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New stable carbon isotope data (δ13Ccarb and δ18Ocarb) from the Lower–Middle Ordovician is presented from petroleum exploration well Olympic 1 in the Canning Basin, Western Australia. Olympic 1 continuously cored 319.53 m of sedimentary strata, from the basal part of the Willara Formation through the majority of the Nambeet Formation. This cored section comprises carbonate and siliciclastic deposits that constitute the primary fill sequence of the Canning Basin. Previous studies report CA-IDTIMS dates between 479.37 ± 0.16 Ma and 470.18 ± 0.13 Ma from bentonite beds within the Nambeet Formation and lower Willara Formation in Olympic 1. Four conodont biozones ranging from the Paroistodus proteus conodont Biozone (upper Tremadocian) to the Jumudontus gananda Biozone (upper Floian to lower Dapingian) have been identified from the same interval. The new carbon isotope data from the Olympic 1 core are superimposed on this robust framework to provide context for Tremadocian to Dapingian stable isotope trends for Australia. Three positive δ13Ccarb excursions are identified in the Olympic 1 δ13Ccarb isotope curve, which are correlated to the global generalized δ13C curve. The highest of these occurs in the basal Willara Formation, immediately above a CA-IDTIMS radioisotopic date of 470.18 ± 0.13 Ma within the upper Floian to lower Dapingian J. gananda conodont Biozone. The second falls in the upper Nambeet Formation, immediately above a middle Floian CA-IDTIMS radioisotopic date of 472.82 ± 0.13 Ma, and within the Oepikodus communis conodont Biozone. The oldest positive excursion occurs in the lower Nambeet Formation, immediately above a CA-IDTIMS radioisotopic date of 479.37 ± 0.16 Ma, and within the upper Tremadocian P. proteus conodont Biozone. Correlation of the Olympic 1 δ13Ccarb curve to Lower-Middle Ordovician δ13Ccarb curves from the Great Basin USA, Argentine Precordillera, Western Newfoundland and South China confirms the global distribution of dissolved inorganic carbon preserved in the geological record. This integrated record may be a useful reference for constraining the timing of major oceanographic events, and a key to establishing better links between the sedimentary successions of Western Australia and the larger Ordovician world.

New and published data are integrated herein to resolve the age and stratigraphic relationships for problematic strata of the Aeronian and Telychian (Llandovery; Silurian) in Ohio and Kentucky (USA). At least two major depositional sequences were traced along the eastern flank of the Cincinnati Arch; these are separated by a regionally angular unconformity with complex topography. Underlying units are progressively truncated to the northwest while overlying strata change facies, condense, and onlap in the same direction. The basal unit of the upper sequence is the Waco Member of the Alger Shale Formation in Kentucky and southern Ohio and the Dayton Formation in western Ohio. A persistent, positive carbonate carbon isotope (δ13Ccarb) excursion associated with the mid-Telychian Valgu Event is recognized in the upper subunit of the Waco Member; the absence of a comparable signal in the Dayton Formation corroborates interpretations that it is significantly younger. The correlations proposed here can be used to understand the nuanced depositional history and chronostratigraphic completeness of the lower Silurian in eastern North America. This framework can be used to characterize sea-level history and local conditions that prevailed during global paleoenvironmental events.

Constraining the age of strata is a fundamental source of uncertainty in the study of sedimentary rocks, particularly in restricted basins that generally lack index fossils. An illustrative example of this is the evaporite-bearing Salina Group in the Michigan Basin. Our integrated study of facies, paleontology, and stable isotope geochemistry from the base of the Salina Group in Wisconsin addresses long-standing chronostratigraphic uncertainty surrounding these units. Conodont samples from the basal boundary interval (Racine-Waubakee formation contact) produced non-diagnostic ‘disaster’ and ‘recovery’ faunas typical of both the Mulde (Homerian) and Lau (Ludfordian) events. Strontium isotope analysis (87Sr/86Sr) of these conodonts from five horizons just below the boundary yield values between 0.70844 and 0.70850 confirming a Homerian age. Multiple carbon isotope profiles through this interval confirm the presence of a 2.5–3‰ positive excursion. Cumulatively these data constrain the base of the Salina Group in Wisconsin to the Mulde Excursion interval (late Homerian). This integrated study provides a sound initial step towards a deeper understanding of the processes of Silurian evaporite formation in the Michigan Basin.

