Samuel Epstein

Revised carbonate-water isotopic temperature scale

The relationship between temperature and O^(18) content relative to that for a Cretaceous belemnite of the Pee Dee formation previously reported (Epstein, Buchsbaum, Lowenstam, and Urey, 1951) has been re-determined using modified procedures for removing organic matter from shells, and is found to be nt(°C) = 16.5 - 4.3δ + 0.14δ^2 nwhere δ is the difference in per mil of the O^(18) to O^(16) ratio between the sample and reference gas. The new relationship agrees with that determined by McCrea (1950) for inorganically precipitated calcium carbonate. Carbonate-carbon dioxide exchange experiments were done to determine the direct and indirect effects of organic matter in the shell on the mass spectrometer analyses.

MEASUREMENT OF PALEOTEMPERATURES AND TEMPERATURES OF THE UPPER CRETACEOUS OF ENGLAND, DENMARK, AND THE SOUTHEASTERN UNITED STATES

Since the abundance of the O 18 isotope in calcium carbonate varies with the temperature at which it is deposited from water, the variation in abundance can be used as a thermometer. This paper discusses the following problems: (1) the magnitude of the effect expected, (2) the mass spectrometer of high sensitivity, (3) the preservation of the record during geological time, (4) the constancy of the isotopic composition of the ocean, (5) the impossibility of using skeletons of air breathing animals, and (6) the temperature of marine animals relative to their surroundings. A Jurassic belemnite is used to show that the record has been retained since Jurassic times, and belemnites of the Upper Cretaceous of the United States, England, and Denmark are used to determine the temperature of this time at these localities. The temperatures are about 15°–16°C and indicate nearly uniform temperature over this latitudinal belt. Because of the possible variation in O 18 content of the oceans and the limited number of samples, these temperatures are regarded as preliminary.

The oxygen and hydrogen isotope geochemistry of clay minerals

Abstract Oxygen and hydrogen isotope analyses have been made on a variety of clay minerals of sedimentary and diagenetic origins. The interlayer water of clay minerals was found to exchange rapidly with atmospheric water. Conditions under which the interlayer water could be removed from the clays without affecting the isotopic compositions of their aluminosilicate oxygen and hydrogen were therefore determined, and the interlayer water was routinely removed and discarded prior to isotopic analysis. Approximate fractionation factors for clay mineral-water systems at sedimentary temperatures, inferred from the isotopic compositions of natural samples, are: α Oxygen min - H 2 O α Hydrogen min - H 2 O Montmorillonite 1.027 0.94 Kaolinite 1.027 0.97 Glauconite 1.026 0.93 Consistency of a relationship between oxygen and hydrogen isotope ratios of kaolinites taken from a variety of areas and having different isotope ratios was demonstrated. This relationship results from exchange of clays with different meteoric waters under conditions in which the fractionation factors are relatively constant. This strongly suggests that the fractionation factors are equilibrium ones and that kaolinite forms in isotopic equilibrium with its environment. Deviations of the isotopic composition of montmorillonites from a similar relationship have been interpreted as resulting from isotopic exchange at slightly elevated temperatures. There was no clearly demonstrable case of clay minerals undergoing isotopic re-equilibration at sedimentary temperatures, although this is one possible interpretation of the data of some Upper Cretaceous glauconites.

CARBONATE-WATER ISOTOPIC TEMPERATURE SCALE

A relationship between temperature and relative O 18 abundance in calcium carbonate in marine shells has been determined. If the relative O 18 abundance of the water in which the shell grew is known, the temperature can be determined to an accuracy of ±1.0°C. The relative O 18 contents of marine waters increase with salinity and, in the case of surface marine waters, with salinity and temperature.

Hydrogen and oxygen isotope ratios in nodular and bedded cherts

Abstract Hydrogen and oxygen isotopic compositions of cherts (δD for hydroxyl hydrogen in the chert, δ 18 O for the total oxygen) have been determined for a suite of samples from the central and western United States. When plotted on a δD-δ 18 O diagram, Phanerozoic cherts define domains parallel to the meteoric water line which are different for different periods of geologic time. The elongation parallel to the meteoric water line suggests that meteoric waters were involved in the formation of many cherts. The existence of different chert δ-values for different geologic times indicates that once the granular microcrystalline quartz of cherts crystallizes its isotopic composition is preserved with time. An explanation for the change with time of the isotopic composition of cherts involving large changes with time in the isotopic composition of ocean water is unlikely since δ 18 O of the ocean would have had to decrease by about 3‰between Carboniferous and Triassic time and then increase about 5%.` from Triassic to Cretaceous time. Such isotopic changes cannot be accounted for by extensive glaciation, sedimentation of hydrous minerals, or input of water from the mantle into the oceans. The variation with time of the chert δ-values can be satisfactorily explained in terms of past climatic temperature fluctuations if the chert-water isotope fractionation with temperature is approximated by 1000 ln α = 3.09 × 10 6 T −2 – 3.29. Crystallization temperatures so inferred suggest that the average climatic temperatures for the central and western U.S. decreased from about 34 to 20°C through the Paleozoic, increased to 35–40°C in the Triassic, and then decreased through the Mesozoic to Tertiary values of about 17°C. A few data for the Precambrian suggest the possibility that Earth surface temperatures may have reached about 52°C at 1.3 b.y. and about 70°C at 3 b.y.

Paleotemperatures of the Post-Aptian Cretaceous as Determined by the Oxygen Isotope Method

A study of paleotemperatures of the post-Aptian Cretaceous, using the oxygen isotope method for measuring temperatures, is here reported. The investigation, an elaboration of the initial exploratory one reported earlier (Urey et al., 1951), was made by using belemnite guards, Inoceramus, brachiopod and oyster fragments, chalks, and bioclastic matrix materials. The samples were collected primarily from western European localities and from the southeastern part of the United States. A few samples were from Greenland, Japan, Australia, India, and Algeria. The results indicate a progressive rise in ocean temperatures from the Cenomanian, climaxing in the Coniacian-Santonian, followed by a general decline to the Maestrichtian. This climatic history is particularly evident from the many belemnite data and corroborated by the data for the other associated burial elements. The validity of temperatures measured by the use of various fossils is evaluated from the point of view of the preservation of original skeletal material and from considerations of what fraction of local temperature amplitude is recorded by different forms. The study also indicates that during the Coniacian-Santonian temperature climax, marginal subtropical ocean temperatures extended northward into the present-day cold-temperate belt, with this northward displacement decreasing toward Maestrichtian time. It appears from the belemnite data and from the paleogeographical distribution of belemnites in the post-Aptian Cretaceous that the belemnites became stenothermal following Albian times. A study of the temperatures recorded by the unusually well-preserved elements of the Maestrichtian Coon Creek assemblage from Tennessee permitted a comparison with the recorded temperatures of the present-day Bermuda biota. A parallelism between the temperatures recorded by these two faunal assemblages appears to be present.

On the Origin of Sedimentary Aragonite Needles of the Great Bahama Bank

Field evidence on the origin of sedimentary aragonite needles indicates that the needles may be derived from certain algal carbonates. Determinations were made of the relative

Climatic implications of the D/H ratio of hydrogen in C-H groups in tree cellulose

O^{18}