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Summary: New dates and analysis of 12 deep and 57 shallow cores allow a more detailed interpretation of the Pleistocene shelf edge of the Florida Platform as found in various facies of the Key Largo Limestone beneath the Florida Keys. In this study a three-phase evolution of the Quaternary units (Q1–Q5) of the Key Largo is presented with new subdivision of the Q5. (1) In the first phase, the Q1 and Q2 (perhaps deposited during oxygen-isotope stage 11) deep-water quartz-rich environment evolved into a shallow carbonate phase, (2) Subsequently, a Q3 (presumably corresponding to oxygen-isotope stage 9) flourishing reef and productive high-platform sediment phase developed. (3) Finally, a Q4 and Q5 (corresponding to oxygen-isotope stages 7 and 5) stabilization phase occurred with reefs and leeward productive lagoons, followed by lower sea levels presenting a sequence of younger (isotope substages 5c, 5a) shelf-margin wedges, sediment veneers and outlier reefs. The Key largo Limestone provides an accessible model of a carbonate shelf edge with fluctuating water depth, bordering a deep seaward basin for a period of at least 300 ka. During this time, at least four onlaps/offlaps, often separated by periods of karst development with associated diagenetic alterations, took place. The story presented by this limestone not only allows a better understanding of the history of south Florida but also aids in the interpretation of similar persistent shelf-edge sites bordering deep basins in other areas.

Speleothems from Oregon Caves National Monument, a dissolutional cave system located in the Klamath Mountains of southwest Oregon, are composed mainly (>90%) of columnar calcite crystals. Columnar calcites form through syndepositional lateral coalescence of crystallites and precipitate under stable hydrodynamic conditions in humid, temperate climates. Numerous discontinuities from short-lived events (<100 years) punctuate the calcites. Minor fabrics, such as transitional- and randomly-oriented elongate calcites are seeded on these discontinuities and detrital layers. Columnar calcites eventually overrun sub-horizontally oriented crystals as a result of competitive growth. Large (≈750 μm) crystal terminations indicate growth under increased water film resulting from greater flow and/or ponding. 14 Useries dates provide mean growth rates of 5.6 to 27.9 mm/ka during interglacial periods (marine isotope stages 11 through 9, substage 5e, and late stage 2 through stage 1), and indicate short growth intervals during early-to mid-interglacial periods. Several outcrop-scale discontinuities represent periods of prolonged growth stoppage. Growth cessation occurred during the colder phases of stages 8–9 and 6–7, which translate into hiatuses of 77.5 and 99 ka respectively. Given the sensitivity of alpine regions to climate change and the lack of evidence for continental or alpine glaciation, the hiatuses are presumed to be caused by groundwater freezing during extended periglacial conditions, triggered by the lowering of periglacial thresholds by as much as 1800 m during glacial periods.

A stalagmite from Rana, northern Norway, dated by the TIMS uranium-series technique, yields records of stable oxygen and carbon isotopes covering the period from late marine oxygen isotope substages (MIS) 5e to 5a, that is, 123,350 to 73,300 yr ago. Rapid growth (∼46 μm/yr) between 123,350 and 119,500 yr ago reflects climatic conditions favorable for speleothem growth. This period is characterized by century- to millennial-scale oscillations in both stable isotope records, where both the absolute values and the isotope ranges are similar to Holocene and older samples from the region. From 119,500 to 107,700 yr ago, speleothem growth was slow (∼0.7 μm/yr), and between 107,700 and 73,300 yr ago growth is barely noticeable (0.07 μm/yr). During the period of slow growth the stable isotope records show an overall enrichment trend. The transition between rapid and slow growth rate occurring sometime between 119,500 and 107,700 yr ago is believed to reflect the termination of interglacial climate in this region. The absence of detritus and corrosion features in the slowly deposited calcite suggests that the valley outside the cave remained sufficiently ice free for speleothem growth to occur until at least 73,300 yr ago.

Late Quaternay pipe- or well-like paleokarst features are being exhumed and modified by modern coastal processes along the north-western and northern coasts of Puerto Rico. These features are cigar-shaped tubes dissolved into host rock, with depths up to 4 m, and widths of ≈0.5 m. They can be so densely packed that much of the original deposit has been removed. Most contain evidence of a few millimeters thick calcrete lining, consisiting of micrite laminae, and a zone of indurated rock up to several centimeters thick of micrite and microspar. Many pipes are filled with insoluble material similar in appearance to the insolubles of the host rock but more concentrated, and augmented by material which resemble terra-rossa. At one site the pipes have retained this primary fill material, now somewhat cemented. At the other site the primary fill material, probably sand rather than terra-rossa, was completely removed, the pipes re-filled with marine debris and the whole complex cemented. Some pipes show more than one cycle of filling, emptying and re-filling, and some areas show more than one phase of pipe formation.

We used Sr/Ca and stable isotope data from well dated and preserved corals from the northeastern Caribbean to determine the seasonal environmental conditions for four continuous years during the Eemian, the last time the Earth was in a prolonged warm phase. We determined that the seasonal range in SST during the Eemian was 25°–30° C. This is ∼1–2° larger than at present and caused primarily by winter cooling and, only to a small degree, by summer warming. As climate modeling studies indicate, the bias towards colder winters can be explained by changes in low latitude insolation induced by altered orbital parameters, modulated by atmospheric CO2levels that were lower than today. Milankovitch forcing at higher latitudes was probably less important.