Abstract A Holocene carbonate beach to eolian-dune sequence is a significant geomorphic feature along the Isla Cancun barrier island. The dunes are low, coalescing, parabolic dunes forming a ridge parallel to the present shoreline. The dunes comprise the “Bianca eolianite” and the slightly older “Cancun eolianite.” The Blanca eolianite is similar in age to the modern beach system. The more lithified Cancun eolianite, which forms excellent outcrop sections, contains three stratification types: 57% of the dune system is climbing translatent stratification, 36% is grainfall lamination, and 7% is sandflow cross-stratification. Biogenic structures in the Cancun and Blanca eolianites include animal burrows and rhizoliths. The general lateral transition between the modern beach system and the adjacent Blanca eolian dune system appears to have a fair-weather equilibrium profile with no abrupt break between the back beach and toe of dune. The quantity of coarse shell material and animal burrows decreases significantly into the dunes, where eolian processes dominate over marine processes. Sediment sorting and plant-root traces increase dramatically in the area where eolian processes become dominant. During strong storms and hurricanes, marine processes may reach well into the eolian realm, removing the beach sediment in front of dune deposits and allowing the swash or surf to erode the dunes directly. During rare, exceptionally severe hurricanes, the dune complex can be truncated, as is evident in the Cancun eolianite. This interaction between marine and eolian processes forms a time-transient boundary (interfingering) in the beach-dune systems. Marine-produced features that punctuate eolian deposits are: (1) dune-front conglomerates produced during dune-front erosion and (2) intradune marine storm deposits laid down during dune truncation.

Abstract In the deep sea, benthic macro-organisms leave few or no body fossils, owing to both calcite dissolution on the abyssal ocean floor and the predominance of soft-bodied organisms in abyssal communities. Deep-sea trace fossils provide geologists with virtually the only fossil evidence of the benthic macroinvertebrate community in ancient abyssal environments. In fact, their trace fossils often yield important ecologic and ethologic information, such as the relative importance of suspension feeders and deposit feeders in the bottom community, that body fossils may not provide even if present. Deep-sea sediments at all latitudes and water depths in the world's oceans today exhibit intense bioturbation caused by the burrowing activities of benthic organisms (Berger, Ekdale and Bryant, 1979; Ekdale and Berger, 1978; Scholle, Arthur and Ekdale, 1983; Ekdale, Muller and Novak, 1984. The relatively low depositional rates of pelagic material (generally less than 3 cm per thousand years) allow even a very low abundance of burrowers to mix the sediment so effectively that primary structures and stratification are not preserved. Thus, biogenic sedimentary structures and complex ichnofabrics are the general rule in pelagic ooze and clay; primary depositional structures are the exception. On the other hand, land-derived material in turbidites typically reaches deep-water settings in a rapid and spasmodic manner. These deposits generally are well-bedded and display a variety of physical structures and bed forms as well as biogenic structures related to bioturbation in the upper portions of such units. Deep-sea organisms that are potential producers of trace fossils include both eurybathic and stenobathic forms. Among the former are various genera of coelenterates, sipunculan, brachiopods, decapods, scaphopods and ophiuroids, which have broad depth tolerances. Among the latter are various genera of sponges, echiurans, pogonophorans, isopods, amphipods and asteroids, which have narrow depth tolerances. Unfortunately, very little information is available on which kinds of animals make which kinds of burrows in the deep sea today. Moreover, there are numerous types of ancient deep-sea trace fossils that have no recognized modern representatives. It would be inaccurate, therefore, for sedimentologists to base their paleodepth interpretations of trace fossils solely on the depth zonation of modern

The end-Permian mass extinction was associated with the onset of anoxia in widespread marine environments; however, the extent of this anoxia remains controversial. Proposed models range from near-universal “superanoxia” in the Panthalassic Basin to a more limited expansion of anoxia in the upper water column in response to enhanced primary productivity. The Peck Creek and Ursula Creek sections of northern British Columbia were deposited at ~200 m water depth in the Ishbel Trough, on the margin of cratonic North America. This trough was generally contiguous with the Slide Mountain Ocean, and thus with the broader Panthalassic Ocean, though it may have been partially separated by structural highs at various times during the Permian. Both sections include continuous Wordian to Changhsingian sedimentary successions, which span the end-Permian mass extinction boundary and continue into the earliest Triassic. The extinction is recognizable as the disappearance of biogenic silica from the environment, which defines the contact between the Fantasque Formation and overlying Grayling Formation. This surface also corresponds with the onset of anoxia, and the accumulation of redox-sensitive trace metals. The covariation trends in these metals, and in other isotopic proxies, can be used as tools to trace the degree of communication between the Ishbel Trough–Slide Mountain Ocean and the broader Panthalassic Basin. Molybdenum-uranium covariation trends indicate that the northern Slide Mountain Ocean and Ishbel Trough remained in communication with the larger global ocean throughout this interval, suggesting inversion of the Wordian structural high to form a depositional subbasin by the Changhsingian. This is in contrast to the Opal Creek section of southern Alberta, which shows evidence for some degree of restriction, suggesting that the Slide Mountain Ocean may have maintained a north–south gradient in water chemistry. Several lines of evidence suggest that this onset of anoxia was not related to expansion of an upwelling-driven oxygen minimum zone. No clear changes in primary productivity, as recorded by organic carbon or authigenic phosphorus and barium, are observed across the extinction horizon. Changhsingian nitrogen isotope values are generally in the 2 to 3‰ range, suggesting minimal denitrification at thermocline water depths, and these values decreased in the earliest Triassic, likely in response to enhanced nitrogen fixation. This suggests that anoxia was driven by shoaling of a chemocline that developed due to stratification of the Slide Mountain Ocean, rather than western-boundary upwelling effects.

ABSTRACT Fine-grained sedimentary rocks (e.g., shale, mudrock, mudstone, claystone, chert, or chalk) are the most common rocks in the stratigraphic column. They preserve the best archives of Earth’s history for interpreting paleoclimate and paleo-oceanography; influence the flow of groundwater and hydrocarbons; serve as hydrocarbon source, reservoir, and seal; and host strata-bound resources. Advancing technology has provided access to the vast energy resources contained in these rocks—indeed, the production of “shale oil” and “shale gas” in the United States changed the energy outlook almost completely over the seven-year span of 2007–2014. Sequence stratigraphy provides an organized, integrated approach to place fine-grained rocks into a firm framework alongside sandstone and carbonate. The physical, biogenic, and chemical properties of fine-grained rocks vary in systematic ways that can be deciphered and predicted within an integrated sequence-stratigraphic framework. This chapter addresses the importance of fine-grained sedimentary rocks and the challenges in their study, followed by an introduction to the key attributes of fine-grained sedimentary rocks and to their role as source, reservoir, and seal of hydrocarbon play elements. A quantitative analysis demonstrates the importance of geological factors on hydrocarbon resource-in-place and deliverability of these so-called engineering reservoir plays. The chapter then presents the rationale for applying sequence stratigraphy to fine-grained sedimentary rocks and concludes with an overview of the organization of this Memoir. The Memoir has four main sections: (1) introductory chapters that provide overviews of the significance of fine-grained rocks, their character and classification, and techniques for studying them; (2) chapters that cover the fundamentals and examples of fine-grained rocks at successively larger scales, from the lamina to sequence-set scale; (3) case studies that illustrate all these scales of stratification with examples that span the Paleozoic to the Cenozoic and deep-marine to coastal-plain and lake settings; and (4) a summary of the controls on stratal record—mechanisms and contingencies that affect sediment supply and accommodation.