stratigraphic record of shoals is less constrained. Yet, such understanding is essential to developing meaningful predictive conceptual models of three-dimensional architecture of ancient reservoir analogs. Integrating remote-sensing imagery, high-frequency seismic data, and core characterization from Lily Bank, a modern tidally dominated Bahamian ooid shoal in which sedimentologic processes are well documented, reveals the stratigraphic record of geomorphic change. An irregular, gently dipping rocky surface (interpreted as the top Pleistocene) with no pronounced topographic high underlies the Holocene oolitic succession. A 6-m (20-ft)–thick poorly sorted, gravelly muddy sand with few ooids overlies this basal surface. This lower interval is overlain by sand with an upward increase in proportion of ooids, sorting, and grain size. The uppermost unit, present only under active bar forms, is well-sorted oolitic medium sand with accretionary foresets. Sediments vary stratigraphically and geomorphically; the lower unit is finer and less well sorted than the upper units, and in the oolitic upper unit, sediment size and sorting on bar crests are distinct from bar flanks. Collectively, these results suggest that a marked antecedent bump is not necessary for occurrence of ooid shoals and that the stratigraphic record of analogous ooid shoal systems may preserve clues of geomorphic position, as well as geobody size and orientation.

Select lacustrine and marine depositional settings show a spectrum of styles of carbonate deposition and illustrate the types of carbonates, with an emphasis on microbialites and tufa, to be expected in early rift settings. Early rift lake examples examined in this review article are all from East Africa: Lakes Turkana, Bogoria, Natron and Magadi, Manyara, and Tanganyika. Other lake examples include four from the western United States (Great Salt Lake and high lake level Lake Bonneville, Mono Lake and high lake level Russell Lake, Pyramid Lake and high lake level Lake Lahontan, and Searles Lake) and two from Australia (Lakes Clifton and Thetis). Marine basin examples are the Hamelin Pool part of Shark Bay from Australia (marginal marine) and the Red Sea (marine rift).

Landsat images and digital elevation models for each example are used to delineate present and past lake-basin margins based on published lake-level elevations, and for some examples, the shorelines representing different lake levels can be compared to evaluate how changes in size, shape, and lake configuration might have impacted carbonate development. The early rift lakes show a range of characteristics to be expected in lacustrine settings during the earliest stages of continental extension and rifting, whereas the Red Sea shows well advanced rifting with marine incursion and reef–skeletal sand development. Collectively, the lacustrine examples show a wide range of sizes, with several of them being large enough that they could produce carbonate deposits of potential economic interest. Three of the areas—Great Salt Lake and high lake level Lake Bonneville, Pyramid Lake and high lake level Lake Lahontan, and the Red Sea—are exceedingly complex in that they illustrate a large degree of potential depositional facies heterogeneity because of their size, irregular pattern, and connectivity of subbasins within the overall basin outline.


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.


Added to the "first-time-ever” list was the announcing of paper and poster awards at the end of the event.

Explorer Emphasis Article

Closest of trends: Geoscientists experienced a huge “aha!” moment that started with the realization that Pennsylvania’s Marcellus Shale and Texas’ Eagle Ford Shale have a lot in common.

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In-Person Training
Houston Texas United States 10 November, 2014 11 November, 2014 10487
Houston, Texas, United States
10-11 November 2014

This course summarizes the major advances and current controversies in dolomite research.

Houston Texas United States 12 November, 2014 12 November, 2014 10570
Houston, Texas, United States
12 November 2014

This course is designed to present the concepts of sedimentary geochemistry and biogeochemistry, along with the framework to interpret elemental and mineralogical records in such organic rich mudstone sequences.

Houston Texas United States 13 November, 2014 13 November, 2014 10572
Houston, Texas, United States
13 November 2014

The course begins with a short review of the basic principles of carbonate well logging and goes on to detail the different carbonate pore types and the logging methods used to differentiate the various pore types and to determine their hydrocarbon productive potential.

Oklahoma City Oklahoma United States 19 February, 2015 19 February, 2015 11378
Oklahoma City, Oklahoma, United States
19 February 2015

This year’s Mississippian Lime Forum unleashes science, technology, and experience to solve persistent puzzles, and dramatically improve economics. Consider 2015 a breakthrough year as new, sometimes controversial new techniques and technologies are being implemented for the first time.

14 February, 3000 14 February, 3000 7812
14 February, 3000 14 February, 3000 7815
14 February, 3000 14 February, 3000 7813
14 February, 3000 14 February, 3000 7816
Online Training
21 February, 2013 21 February, 2013 1495
21 February 2013

The course will review core data, petrophysical comparisons, rock physics modeling (including pseudo logs and mechanical properties).

01 January, 2013 01 January, 9999 1459
1 January 2013 - 1 January 9999

There are more approximately 1,000 oil and gas fields in the world that have been classified as "giant," containing more than 500 million barrels of recoverable oil and /or 3 trillion cubic feet of gas.

30 August, 2012 30 August, 2012 1489
30 August 2012

The entire Middle Pennsylvanian–to–top Precambrian basement (500 m) interval was cored in early 2011 in the BEREXCO Wellington KGS #1-32 well in Wellington Field, Sumner County, KS.

24 October, 2013 24 October, 2013 1499
24 October 2013

This e-symposium will be introducing signal processing techniques as a means to maximize extracting geomechanical data from petrophysical logs.

07 June, 2012 07 June, 2012 1488
7 June 2012

Unger Field, discovered in1955, has produced 8.6 million barrels of oil from a thinly (several ft) bedded, locally cherty dolomite containing vuggy and intercrystalline porosity.

10 November, 2011 10 November, 2011 1481
10 November 2011

This work investigates how heterogeneity can be defined and how we can quantify this term by describing a range of statistical heterogeneity (e.g. coefficient of variation and the Lorenz coefficient).

28 April, 2011 28 April, 2011 1471
28 April 2011

The Niobrara Petroleum System of the U.S. Rocky Mountain Region is a major tight petroleum resource play.

11 November, 2010 11 November, 2010 1465
11 November 2010

This e-symposium is ideal for geologists, geophysicists, engineers and other geoscientists who are involved in gas shale exploration and production.

14 February, 3000 14 February, 3000 7817
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