Abstract: Petroleum exploration in the Gulf of Mexico relies on numerous calcareous nannofossil and foraminiferal bioevents to correlate between wells and provide age estimates for stratigraphic horizons. Micropaleontologists working in the Gulf of Mexico region have developed competing biozonations for the region, some of which include bioevents that do not have published absolute age estimates. New absolute age estimates are proposed for 41 foraminiferal and calcareous nannofossil bioevents in the offshore Miocene Gulf of Mexico, using the quantitative probabilistic biostratigraphic method of ranking and scaling (RASC) to analyze 721 wells from Paleo-Data’s proprietary biostratigraphic database. The relative ages obtained from an RASC analysis of the wells have been converted to absolute age estimates using cubic spline interpolation between selected bioevents with calibrated absolute ages. These new age estimates will increase biostratigraphic age resolution for the Miocene Gulf of Mexico and verify the ranking of bioevents regularly used in the Gulf of Mexico petroleum industry. The measured depths of events were also used to estimate regional rock accumulation rates for the Miocene Gulf of Mexico stratigraphic record.

Radiocarbon analyses of pollen, ostracodes, and total organic carbon (TOC) provide a reliable chronology for the sediments deposited in Bear Lake over the past 30,000 years. The differences in apparent age between TOC, pollen, and carbonate fractions are consistent and in accord with the origins of these fractions. Comparisons among different fractions indicate that pollen sample ages are the most reliable, at least for the past 15,000 years. The post-glacial radiocarbon data also agree with ages independently estimated from aspartic acid racemization in ostracodes. Ages in the red, siliclastic unit, inferred to be of last glacial age, appear to be several thousand years too old, probably because of a high proportion of reworked, refractory organic carbon in the pollen samples. Age-depth models for five piston cores and the Bear Lake drill core (BL00-1) were constructed by using two methods: quadratic equations and smooth cubic-spline fits. The two types of age models differ only in detail for individual cores, and each approach has its own advantages. Specific lithological horizons were dated in several cores and correlated among them, producing robust average ages for these horizons. The age of the correlated horizons in the red, siliclastic unit can be estimated from the age model for BL00-1, which is controlled by ages above and below the red, siliclastic unit. These ages were then transferred to the correlative horizons in the shorter piston cores, providing control for the sections of the age models in those cores in the red, siliclastic unit. These age models are the backbone for reconstructions of past environmental conditions in Bear Lake. In general, sedimentation rates in Bear Lake have been quite uniform, mostly between 0.3 and 0.8 mm yr ‒1 in the Holocene, and close to 0.5 mm yr ‒1 for the longer sedimentary record in the drill core from the deepest part of the lake.