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Early study of what is now called the Opohonga Limestone in west-central Utah indicated that it was part of a massive formation of Carboniferous age. Later studies identified fossils from the formation's older carbonates that were known to be Early Ordovician. A significant conodont fauna from a section on Gardison Ridge permits an even more precise definition of the formation which includes correlation with the classic North American Ibexian sequence of western Utah. While an important part of the earliest Ibexian sequence is missing on Gardison Ridge, the Opohonga Limestone there contains conodont elements representing seven zones and subzones of the type Ibexian and can be firmly correlated with conodont zones of the upper House and most of the Fillmore Formations of the Pogonip Group in the Ibex area. This correlation also confirms that the Sauk III–IV sequence boundary occurs in the lower part of the formation. The oldest conodont faunas of the Ibexian Series were not recovered from the lowe...

In central Utah, the major pre-Mississippian unconformity is fairly well understood at most of the localities where it is recognized. However, the unconformity is more enigmatic in Rock Canyon of the central Wasatch Range. At this locality, dolomitization of most pre-Mississippian rocks obscures stratigraphic identification of Devonian and older units. The absence of any identifiable angular relationship further complicates resolution. Because of this, both identification of the stratigraphic level of the unconformity and, consequently, its magnitude remain controversial. Large-size dolomite samples taken in Rock Canyon at closely spaced intervals for the 3.6-m directly below definite Upper Devonian rocks yield microfossils, including conodonts, in the uppermost 1.6-m of that interval that indicate no unconformity exists between the Cambrian Maxfield Limestone and the Upper Devonian-Lower Mississippian Fitchville Dolomite at the horizon previously identified as unconformable. Rather, an unknown thickness of dolomitized Upper Devonian Pinyon Peak Formation and probable older rock (possibly Bluebell Dolomite and Victoria Formation) occurs between the top of definite Maxfield and base of the Fitchville. The identification of the unconformity horizon remains unknown. Our preliminary work outlines a promising procedure for future understanding of the magnitude and stratigraphic level of the unconformity.

Two piston cores from the Eurasian flank of Lomonosov Ridge near lat 88.9°N, long 140°E provide the first samples of bedrock from this high-standing trans-Arctic ridge. Core 94-PC27 sampled nonmarine siltstone similar in facies and age to uppermost Triassic to lower Lower Jurassic and mid– Lower Cretaceous beds in the 4 to > 5 km Mesozoic section on Franz Josef Land, on the outer Barents shelf. A ca. 250 Ma peak in the cumulative frequency curve of detrital zircons from the siltstone, dated by U- Th-Pb analysis, suggests a source in the post-tectonic syenites of northern Taymyr and nearby islands in the Kara Sea. Textural trends reported in the literature indicate that the Lower Jurassic nonmarine strata of Franz Josef Land coarsen to the southeast; this suggests the existence of a sedimentary system in which detrital zircons could be transported from the northern Taymyr Peninsula to the outer Barents shelf near the position of core 94-PC27 prior to opening of the Eurasia Basin. Correlation of the coaly siltstone in core 94-PC27 with part of the Mesozoic section on Franz Josef Land is compatible with the strong evidence from seafloor magnetic anomalies and bathymetry that Lomonosov Ridge is a continental fragment rifted from the Barents shelf during the Cenozoic. It also suggests that Lomonosov Ridge near the North Pole is underlain by a substantial section of unmetamorphosed Mesozoic marine and nonmarine sedimentary strata. Core 94-PC29 sampled cyclical deposits containing ice-rafted debris (IRD) overlying weakly consolidated laminated olive-black anoxic Neogene siltstone and mudstone with an average total organic carbon (TOC) of 4.1 wt%. The high TOC content of the mudstone indicates that during the Neogene, prior to the introduction of IRD into the Arctic seas about 3.3 Ma (early late Pliocene), the shallow waters of the central Arctic Ocean supported significant primary photosynthetic organic production near the North Pole. These deposits also contain fine grains of siltstone that resemble the breccia-clast siltstone of core 94-PC27 and reworked Carboniferous, Cretaceous, and Tertiary palynomorphs that may have also originated in the bedrock of Lomonosov Ridge.

Phosphatic microfossils including probable microvertebrates occur in the Early and Middle Ordovician rocks of Wisconsin. The eight types described here include the probable ostracoderm Anatolepis, and six unidentified but possible vertebrate fragments as well as the palaeoscolecid worm Milaculum. These fossils are rare, but at two localities several specimens per kg were recovered over significant stratigraphic intervals. The high concentration of certain fossils in the lower part of the Galena Group suggests that there is stratigraphic value in their description. Identification of similar material or of articulated assemblages of these fossils may eventually lead to identification of biologic affinities.

