Shallow-marine, siliciclastic depositional systems are dominated by physical sedimentary processes, with penecontemporaneous cementation playing only a minor role in sediment dynamics. For this reason, microbial mats rarely form stromatolites in siliciclastic environments; instead, mats are preserved as wrinkle structures on bedding surfaces.

Microbial mat signatures should be widespread in siliciclastic rocks deposited before the Cambrian Period; however, siliciclastic shelf successions of the upper Neoproterozoic Nudaus Formation, Nama Group, Namibia, contain only sparsely distributed wrinkle structures. The facies distribution of observed structures reflects the superposition of a taphonomic window of mat preservation on the ecological window of mat development. Mat colonization is favored by clean, fine-grained, translucent quartz sands deposited at sites where hydrodynamic flow is sufficient to sweep mud from mat surfaces but insufficient to erode biostabilized laminae. During periods of reduced water agitation, microbial baffling, trapping, and binding entrain quartz grains into mat fabrics, increasing the thickness of the living mat layer. Mat preservation is facilitated by subsequent sedimentary events that bury the microbial structures without causing erosional destruction. Pressure originating from sediment loading forms molds and casts at bedding planes, inducing the formation of wrinkle structures.

In storm-influenced shelf successions of the Nudaus Formation, wrinkle structures are restricted to quartz-rich fine sandstone beds, 2–20 cm thick, that alternate with thin interlayers of sandy mud- or siltstones. Such a lithological facies developed only sporadically on the Nudaus shelf, but is common in shallow-marine siliciclastic rocks of older Neoproterozoic age exposed in the Naukluft Nappe Complex. The observed relationship between sedimentary environment and microbial mat preservation can be observed in other Proterozoic and Phanerozoic siliciclastic rocks, as well as in modern environments. This facies dependence provides a paleoenvironmental and taphonomic framework within which investigations of secular change in mat abundance must be rooted. Understanding the physical sedimentary parameters that control the formation and preservation of microbial structures in siliciclastic regimes can facilitate exploration for biological signatures in early sedimentary rocks on Earth or other planets.

The origin of meter-scale cyclicity in the type Cincinnatian Series has long been debated. Some models hypothesize that changes in water depth driven by sea-level fluctuations were responsible for producing meter-scale alternations of shale-rich and limestone-rich intervals. Other models link meter-scale cyclicity to changes in storm intensity and frequency, with no change in water depth. Previous interpretations have relied upon lithological variations, which have proven to be ambiguous with respect to meter-scale cyclicity. Here, the role of water depth in producing meter-scale lithologic patterns is assessed using gradient analysis of high-resolution fossil abundance data from the Kope and lower Fairview Formations. Studies have demonstrated that the distribution of biota in this interval is controlled by environmental variables correlated to water depth. Therefore, a direct comparison of stratigraphic variations in faunal composition to meter-scale lithologic alternations is an appropriate test of the influence of water depth on meter-scale cyclicity.

In the present analyses, ordination scores generated from faunal abundance data are grouped into bins that correspond to the upper proximal and lower distal parts of each meter-scale cycle, using three different binning protocols. For each cycle, ordination scores from the lower bin are compared to those from the upper bin; consistent differences between the two would suggest a water depth control on meter-scale biotic patterns, and, thus, cyclicity. However, results indicate no consistent correspondence of faunal patterns to meter-scale lithologic patterns, suggesting that water depth does not play a significant role in the formation of meter-scale cycles. While the different binning protocols did affect analytical outcomes in various ways, the lack of a consistent difference between upper and lower bins within each cycle was robust to all protocols. A model invoking oscillations of storm intensity and frequency appears to provide the most parsimonious explanation for the origin of Cincinnatian meter-scale cyclicity.

