Abstract The Everglades National Park is located at the southern extreme of peninsular Florida in Dade and Monroe Counties (Fig. 1). Florida 27 provides access from Homestead and Florida City to the southern part of the park and the locations discussed here.

Subsurface sandstone samples of the Upper Jurassic (Oxfordian) Norphlet Formation erg deposits and (Kimmeridgian) Haynesville Formation sabkha deposits were collected from wells in the eastern Gulf of Mexico for U-Pb detrital zircon provenance analysis. Norphlet Formation samples in southwestern Alabama are characterized by detrital zircon ages forming two dominant populations: (1) 265–480 Ma, associated with Paleozoic Taconic, Acadian, and Alleghanian orogenic events of eastern Laurentia, and (2) 950–1250 Ma, associated with the Grenville orogenies of eastern Laurentia. These detrital zircon ages indicate derivation from Laurentian and Laurentian-affinity sources, including erosion of Paleozoic strata of the remnant Alleghanian fold-and-thrust belt and Black Warrior foreland basin, as well as Laurentian cratonic rocks exposed in remnant Appalachian orogenic highlands and eastern Gulf of Mexico rift-related horst blocks. In contrast, Norphlet Formation samples from the offshore Destin Dome exhibit a major population of 540–650 Ma zircon grains, along with a small population of 1900–2200 Ma zircon grains; these ages are interpreted to indicate contribution of sediment to the Norphlet erg from peri-Gondwanan terranes sutured to eastern Laurentian, as well as from the Gondwanan Suwannee terrane, which remained attached to North America after the rifting of Pangea. Samples from south-central Alabama yield subequal proportions of four major age populations: 250–500 Ma, 520–650 Ma, 900–1400 Ma, and 1950–2250 Ma. These ages indicate sediment was sourced by both Laurentian/Laurentian-affinity and Gondwanan/Gondwanan-affinity rocks, either through a combination of these rocks in the source area, or intrabasinal mixing of Laurentian/Laurentian-affinity sediment with Gondwanan/Gondwanan-affinity sediment. Detrital zircon provenance data from the overlying Haynesville Formation clastics of the Destin Dome offshore federal lease block also show the signature of Gondwanan/Gondwanan-affinity sediment input into the eastern Gulf of Mexico, suggesting that paleotopography affecting Norphlet Formation deposition persisted throughout much of the Late Jurassic. However, samples from the Pennsylvanian Pottsville Formation synorogenic fill of the Black Warrior Basin and Middle Cretaceous Rodessa Formation marginal marine sandstone lack evidence for any significant contribution of Gondwanan or Gondwanan-affinity detritus to the basin, indicating that transport of Gondwanan/Gondwanan-affinity zircon to the eastern Gulf of Mexico was due to early Mesozoic uplift, erosion, and/or paleodrainage pattern development. These results, along with previously reported detrital zircon provenance of Triassic and Jurassic sandstone of the southern United States, suggest that early Mesozoic sediment supply in southern North America was closely associated with erosion of Gondwanan/peri-Gondwanan crust docked along the Suwannee-Wiggins suture, which likely extended westward from the Suwannee terrane to the Yucatan-Campeche terrane; much of this Gondwanan/peri-Gondwanan crust remained docked along the Suwannee-Wiggins suture after the rifting of Pangea and prior to opening of the Gulf of Mexico.

The Late Jurassic geologic record in Mongolia is poorly known, partly due to only sparsely preserved outcrops, but also because of the region's remoteness and limited body of published geological data compared to China and other parts of Eurasia. Considered in the broader context of Mesozoic sedimentary basin dynamics, the Late Jurassic record that has been studied is both informative and perplexing. Late Jurassic sedimentary basins are preserved in the subsurface throughout the country, and they are partially exposed (along with their igneous and metamorphic counterparts) where they have been inverted by Cretaceous–Cenozoic faulting. However, the speculated geodynamic settings for these basins are poorly reconciled: Various reconstructions place the basins between regions of contrasting tectonic styles in the late Mesozoic (contraction to the southwest and extension to the east/southeast). It is suggested that much of Mongolia represented a large-scale accommodation zone beginning in the early Mesozoic and continuing into at least Late Jurassic time. This scenario may have been expressed within an overall strike-slip framework that includes long-term reactivation structures, some of which are still active today. Although speculative, the hypothesis helps to explain evidence for differential rotation between Mongolia and surrounding blocks in the late Mesozoic, and it is testable pending additional field and analytical data. In particular, additional information is needed regarding the timing and modes of Mongol-Okhotsk Ocean closure and suturing. Current interpretations place final ocean closure and suturing in Mongolia anywhere from Permian to Cretaceous, with differing implications for collisional mechanisms and geologic expressions.