Phosphatic microfossils including copious microvertebrates and conodont elements indicative of the upperIcriodella discreta–Icriodella deflectaZone (Aeronian) are found in a single bed of the Hendricks Formation, Burnt Bluff Group, Sturgeon Bay, Wisconsin. Scales of thelodonts, includingLoganelliasp. cf.Loganellia sibericaKarajute-Talimaa, 1978, and rareValyalepis cristaTurner (inTurner and Nowlan, 1995) predominate among the microvertebrate remains. Most scales are referred toZuegelepis potanusTurner new genus and species. Associated with the thelodont scales are rare phosphatic fragments of questionable dermal “bone” and scales, possibly of heterostracan origin. Thelodont scales are also found in the Hendricks Formation at Fayette State Park, Michigan and in the subsurface Byron Formation (Burnt Bluff Group) in Schoolcraft County, Michigan.

Cores from Northwind Ridge, a high-standing continental fragment in the Chukchi borderland of the oceanic Amerasia basin, Arctic Ocean, contain representatives of every Phanerozoic system except the Silurian and Devonian systems. Cambrian and Ordovician shallow-water marine carbonates in Northwind Ridge are similar to basement rocks beneath the Sverdrup basin of the Canadian Arctic Archipelago. Upper Mississippian(?) to Permian shelf carbonate and spicularite and Triassic turbidite and shelf lutite resemble coeval strata in the Sverdrup basin and the western Arctic Alaska basin (Hanna trough). These resemblances indicate that Triassic and older strata in southern Northwind Ridge were attached to both Arctic Canada and Arctic Alaska prior to the rifting that created the Amerasia basin. Late Jurassic marine lutite in Northwind Ridge was structurally isolated from coeval strata in the Sverdrup and Arctic Alaska basins by rift shoulders and grabens, and is interpreted to be a riftogenic deposit. This lutite may be the oldest deposit in the Canada basin. A cap of late Cenomanian or Turonian rhyodacite air-fall ash that lacks terrigenous material shows that Northwind Ridge was structurally isolated from the adjacent continental margins by earliest Late Cretaceous time. Closing Amerasia basin by conjoining sea-floor magnetic anomalies beneath the Canada basin or by uniting the pre-Jurassic strata of Northwind Ridge with kindred sections in the Sverdrup basin and Hanna trough yield similar tectonic reconstructions. Together with the orientation and age of rift-margin structures, these data suggest that (1) prior to opening of the Amerasia basin, both northern Alaska and the continental ridges of the Chukchi borderland were part of North America, (2) the extension that created the Amerasia basin formed rift-margin grabens beginning in Early Jurassic time and new oceanic crust probably beginning in Late Jurassic or early Neocomian time. Reconstruction of the Amerasia basin on the basis of the stratigraphy of Northwind Ridge and sea-floor magnetic anomalies in the Canada basin accounts in a general way for the major crustal elements of the Amerasia basin, including the highstanding ridges of the Chukchi borderland, and supports S. W. Carey9s hypothesis that the Amerasia basin is the product of anticlockwise rotational rifting of Arctic Alaska from North America.

A diverse assemblage of acritarchs, prasinophytes and dinoflagellate cysts occurs in an organic rich black mud in Core Fl-533, taken from the Alpha Ridge, Arctic Ocean. Similarities between this assemblage and others described from the Canadian Arctic allow this black mud to be dated as early Maastrichtian, based primarily on the presence of Cerodinium leptodermum, and the absence of exclusively Campanian and upper Maastrichtian taxa. The high abundance of Comasphaeridium and marine derived amorphous organic matter may indicate a shelf to upper slope environment, possibly deposited during a marine transgression. An abundance of prasinophyte algal cysts, a moderately high peridinioid/gonyaulacoid dinoflagellate cyst ratio, and high species diversity indicate high paleoproductivity, most likely associated with upwelling conditions. When interpreted within the context of two nearby biosiliceous-rich Maastrichtian cores also taken from Alpha Ridge, and from paleogeographic reconstructions, these results indicate that an upwelling region probably existed along the eastern Arctic Ocean during at least part of the Maastrichtian, and formed different sedimentary facies in shelf to slope environments, similar to facies patterns recognized in lower latitude paleo-upwelling regions.