New and published stratigraphic data are integrated herein to resolve the age and depositional setting of Middle Devonian strata in the Gobi-Altai Terrane of south-central Mongolia (Bayanhongar Province). The Tsagaankhaalga Formation (Emsian?–Eifelian) is composed primarily of tabular sandy carbonates; it is sharply overlain by dark, fine-grained volcanoclastic marine sedimentary rock of the Govialtai Formation (Givetian), which is comparatively unfossiliferous, except for sporadic, fossiliferous carbonate interbeds. The latter unit contains abundant tentaculites as well as a newly recovered collection of conodonts assigned to the lower Givetian varcus Zone ( timorensis , rhenana , or ansatus ). A positive shift in bulk magnetic susceptibility coincides with the Tsagaankhaalga/Govialtai contact, and elevated values within the Govialtai correspond to tuffaceous and rhyolitic strata. The transition from carbonate facies of the Tsagaankhaalga Formation to the volcanoclastic shales of the Govialtai Formation is interpreted as the result of local tectonic activity. This may be qualitatively described as a transition from a shallow marine carbonate shoal with an epibenthic fauna (Tsagaankhaalga), to a deeper, clastic dominated environment with a nektic fauna (Govialtai). The pulse of tectonism must predate the lower Givetian, and it echoes the “Tsakhir Event”, which is recorded by the transition from Ordovician–Silurian carbonates to Lochkovian conglomerate. These findings provide useful biostratigraphic control and insight into the complex tectonic evolution of the Gobi-Altai Terrane and adjacent blocks on the Eurasian Craton.

New stable isotope data from organic carbon (δ13Corg) and inorganic elemental geochemistry data have been generated from Upper Ordovician to Silurian strata in two boreholes in the Lublin Basin of Poland: Grabowiec-6 and Zwierzyniec-1. They have been integrated here with biostratigraphical data from graptolites, acritarchs, and chitinozoans. Faunal assemblages from Grabowiec-6 indicate that it spans from the Katian (clingani graptolite Biozone) to the Gorstian (scanicus graptolite Biozone); δ13Corg values from this section record the Sheinwoodian Ireviken Excursion, the Homerian Mulde Excursion, and a minor positive shift associated with the lower Ludfordian leintwardinensis Biozone. The second section, Zwierzyniec-1, spans the Sandbian through Gorstian (nilssoni Biozone); δ13Corg values record the Hirnantian carbon isotope excursion (HICE) and the Ireviken Excursion as well.Elemental geochemistry data is used to recognize subtle changes in provenance and lithology. Significant increases in the abundance of V and Mo are recognized in strata deposited above the Ireviken Excursion. The enrichment of these redox sensitive elements suggests that persistent regional anoxia and euxinia may be associated with the aftermath of these oceanographic disturbances. Some of these same trace elements, along with Fe2O3, and Pb are also abundant in strata coeval with, or just below the Ireviken and HICE excursions. This may have a causal link with malformed palynomorphs observed at these intervals by some workers, which are thought to reflect toxic levels of dissolved heavy metals in the world's oceans.

New and published stratigraphic data are integrated herein to resolve the age and correlation of the Waco Member (Alger Shale Formation), a problematic Telychian lithostratigraphic unit exposed in east-central Kentucky (United States). This interval is correlated with strata presently assigned to the Dayton Member of the Drowning Creek Formation in south-central Ohio and north-central Kentucky, where recent conodont studies refer these beds to the Pterospathodus eopennatus Superzone, a conclusion that is reinforced by an interval of elevated stable carbon isotope (δ13C) values, consistent with the lower Telychian “Valgu” Excursion. This correlation is strengthened by observations of facies and new carbonate carbon isotope (δ13Ccarb) data generated from localities in south-central Ohio and, for the first time in publication, from the type area of the Waco in east-central Kentucky. It is now clear that both lithostratigraphic units are substantially older than the recently redefined Dayton Formation of west...