Abstract Cyanobacteria and/or bacteria are a major part of the biomass, although their recognition as significant constituents of the sedimentary record has largely b overlooked in rocks other than Precambrian and Paleozoic stromatolites. Their extremely small size has been one of the major obstacles in the recognition of such constituents, which can be observed properly only at high-resolution SEM imaging. Here we present evidence of accumulation of cyanobacterial “microspheroids” as predominant components of sediments of the Cenomanian–Turonian deposits in the “Sierra de Parras”, northeastern Mexico, during an interval of predominantly dysoxic to anoxic conditions. The stratigraphic section includes a sequence of limestones and marls with well-defined rhythms at the decimeter to millimeter scale. This facies shows internal structures that are arranged in nearly even-parallel “varve-like” dual laminae less than 3 mm thick. A few scattered planktonic foraminifera and radiolaria occur in the dark laminae, while the light laminae are composed almost entirely of microspheroids. Total carbonate (CaCO 3) content varies from 43.0% to 78.3%, and TOC is relatively high, between 0.3% and 3.6% (consistently higher than 1.6%), suggesting an environment favorable for preservation of organic matter. Inorganic-element concentrations (Mo, V, Cr) suggest that the sequence at Parras accumulated in a dysoxic to anoxic environment in which microbial communities were predominant, as also revealed by petrographic and SEM analyses. Microfacies reveal that compositional differences in the laminae are associated with varying abundance of cyanobacterial “microspheroids”. The distinctive laminae are the result of recurring cycles of calcareous cyanobacteria blooms, which remained dominant throughout the sedimentary sequence. Organic-carbon-rich black shales and limestones of the Parras region further document unique paleoceanographic situations during the early Late Cretaceous, when strong intermittent dysoxic or anoxic bottom conditions developed at the site of the Parras deposits and were associated with rhythmical production of cyanobacteria. Geologic Problem Solving with Microfossils: A Volume in Honor of Garry D. Jones SEPM Special Publication No. 93, Copyright © 2009 SEPM (Society for Sedimentary Geology), ISBN 978-1-56576-137-7, p. 171–186.

Abstract The Kaiparowits Basin, located mostly within Grand Staircase–Escalante National Monument, preserves an outstanding record of Late Cretaceous sedimentation in a foreland basin setting. Hosted in these rocks is one of the most continuous and complete records of this period’s ecosystems known from any one geographic area in the world. Recent work in the basin has emphasized macrovertebrate remains and documented many new sites of high scientific value. Recent stratigraphic studies have further refined our knowledge of the depositional systems and chronostratigraphic relationships. Provided is an overview of some of these recent advances, along with the necessary background to provide context .

Abstract: This study investigated the extent to which deep-dwelling, infaunal foraminifera bias modern and fossil distributions in the subtropical mangroves of the Everglades (southwest Florida), and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. Typically, these studies are based on modern analogs from the upper 1 to 2 cm of sediments, as most benthic foraminifera live in the surface 1 cm, but in tropical mangrove environments, deep-dwelling infaunal foraminifera may be more common. The vertical distributions of live assemblages in cores from a mudflat and three mangrove sites were investigated. To examine the preservation potential of dead tests, distributions of wall types and inner test linings were recorded. The living depths of benthic foraminifera showed a landward deepening from 1 to 3 cm in mudflats and low mangroves and from 7 to 10 cm in middle and high mangroves, possibly due to a landward increase in oxygenation of the subsurface sediments. Modern assemblages from the top 2 cm included species common in the deep infauna and contained, on average, 36% of the total standing crop. Additions to total assemblages at greater depths by subsurface production were negligible. Thus, the upper 2 cm of the sediment column would be sufficient as a modern analog for paleoenvironmental studies in the southwestern Everglades. Preservation of dead tests is influenced by a landward increase in the degradation of agglutinated taxa through oxidation/bacterial breakdown of organic cements. Fortuitously, calcareous taxa preserve well in the carbonate-buffered sediments of the Everglades.

Abstract The Demerara Rise is a deep-water plateau situated off the coast of South America in the equatorial Atlantic. Its geographic position makes its sedimentary record a desirable target to investigate tectonic and paleoceanographic signals in the Atlantic Ocean. Numerous mass-transport deposits (MTDs) were interpreted from seismic reflection profiles on the outer reaches of the plateau. One such MTD was drilled and sampled during Ocean Drilling Program Leg 207, Site 1261. This MTD overlies a regionally correlated middle to late Miocene unconformity that resulted from extensive erosion that caused removal of up to 220 m of sediment down to Eocene strata. Calcareous nannofossils were analyzed to determine the age of the 59-m-thick MTD lithologically described as slope conglomerate. Its age and corresponding stratigraphic sequence are used to infer possible causative factors in its emplacement. The slope conglomerate contains highly colored sandy carbonate clasts and silty-sandy turbidite rocks supported in a nannofossil-rich hemipelagic claystone matrix. The carbonate clasts are early Miocene (nannofossil Zone NN4), and the claystone matrix is late Miocene (Subzone NN11b) in age; stratigraphic relationships place the slope conglomerate sequence within nannofossil Subzone NN11b (7.2-5.5 Ma). A normal listric growth fault is located 5 km upslope of the drill site. These stratigraphic and structural relationships suggest causative mechanisms for sediment mass failure and generation of the MTDs. The age of the studied slope conglomerate provides an upper age limit (7.2 Ma) for the regional Miocene unconformity. The unconformity correlates in time with deepening of Fram Strait off Greenland, shoaling of the Isthmus of Panama, and establishment of polar glaciations. These changes resulted in intensification of bottom water currents and enhanced upwelling along continental margins throughout the Atlantic. This current intensification possibly led to increased erosion and generation of locally steep slopes along the flanks of Demerara Rise. Probable seismic activity, as indicated by the proximal shallow fault, initiated sediment mass failure and emplacement of the studied conglomerate. Similar erosion and mass-transport activity is reported throughout the Atlantic during this period of time, indicating the importance of these paleoceanographic changes to continental-margin development.