Conodonts are present in the basal part of six Arctic Ocean sediment cores recovered from the Northwind Ridge in the Chukchi Borderland area of the western Arctic Ocean. The conodonts include species typical of the Upper Cambrian, Lower and Middle Ordovician, Middle to Upper Pennsylvanian, probable Lower, middle and Upper Permian, and Lower Triassic. Most of the conodont elements, including a few of the Cambro-Ordovician and all of the Upper Permian species, were recovered from the sand fraction of the Northwind Breccia in the basal 1.5 m of core 92-P34. Other Ordovician and younger Paleozoic conodont specimens occur in carbonate clasts incorporated in the Northwind Breccia. The talus breccia occurs in the lower part of the Early Pliocene/Miocene unit A (undifferentiated) and is overlain unconformably by Pleistocene age sediment. A few Paleozoic and Triassic conodonts also occur in clasts recovered from the basal parts of five other Northwind Ridge cores. Upper Permian specimens are the most numerous of the conodont elements and occur together with an abundant ichthyolith assemblage. In addition, the sand fraction of the Northwind Breccia contains poorly preserved foraminifera, holothurians, and sponges spicules that are common in all Arctic Ocean Plio-Pleistocene sediment. Occurrence of conodonts in what is interpreted to be talus derived from bedrock indicates that the enigmatic Northwind Ridge is a true continental fragment that includes marine strata of at least Paleozoic and Triassic age. The nature of the conodonts and other fossils recovered from the breccia suggests that the Northwind Ridge originated as part of the Canadian Arctic Islands.

The composition of Pleistocene ice-rafted debris (IRD) >250 gm was analyzed quantitatively by grain counting in five sediment cores t¾om the western central Arctic Ocean and compared with the composition of till clasts from NW Canada in order to determine the dropstone origin and to reconstruct the Pleistocene ice drillways and surface currents. The IRD composition alternates repeatedly between carbonate- and quartz-dominated assemblages, along with metamorphic and igneous rocks, clastic rocks, and some chert. The highest quartz content is found on the Alpha Ridge, while carbonate percentages are highest on the Northwind Ridge (NWR) and the Chukchi Cap. The source for the carbonates is the area around Banks and Victoria Islands and parts of northern Canada. Quartz most likely originated from the central Queen Elizabeth Islands. IRD on the southeastern Alpha Ridge is dominated by mafic crystalline rocks from northern Ellesmere Island and northern Greenland. At least six major glacial intervals are identified within the last 1 million years, during which icebergs drifted toward the west in the Beaufort Sea, straight northward in the central Arctic Ocean, and northeastward on the SE Alpha Ridge.

The Arctic Ocean's link to the lower latitude World Ocean during the Late Cretaceous and early Cenozoic is puzzling. The tectonic development of the Arctic Ocean evidently included termination of the Pacific-Arctic connection late in the Cretaceous, and the Atlantic link was not significant until at least the Eocene. Yet, during the Late Cretaceous Arctic Ocean mollusks indicate that there was no more than partial restriction, and Late Cretaceous and middle Eocene phytoplankton species are the same in both the Arctic and World Ocean. Sr isotope ratios of fish associated with the phytoplankton are higher than that accepted as the World Ocean's ratios for any time during this interval, yet these high ratios do not indicate an isolated Arctic Basin. The Arctic was linked with the World Ocean and the best evidence for this is the phytoplankton similarity, but the location of the marine connection remains enigmatic.

Pliocene sediment from the central Arctic Ocean was reported first some 25 years ago. Although the basis of the Pliocene age was tenuous, none of the data subsequently presented have invalidated the original Pliocene age report. New data confirm the earliest report as well as establish the presence of older Miocene sediment. The Pliocene sediment recovered from the central Arctic Ocean to-date includes only 2–3 m of silty lutite consisting largely of illite, kaolinite, and chlorite, with lesser amounts of expandable clays, abundant Fe-Mn micronodules, but few fossils. The Pliocene age is based on extrapolation of sedimentation rates from paleomagnetic boundaries, arenaceous foraminifera, and 87 Sr/ 86 Sr isotope ratios obtained from Fe-Mn micronodules and compared to established seawater 87 Sr/ 86 Sr isotope ratios for this time. Notably absent in all except the upper part of the central Arctic Ocean Pliocene sediment is coarser-grained glacially ice-rafted debris (IRD) or any indication of measurable surface water productivity. Early interpretations of the Arctic Ocean record included the concept that sea ice was present during the Pliocene, and that the ice-cover existed more or less continually to the present. Late Cenozoic warming events that may have temporarily removed all or part of the Arctic Ocean's ice were thought to be restricted to the Pleistocene. More recently, published data suggest that the Pliocene Arctic Ocean was a warmer, perhaps ice-free ocean. General Circulation Modeling experiments with all or parts of the Arctic ice-cover removed are cited in support of Pliocene data generated primarily from the Arctic Ocean's margins that have suggested a warmer ocean. While there is important evidence for a warmer Pliocene Earth, the data to support significant warming in the central Arctic Ocean remains ambiguous. Reevaluation of part of the data used to support supposed Pliocene warming intervals on the Arctic Ocean's margins suggests that at least some of the implied Pliocene warming events may have actually occurred during the Pleistocene. The central Arctic Ocean's Pliocene record studied to date indicates only that the ocean had very low surface water productivity and extremely low sedimentation rates, both consistent with the presence of an ice-cover. There is little evidence of organic activity of any kind. However, the sum of the data obtained is equivocal concerning the affect of a warmer Earth on the central Arctic Ocean and the presence or absence of sea ice.