In this contribution theoretical morphospace techniques are demonstrated to be particularly useful in the analysis of ecomorphologic variation; that is, the detection of repetitive morphologies that consistently reoccur in similar environments. Although at least six distinct species of Archimedes occurred in the mid-Carboniferous shallow seas of North America, the distribution of a sample of 116 of their helical colony morphologies within theoretical morphospace forms two clouds of points that correspond to two paleoenvironmental settings: basinal versus back-shoal. It is argued that the distribution of the two Archimedes ecomorphologic colony types in morphospace is a function of the vertical extent of the quiet-water zone above the sea floor in back-shoal versus basinal environments, and not of differences in colony-type feeding efficiencies. It also is argued that the observed tendency of back-shoal colonies to form geographically distinct morphologic populations in morphospace is a function of their clonal mode of reproduction, in contrast to the more commonly sexually-reproducing basinal colonies.

Theoretical morphospace analyses also can reveal species that do not show ecomorphologic variation in colony form. The unusual species Archimedes laxus, which occurs in both basinal and back-shoal environments, occupies its own unique position within the theoretical morphospace, a position that is displaced from and does not overlap the regions of morphospace occupied by other colonies, either basinal or back-shoal. Consideration of the unique aspects of this species' morphology leads to the suggestion that A. laxus may have had a rapid growth, weed-like mode of life that was quite different from typical Archimedes colonies.

Unusual fossil macrofloras from South America (Peru, Bolivia, Brazil), Africa (Niger), India, and Australia are distinctly different from both the Early and Late Carboniferous floras of Gondwana. These floras can be correlated with each other based on macrofloral and palynologic composition, and dated as Late Visean to earliest Serpukhovian through palynologic data from several floras and isotopic data from Australia. The floras are dominated by pteridosperm foliage and characterized by the occurrence of tree-lycopsids, and represent a warm-temperate, frost-free floral belt in Gondwana that reached from 30° to as far as 60° South that existed directly before the onset of the major episode of the Carboniferous glaciation. The plants lived during an interval of very warm climate as indicated by the width and extent of the floral belt, conditions that facilitated the migration of plants into this area from other parts of the globe. The term Paraca floral realm is redefined and extended to include all of these Late Visean-earliest Serpukhovian floras throughout Gondwana.

Sedimentary models that apply to the Middle Miocene succession in Amazonia are controversial. Although tidally-influenced sedimentary deposits have been described from several locations, the identification of brackish-water or marine facies has been hampered by limited outcrop exposure. Also, ichnological data largely have been ignored.

This study focuses on ichnological and sedimentological relationships observed in outcropping strata of the Solimoes Formation (Middle Miocene) along the Acre River in western Brazil and northern Bolivia. The studied strata comprise a fine-grained lower unit that is sharply overlain by dipping, interbedded sands and muds, known as inclined heterolithic stratification (IHS). The IHS is present throughout the length of the outcrop, about 80m. The outcropping strata are interpreted to represent two depositional subenvironments: (1) A lower unit that resulted from sediment accumulation in a shallow, restricted, subaqueous depositional environment. The deposit ultimately became emergent with subsequent paleosol development. (2) An upper unit dominated by marginal marine point-bar deposits that developed in a channel. Trace fossils observed in the upper unit provide evidence that mesohaline waters occupied the channel at the time of sediment accumulation. This is supported most strongly by the presence of Scolicia, a common marine trace fossil, and reburrowed (composite) Ophiomorpha. The resultant ichnofabric represents a response to sedimentary events that demonstrates the IHS beds reflect seasonal or annual cyclicity.

The analysis of the river-exposed outcrop at Boca de Santa Pedro, Brazil, leads to four conclusions: (1) the IHS exposed in the upper portion of this deposit are possibly tidally influenced and almost certainly accumulated in a brackish-water channel; (2) if IHS are bioturbated, their temporal significance can be assessed; (3) seasonal fluctuations in discharge were significant enough to alter depositional and biological processes in this paleochannel, and; (4) brackish-water incursion into Amazonia during the Middle Miocene can be traced as far south as northern Bolivia.

