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James G. Ogg

Publications and source records attributed to James G. Ogg.

6 recordsLinked to original sources
USGS2023

Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA

Eocene transient global warming events (hyperthermals) can provide insight into a future warmer world. While much research has focused on the Paleocene–Eocene Thermal Maximum (PETM), hyperthermals of a smaller magnitude can be used to characterize climatic responses over different magnitudes of forcing. This study identifies two events, namely the Eocene Thermal Maximum 2 (ETM2 and H2), in shallow marine sediments of the Eocene-aged Salisbury Embayment of Maryland, based on magnetostratigraphy, calcareous nannofossil, and dinocyst biostratigraphy, as well as the recognition of negative stable carbon isotope excursions (CIEs) in biogenic calcite. We assess local environmental change in the Salisbury Embayment, utilizing clay mineralogy, marine palynology, δ 18 O of biogenic calcite, and biomarker paleothermometry (TEX 86 ). Paleotemperature proxies show broad agreement between surface water and bottom water temperature changes. However, the timing of the warming does not correspond to the CIE of the ETM2 as expected from other records, and the highest values are observed during H2, suggesting factors in addition to p CO 2 forcing have influenced temperature changes in the region. The ETM2 interval exhibits a shift in clay mineralogy from smectite-dominated facies to illite-rich facies, suggesting hydroclimatic changes but with a rather dampened weathering response relative to that of the PETM in the same region. Organic walled dinoflagellate cyst assemblages show large fluctuations throughout the studied section, none of which seem systematically related to CIE warming. These observations are contrary to the typical tight correspondence between climate change and assemblages across the PETM, regionally and globally, and ETM2 in the Arctic Ocean. The data do indicate very warm and (seasonally) stratified conditions, likely salinity-driven, across H2. The absence of evidence for strong perturbations in local hydrology and nutrient supply during ETM2 and H2, compared to the PETM, is consistent with the less extreme forcing and the warmer pre-event baseline, as well as the non-linear response in hydroclimates to greenhouse forcing.

Atlantic Coastal Plain↗
USGS2013

Sedimentary history of the Tethyan margins of eastern Gondwana during the Mesozoic

A composite Mesozoic geological history for the Gondwana margins to the Eastern Tethys Ocean can be assembled from stratigraphic successions on the Australian and Himalayan margins and from drill sites of Ocean Drilling Program Legs 122 and 123. During the Triassic, this region drifted northwards, entering tropical paleolatitudes during the Late Triassic-Early Jurassic, then returned to mid-latitudes for the Middle Jurassic through Early Cretaceous. Shallow-water carbonates are restricted to the tropical-latitude interval; at other times, the margins are dominated by clastic deposition. Episodes of deltaic sandstone progradation over the shelves are caused by eustatic sealevel fluctuations, by wet climatic conditions within the source regions and by local tectonic activity. A major hiatus between Callovian shallow-water shelf deposits and Oxfordian deep-water sediments is an ubiquitous feature, which may be related to a widespread plate tectonic reorganization and the cascading effects of associated sealevel rise and elevated carbon dioxide levels. Off Northwest Australia, this Callovian/Oxfordian event also coincides with an episode of block faulting. Marginal sediments deposited during the Late Jurassic are mainly marine claystone containing abundant terrigenous organic matter. Shallow depths of carbonate compensation (CCD) during the Late Jurassic through Early Cretaceous prevented the preservation of carbonate over most of the Argo basin off Northwest Australia, and these deep-sea sediments consist mainly of condensed, oxygenated radiolarian-rich claystone. During the late Kimmeridgian-early Tithonian, a downward excursion in the CCD enabled limited preservation of some larger nannofossils and mollusc fragments within the pelagic deposits, a feature also recorded in coeval deposits in the Atlantic. Explosive volcanism accompanied the final stages of rifting between India and Australia during the late Berriasian and Valanginian, producing volcaniclastic debris washing into the deltas and widespread ash deposits. The late Barremian and Aptian sediments indicate a rise in the CCD, accompanied by warming of the region and an increased delivery of organic-rich claystone into the basins.

Book chapter↗
USGS2006

An integrated chronostratigraphic data system for the twenty-first century

Research in stratigraphy is increasingly multidisciplinary and conducted by diverse research teams whose members can be widely separated. This developing distributed-research process, facilitated by the availability of the Internet, promises tremendous future benefits to researchers. However, its full potential is hindered by the absence of a development strategy for the necessary infrastructure. At a National Science Foundation workshop convened in November 2001, thirty quantitative stratigraphers and database specialists from both academia and industry met to discuss how best to integrate their respective chronostratigraphic databases. The main goal was to develop a strategy that would allow efficient distribution and integration of existing data relevant to the study of geologic time. Discussions concentrated on three major themes: database standards and compatibility, strategies and tools for information retrieval and analysis of all types of global and regional stratigraphic data, and future directions for database integration and centralization of currently distributed depositories. The result was a recommendation to establish an integrated chronostratigraphic database, to be called Chronos, which would facilitate greater efficiency in stratigraphic studies (http://www.chronos.org/) . The Chronos system will both provide greater ease of data gathering and allow for multidisciplinary synergies, functions of fundamental importance in a variety of research, including time scale construction, paleoenvironmental analysis, paleoclimatology and paleoceanography. Beyond scientific research, Chronos will also provide educational and societal benefits by providing an accessible source of information of general interest (e.g., mass extinctions) and concern (e.g., climatic change). The National Science Foundation has currently funded a three-year program for implementing Chronos.. ?? 2006 Geological Society of America. All rights reserved.

Special Paper of the Geological Society of America↗
USGS1997

The Blake Nose Cretaceous-Paleogene (Florida Atlantic margin, ODP Leg 171 B): An exemplar record of the Maastrichtian-Danian transition

During ODP Leg 171B, devoted to the analysis of the Blake Plateau margin in front of Florida, 16 holes have been drilled in 5 distinct sites. The sites have documented a sedimentary succession ranging in age from Aptian to Eocene. Emphasis has been put on critical periods, comprising the Paleocene-Eocene transition, the Cretaceous-Tertiary boundary which has been cored in excellent conditions, the middle Maastrichtian extinctions and the Albian anoxic episodes.

Comptes Rendus de l'Academie des Sciences - Serie ↗