More than 40 species of siliceous microfossils are present in both T-3 core Fl-437 (Cretaceous) and in core Fl-422 (Eocene) from the central Arctic Ocean. Previous identifications of the silicoflagellates were the basis of the ages for these cores, but diatoms of the two cores, previously unidentified, suggest that Fl-437 could be as old as Campanian rather than middle to late Maastrichtian and that Fl-422 may be early to middle Eocene rather than middle to late Eocene. Identification of archaeomonads and ebridians completes the cataloging of the known biosiliceous assemblages of the older Arctic Ocean.Strong seasonality for the Late Cretaceous and early Cenozoic Arctic Ocean is suggested from alternating layers of vegetative cells and resting spores in both cores. The abundance of fossils is interpreted as evidence for seasonal upwelling in a nutrient-rich and much warmer Arctic Ocean. No evidence of seasonal ice or of ice-rafting is present. The profound climate change from the warmer older Arctic Ocean to the ice-covered condition of the present occurred after deposition of the sediment of Fl-422.

During the 1979 Lomonosov Ridge Experiment (lorex), 12 short gravity cores were collected from the Fram Basin part of the Eurasian Basin on the eastern flank of the Lomonosov Ridge. Sediments of these cores are organized into 11 lithologic units that constitute the first stratigraphy for any part of the deeper Eurasian Basin. Foraminifera are the same species that have been described elsewhere in the central Arctic Ocean, but are abundant only in the uppermost part of the cores.Neogloboquadrina pachyderma is the most abundant species, but the presence ofEponides tumidulus horvathi andStetsonia arctica in core SSK-2 provide a general chronologic framework for interpreting the Fram Basin sediment. The stratigraphy (a-k) is unique and is only partially correlated with other sediments of the North Polar region including that of the adjacent Lomonosov Ridge and Makarov Basin (=Amerasian Basin). Differences in stratigraphies of the Lomonosov area are interpreted to be at least in part the result of winnowing by turbidity currents and by currents crossing the Ridge from the Fram Basin toward the Makarov Basin. The sediment consists of silty lutites and sandy lutites, as well as laminated lutites interpreted to have been deposited as a result of glacial-marine and turbidite sedimentation. These short cores document the same sedimentary processes in part of the Arctic Ocean east of the Lomonosov Ridge as have been previously reported for the western Amerasian Basin.

Because no sediment of post-Eocene to Late Miocene or Pliocene age has been recovered from the central Arctic Ocean, oceanographic conditions during the middle Cenozoic are unknown. The oldest late Cenozoic sediment is glacial-marine and contains agglutinated foraminifera. A few calcareous organisms are present in the oldest late Cenozoic sediment (with an age of 2–4 Ma) but at approximately the time as deposition of lithostratigraphic unit F, sometime between 2.0 and 1.5 Ma, there was an abrupt and dramatic increase in calcareous species diversity and abundance in the central Arctic Ocean. Many of the newly introduced species are Atlantic in origin. Preliminary evidence suggests that the introduction of a moderately large and diverse calcareous fauna at this time corresponds to the lowering of the Arctic Ocean CCD level and this may be explained by increased circulation with the Northern Greenland Sea. Details of the change in threshold values in the Fram Strait required for the introduction of relatively warmer and carbonate-rich water into the central Arctic Ocean are unknown. There is evidence that spreading rates along the North Atlantic-Nansen Ridge System increased during the Pleistocene and this may have permitted increased circulation between the North Atlantic and the central Arctic Ocean. This important change in Arctic Ocean circulation corresponds to increased Pleistocene seasonality in the Northern Hemisphere.

Serious study of Carboniferous conodonts in China has been in progress only during the last ten years and encouraging achievements, especially in conodont biostratigraphy, have been made. A complete Carboniferous conodont sequence has been recognized and a preliminary biofacies framework has been established. It is now possible to recognize at least three broadly defined conodont biofacies at positions along an environmental gradient that includes basinal, outer shelf and inner shelf facies. Basinal facies are limited in distribution to South China. Outer shelf facies occur over most of the area of the platform of South China and inner shelf facies are distributed over a limited area of South China as well as the vast area of the platform of North China.

Recent proposals for deep Arctic Ocean drilling [COMPLEX, 2000; JOIDES, 2001] are significant steps toward an eventual understanding of the geologic framework, plate kinematics, and Cretaceous and Cenozoic environmental history of the north polar ocean. Because the proposals are subject to a variety of fiscal uncertainties, however, deep drilling in the ice-covered ocean could be years away from initiation. However, even in the absence of drilling, significant data concerning the geologic framework and Cretaceous-to-Eocene and late Cenozoic paleoenvironment of the Arctic Ocean basin have developed from piston cores collected from crests and flanks of Arctic Ocean ridges. While deep drilling is needed to test and amplify the commonly incomplete piston core record, some piston cores already have acquired firm data on lithology age, and paleoenvironment of Cambrian-to-Tertiary bedrock in parts of the Alpha, North wind, and Lomonosov Ridges (Figure l), and additional piston coring may be the best choice for immediate additional Arctic Ocean research.