The Main Glauconite Bed (MGB), near the top of the Eocene Stone City Member (Crocket Formation), Texas, has been considered to contain a typical local paleocommunity (parautochthonous assemblage formed within a stable habitat). Microstratigraphic analysis, however, reveals a complex sedimentologic and taphonomic history for the MGB, a unit that is 1.7–1.9 m thick and consists of three intercalated small-scale facies interpreted to represent differing modes of deposition. The primary autochthonous inner-shelf sediments are dark glauconitic clay-silts with a matrix-supported polytaxic fossil assemblage. Recurrent storms produced thin (few mm to cm) layers of mostly simple, bioclast-supported, polytaxic shell concentrations. These distal tempestites occur mainly as small-scale lenses and as a few beds and pods, associated with glauconite-pellets, terrigenous sands, and scarce sedimentary structures. Subsequent burrowing destroyed most skeletal concentrations and formed patches of fossils, glauconite-pellet sand, and terrigenous, very fine sand. The assemblages in the three facies are dominated by corbulids, naticids, turrids, noetiids, and the solitary coral Turbinolia sp., and are indistinguishable based on their taxonomic composition and most of the taphonomic features (disarticulation, fragmentation, incrustation, corrasion, shell repair, and predatory drill holes). Only drilled shells are significantly more abundant in the bioturbated patches than in the two other facies. The only strong evidence for the presence of allochthonous faunal elements is the lack of right valves of anomiid bivalves. The scarcity of significant differences between facies indicates the presence of one basic paleocommunity that was modified by small-scale and short-term depositional events and bioturbation, but which can still be recognized in spite of having been preserved by three different suites of depositional processes. Microstratigraphic analysis of bioclastic deposits can recognize small-scale sedimentologic and biostratinomic processes that otherwise frequently are overlooked in paleoecological studies. Such processes have only minor influence on taxonomic composition and taphonomic features, which are therefore robust characteristics of a fossil assemblage.

Although reefs often are expressed as single structures in the geological record, they are in fact composites of many superimposed communities. Therefore, an understanding of the processes of reef formation is largely dependent upon description of the life cycle of the dominant reef-building organisms. Modern reef corals commonly show synchronous gamete release (mass spawning) but, to date, such a phenomenon has not been reported from the fossil record. The first example of where the life cycle and reproductive ecology of an ancient reef-builder can be tentatively reconstructed is presented herein. Exceptionally preserved specimens of the widespread Late Paleozoic phylloid alga Eugonophyllum (Family Halimedaceae, Order Bryopsidales, Division Chlorophyta) allow the recognition of simultaneously ruptured reproductive structures. This may offer evidence for the synchronous release of gametes. In some modern bryopsidaleans, such as Halimeda and Udotea, synchronous reproduction is followed frequently by mass mortality of the community. It is speculated that phylloid algal reefs may be understood as having formed by the density-dependent recruitment of many self-seeded generations, which produced short-lived populations that reached reproductive maturity after six months to two years, but then suffered mass mortality on spawning the next generation. Those algae that formed a reef framework, as opposed to a bioclastic bed, were associated with an encrusting medium, most commonly microbialite. Recognition of such a life cycle may offer important insights into the expression of such reefs in the geological record that often are dominated by sheets of densely-packed, fragmentary material.

A deep-tier, bow-form burrow with a long apertural neck, and several different types of infill is described from Upper Jurassic shelfal carbonates of Saudi Arabia, Miocene pelagic packstones and wackestones of Malta, and Lower Cretaceous shoreface sands and mudrocks of southern England. The two most commonly observed types of infill are a coarse-grained infill, referred to as Glyphichnus-mode (formed by sediment entering the burrow following breakage of the apertural neck), and a laminated, muddy infill, referred to as Cylindrichnus-mode, which is considered to represent passive, draught filling through a complete burrow. The type of infill and aspects of preservation show that these burrows can be used to assess the style of sedimentation, particularly steady aggradation versus periodic erosion. At present the bow-form burrow is not assigned to a specific ichnotaxon.