The Oneota and Shakopee Formations of the Lower Ordovician Prairie du Chien Group of Wisconsin and Minnesota are readily differentiated on the basis of their distinctive conodont faunas. These faunas are part of the North American Midcontinent Province fauna (NAMP). The Oneota Formation contains elements of Ibexian fauna C, and represents the upper Skullrockian Stage of the Ibexian Series. The Shakopee Formation contains elements of Ibexian fauna D (NAMP), and represents at least part of the lower Stairsian Stage. The Skullrockian-Stairsian boundary and Ibexian C-D faunal boundary correspond to the Oneota-Shakopee disconformity. The Skullrockian and Stairsian Stages are the only stages of the Ibexian Series represented in the Prairie du Chien outcrop area studied for this report. Strata of the Shakopee in its type area at Shakopee, Minnesota, contain conodont elements of Ibexian fauna C. We interpret these strata to represent older strata of the Oneota Formation instead of younger, Stairsian-age strata of the Shakopee Formation, and accordingly, we reassign these strata to the Oneota.

Most previous references to the depth of the Arctic Ocean calcite lysocline have been based on comparison with the known North Atlantic carbonate compensation depth. Foraminifera from cores taken at depths ranging from 2316 to 3956 m provide the first firm calcite lysocline constraints for the central Arctic Ocean. These data suggest progressive lowering of the calcite lysocline to at least 3956 m during the past ˜1.5 m.y., interrupted by 300-m rises of the lysocline level that apparently correspond with interglacial and early glacial climate conditions. Most cores from less than 2450 m indicate variable foraminifera abundance but continual presence of foraminifera for the past ˜1.5 m.y. Low abundances commonly occur in coarse-textured sediment and are interpreted to represent low productivity during major deglaciations. Within certain equivalent lithostratigraphic units representing the past ˜1.5 m.y. there is an absence of foraminifera in cores from depths greater than 2450 m. This absence of foraminifera is interpreted to be due to dissolution. Dissolution intervals are associated with fine-grain sediments interpreted to represent interglacial and early glacial climate conditions. The interpretation of a rise in the lysocline level during interglacials is in apparent disagreement with studies reported from lower latitudes in the Atlantic Ocean but is complementary with the hypothesis that formation of Norwegian-Greenland Sea Deep Water (NGDW) and cold Canada Basin Deep Water occurs during interglacials. Paleocurrent data from the Lomonosov Ridge and the adjacent Makarov Basin are interpreted to indicate that during periods of increased glacial ice influx into the Arctic Ocean system there was reduced current activity in the bottom and intermediate water masses relative to periods when little glacial ice was present. This is in accord with the idea that NGDW affects intermediate and deep water circulation in the central Arctic Ocean and hence the calcite lysocline level.

The Lomonosov Ridge divides the Arctic Ocean into two basins with different histories. The older Amerasian Basin consists of a ridge-basin complex reflecting multiple tectonic cycles that are poorly understood. The younger Eurasian Basin includes the present Arctic Mid-Ocean Ridge. Its origin is linked to Cenozoic spreading. The entire older sediment record of the Arctic Ocean is known from only four short piston cores, all recovered from the Alpha Ridge of the Amerasian Basin. The oldest sediment recovered is a single core of black mud consisting of abundant terrestrial plant material deposited in a marine environment. Dinoflagellates are late Campanian. The black mud resulted from rapid accumulation of organic matter rather than from any of the well-known Cretaceous anoxic events. Two cores taken 100 to 200 km from the black mud consist of late Maastrichtian siliceous ooze of diatoms and silicoflagellates. This sediment has been interpreted to represent oceanic upwelling and high productivity in the Late Cretaceous Arctic Ocean. A Paleogene core consisting of similar biogenic silica has been recovered approximately 100 km from the Cretaceous cores. Silicoflagellates of this core are either Paleocene or middle to late Eocene. The sediment, like that of the Maastrichtian cores, has been interpreted to represent oceanic upwelling and high productivity. The older Arctic cores were recovered as a result of fortuitous sampling in areas of thin late Cenozoic sediment. All other Arctic cores consist of late Cenozoic sediment. The older sediment record is strong evidence of a Late Cretaceous to early Paleogene Arctic Ocean with no perennial ice and with high productivity of dinoflagellates or siliceous organisms in water that circulated with lower-latitude oceans. Recent modeling predicts some of the same climatic and oceanographic events recognized in the oldest sediment of the Arctic Ocean. The sequence of events from a warm Arctic Ocean to an ice-covered condition involved circulation changes, seasonality, and uneven spreading rates that increased North Atlantic-Arctic ventilation.

The well-exposed and fossiliferous Permian carbonates in China have yielded Early and Late Permian species of the Sweetognathus complex that permit worldwide stratigraphic evaluation of members of the group. The sporadic appearance of species of Sweetognathus and related genera throughout the Permian in western North America and Iran, in particular, may represent iterative evolution and homeomorphy. The pectiniform element morphologies of the several species are interpreted as most important for evolutionary studies and document a partial Permian biostratigraphy in China that aids in the interpretation of less complete sequences elsewhere. A new genus, Pseudosweetognathus, and four new species, Pseudosweetognathus costatus, Sweetognathus subsymmetricus, S. paraguizhouensis, and Iranognathus nudus, are described.

Correlation of Pleistocene paleoceanographic events across parts of the polar seas is accomplished with core MG-123, from the Swedish YMER-80 cruise. The 8.72 m sediment core, one of the longest recovered from any part of the Arctic Ocean, contains abundant microfossils and coarser grain sediment that are useful in interpretation and correlation of Pleistocene events with shorter sediment cores in the central Arctic Ocean. Faunal and sediment correlations are constrained by δ 18 O correlations and a time series analysis that matches several possible sedimentation rates for MG-123 with central Arctic Ocean sedimentation rates and provides a best fit correlation of the cores. The results of this study provide the first correlation of northern Greenland Sea (=southern Arctic Ocean) sediment with that of the central Arctic Ocean, more than 1000 km distant. Oceanic circulation patterns between the areas during the Pleistocene involved increased circulation during interglacials with reduced circulation during glacials. Subpolar water was not present in the northern Greenland Sea during the past 600,000 years. During this time, alternating phases of the climate cycle show a strong relationship to the 100,000 year Milankovitch cycle.

Perhaps the oldest sediment yet recovered from the central Arctic Ocean is a black, organic carbon-rich mud of late Campanian or Maastrichtian age. The sediment is known in a single piston core, F1-533, taken from the eastern Alpha Ridge. The black mud has an average organic carbon content of 14 wt % and contains abundant woody plant fragments and pollen in addition to amorphous organic matter in a marine dinoflagellate-rich matrix. Moderate hydrogen and high oxygen indices determined by Rock-Eval pyrolysis suggest a substantial contribution of terrestrial plant debris to the marine sediment. The black mud is younger than organic-rich strata deposited during the Oceanic Anoxic Events proposed for Aptian-Albian and late Cenomanian to early Turonian times in the Atlantic and Pacific oceans. The high content of organic carbon and the abundance of terrestrial organic matter in the Arctic black mud suggest a marine setting influenced by an abundant supply of organic detritus rather than by a low level of oxygenation in the water column. Sediment in this core demonstrates that the central Arctic Ocean may have been in existence by the late Campanian to Maastrichtian and that the area of core F1-533 probably was adjacent to an eroding vegetated land mass.

TheNeogondolella serrata(Clark and Ethington) group was originally reported as a North American provincial conodont lineage. More or less complete Permian sequences now recognized in China include species originally thought to be part of the North American provincial fauna as well as species reported previously from other parts of the world. Comparison of Chinese and North American species may be useful in correlation of series and stage boundaries between the two areas. The Chinese conodont succession demonstrates that most Permian neogondolellids were not provincial but attained worldwide distribution. Late Permian ancestors of Early TriassicNeogondolellaspecies were apparently widespread in the Tethyan Sea and the sudden appearance of TriassicNeogondolellaspecies in North America without Permian ancestors is only the consequence of the absence of the latest Permian marine rocks in North America.Of particular regional stratigraphic interest is the occurrence of the North American speciesN. wilcoxiClark and Behnken in the Chinese late Guadalupian-Dzhulfian. This occurrence supports a late Guadalupian (post-Lamar) age for the uppermost Gerster Formation in Utah.

Quantitative determination of biogenic silica in Late Cretaceous and Paleogene deep-sea sediment cores from the central Arctic Ocean provides evidence of open-ocean polar upwelling. The timing of polar upwelling coincides with periods of a weakened meridional thermal gradient, suggesting that heat transport to the poles by oceanic circulation may have been important. The timing of biogenic silica deposition in the Arctic precedes its deposition in both the Norwegian—Greenland Sea of the North Atlantic and he Bering Sea of the North Pacific. Tectonic events may be resposnible for the timingg and sitting of sites of deposition of biogenic silica in high northern latitudes, particularly the tectonic evolution of sites of deep-water exchange between the Arctic and the world ocean. We outline three phases in the post-mid-Cretaceous history of silica deposition in high northern latitudes. During Phase I, the Arctic is a silica sink, with deep-water formation but with no deep-water outflow. The transition to Phase II is brought about by opening of the Svalabard—Greenland Strait to deep-water outflow from the Arctic to the Norwegian—Greenland Sea. The transition to Phase III is initiated by submergence of the Faroe—Iceland Ridge and deep-water outflow from the Arctic to the North Atlantic. Climatic conditions in the Arctic during Late Cretaceous and Paleogene time are predicted to have favored open-ocean upwelling due to a circulation pattern dominated by cyclonic conditions, resulting from the establisment of a semi-permanent atmospheric low over the Alpha Ridge. Bathymetry of the Alpha Ridge may have intensified paleo-upwelling.

Many of the interesting relationships between embryologic growth and evolutionary development have been summarized by de Beer (1958). De Beer ably illustrates how the synthesis of embryology and evolution has produced plausible explanations for many biological and paleo-biological phenomena which formerly were thought to be explained best by the "recapitulation theory" of Haeckel. In many cases, these phenomena illustrate that the opposite of recapitulation occurs, and it appears valid now to accept heterochrony and its various effects as an explanation of many aspects of evolution. Little has been published on the embryologic effects in paleontology. De Beer and Swinton (1958) have cited the work on trilobites by Stubblefield (1936), graptolites by Elles (1923), and the discussion on corals by Cloud (1948) as a few works of special importance, and have concluded that similar illustrations of embryology and evolution are probably "found in the evolutionary history of most large and successful groups" (p. 2). In support of this statement can be added a few details concerning the abnormally coiled ammonoid cephalopods of the Texas Cretaceous.

Magnetic reversal data from T-3 cores indicate a sedimentation rate of 1.0 to 2.6 mm per 1000 years for the last 4 million years. Foraminifera and associated detritus suggest that the Arctic has not been warmer than at present for at least 1½ million years. There is some correlation between Foraminifera distribution and magnetic reversal boundaries but the meaning of this is not understood.

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion + or - 20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.

The deeper Arctic Ocean is conveniently divided into two unequal portions. The Amerasian Basin is the larger. It is separated from the smaller Eurasian Basin by the Lomonosov Ridge, a feature that forms a prominent backbone for the deeper Arctic Ocean (Fig. 1).

Thirteen correlatable lithostratigraphic units are recognized in cores recovered from the central Artic Ocean. The stratigraphic units range in age from late Miocene to Holocene and can be correlated over several hundred thousand square kilometers. Six intervals of increased glacial ice-rafting are defined. A classification of glacial-marine sediment based on silt-clay histograms characterizes 4 classes. This is compared to non-Arctic glacial-marine sediment. (Author)

Spiral and meander foraging traces in the deep sea are not distributed in proportion to assumed food availability. Data collected by means of deep-sea photography failed to reveal a bathymetric gradient in behavioral complexity or sensitivity. The foraging paradigm developed by numerous trace fossil studies does not adequately predict the modern environment.

Fifteen lithostratigraphic units are present and correctable in 48 sediment cores recovered from the eastern flank of the Alpha Cordillera, central Arctic Ocean, The lithostratigraphy has been designated to facilitate correlation with established units of the central portion of the Amerasian Basin. Based on the extrapolation and interpolation of sedimentation rates from paleomagnetic reversals, calculated ages indicate a stratigraphic section ranging from early Pliocene to Holocene. The oldest sediment recovered yielded an age of 3.54 m. y.

The best Late Devonian configuration for the present Atlantic borderland area includes North America and northern Europe in contact or close proximity and a “proto-Atlantic Ocean” separating these continents from Africa and South America. During the Carboniferous, the Africa-South America block approached the North America-northern Europe block, destroying the “proto-Atlantic” and during the Permo-Triassic, there was no major separation of a tenuously fused South America, Africa, North America, Europe continent. By Late Triassic, the present North Atlantic began forming as the European and African continents began the shift to their present positions. The relationship of this continental movement to conodont biostratigraphy on either side of the present Atlantic Basin can be compared using the similarity index, 2w/ a + b, for conodont form-species. Conodont similarity between Europe and North America was greatest during the Late Devonian and Permian, with a gradual decrease in the Triassic that might be related to formation of the present Atlantic Basin. Similarity indices among other Atlantic borderland continents are somewhat ambiguous, as far as documenting continental proximity. This is because of limited taxonomic data. Also, such things as low Carboniferous Atlantic borderland conodont similarity may be explained by other factors such as the ecologic idiosyncrasies of the ancient Pacific and Tethyan water masses, or different continental elevations during the time interval. Regardless, some 100 conodont zones (43 Devonian, 23 Carboniferous, 12 Permian, 22 Triassic) provide an important biostratigraphic framework for the Atlantic borderlands. A calculated zonal similarity index mimics that of the form-species index. The greatest zonal similarity is during the Late Devonian, much less during the Carboniferous, but high again in the Triassic before dropping in the Late Triassic, perhaps, in part, reflecting Late Triassic separation of North America and Europe.

A Late Cretaceous (probably Maestrichtian) silicoflagellate assemblage has been recovered for the first time from the middle section of a core taken from the Alpha Cordillera in the central Arctic Ocean. The finding of Globigerina pachyderma in the top and very rarely in the bottom part of the core suggests a faulting or slumping process in the area.

The Lower Triassic rocks of the eastern Great Basin provide a record of the last marine deposition in the Cordilleran miogeosyncline. Sections are present in eastern Nevada, particularly in Elko County, and in the northwestern Utah. Most of the eastern Great Basin sections can be divided into (1) a lower shaly limestone, (2) the Meekoceras limestone zone, (3) an upper shaly limestone, and (4) an upper thick-bedded limestone. Thicknesses range from 700 to 3,000 feet. Redbeds are present only in the lower part of the western Utah sections and above the uppermost Triassic limestones near Currie. The Meekoceras zone contains many ammonoids, nautiloids, and conodonts. Pelecypods, gastropods, brachiopods, echinoderms, crinoids, foraminifers, and fish remains occur in beds above the Meekoceras interval. The Triassic rests unconformably on Permian rocks throughout the area of study, but no angular discordance was noted. The uppermost Triassic beds are overlain by Tertiary or Recent material. Age determination for the Triassic sections is based on the fossils of the Meekoceras zone which occurs near the base and represents middle Scythic of the European standard. Correlation with adjacent sections in Idaho, Utah, and western Nevada indicates that equivalents of additional Lower Triassic zones are probably present in the eastern Great Basin. Clastics above marine limestone in the Currie area may be Middle Triassic. Names for stratigraphic units have been established in adjacent areas. The Candelaria, Tobin, China Mountain, and Dixie Valley formations of western Nevada and the Moenkopi, Dinwoody, and Thaynes formations of Utah and Idaho can be correlated with the eastern Great Basin Triassic. Early Triassic seas invaded the northeastern Great Basin from Idaho and transgressed Nevada from east to west. Marine connections with the eugeosynclinal part were probably through California into southern Nevada. As the rate of subsidence varied in the miogeosyncline, marine tongues extended over the more stable craton toward the east. Seas were not uniformly present over western Utah and eastern Nevada and in northeastern Nevada a high area shed coarse detritus into the Lower Triassic sea. Redbeds accumulated in western Utah during early Triassic time; the source for this material was probably the "Nye-Lincoln" geanticline, which extended from southern California to the vicinity of Ely, Nevada. During the Middle Triassic, this feature was widened and fused to the craton, occupying t e position of the former geosyncline.

In a basin with an ~10 million sq km area, the number of sediment cores taken is of the magnitude of 1/10,000 sq km, and most cores are 300 cores from the T-3 drift is outlined; procedures are noted, as is the good record of the most recent major reversal of the earth's magnetic field left in 2-1/2 m (or longer) cores and of more magnetic events in cores longer than 3 m; this provides a basis for magnetic stratigraphic correlations with other parts of the world and determination of sedimentation rates. Progress in moisture content measurements, gross mineralogy, carbonate content and texture of the sediments and study of foraminifera and ice-rafted debris in sediments are still tenuous; the only sustained trend noted was toward less sinistral coiling specimens at the tops of cores which has been interpreted as indicating an ice-covered Arctic during most of the Pleistocene.

Sediments of 16 short cores taken as part of the Lomonosov Ridge Experiment (LOREX) can be organized into the first Pleistocene stratigraphy for the North Polar region. This stratigraphy can be correlated with stratigraphic units described from the Alpha-Chukchi areas, ∼300 km distant. The LOREX cores include at least 12 sedimentary subunits differentiated by texture, color, and carbonate content. The units are silty and arenaceous lutites and are principally glacial-marine. Benthic and planktonic foraminifera, degree of bioturbation, and Fe-Mn micro-nodule abundance generally are positively correlated. Foraminifera in core B-8, from 3,956 m in the Makarov Basin, may have been affected by CCD fluctuations that did not affect fossils in core B-24, from 1,600 m on the crest of the Lomonosov Ridge. The 12 stratigraphic units were deposited during the late Pleistocene and represent the same major sedimentary events as those of stratigraphic units K, L, and M of the Amerasian Basin. This correlation is excellent evidence for the remarkable and widespread uniform depositional style of glacial-marine sediment. Times of major glacial ice transport reflect deglaciation events in the central Arctic Ocean. Surface currents during deglaciation transport glacial ice in a more or less uniform pattern over at least 50% of the Arctic Ocean. Even thin sedimentary units deposited during relatively long time intervals are correlated over >500,000 km 2 .