Mike Fuller

Sea Level and Astronomically Induced Environmental Changes in Middle and Late Eocene Sediments from the East Tasman Plateau

Eocene sediments drilled at the East Tasman Plateau (ETP) exhibit well-defined cycles, high-resolution magnetic stratigraphy, and environmentally-controlled dinoflagellate and diatom distribution patterns. We derive a cyclostratigraphy from the spectral analysis of high-resolution elemental concentration records (Ca, Fe) for this shallow marine time series spanning the middle to early late Eocene (C16n.2n - C21). Changes in carbonate content, the ratio between Gonyaulacoid and Peridinioid dinocysts, and relative abundance of oligotrophic diatoms serve as proxies for a high-resolution climatic and sea-level history with high values representing high sea-level stands and decreased eutrophy of surface waters. Changing ratios between high latitude dinocysts versus cosmopolitan species provide clues on sea surface temperature trends and water mass exchange. Our results show that the relatively shallow-water middle Eocene environments of the ETP are influenced by orbitally-forced climatic cycles superimposed on third order relative sea-level changes. Changes in the dominance of Milankovitch frequency at ∼38.6 Ma (late Eocene) is related to an initial deepening-step within the Tasmanian Gateway prior to the major deepening during the middle late Eocene (∼35.5 Ma). Decreasing sedimentation rates at 38 Ma and 37.2 Ma reflect winnowing associated with sea-level fall. This episode is followed by renewed transgression. Dinocyst distribution patterns indicate high latitude, probably cool temperate surface water conditions throughout, with the exception of a sudden surge in cosmopolitan species near the base of subchron C18.2r, at ∼41 Ma; this event is tentatively correlated to the Middle Eocene Climatic Optimum.

Lunar and Earth Sciences at the Time of the Apollo Landings

We will now focus in on the moon itself in particular on the origin of its surface features. If they are indeed giant impact craters they might account for lunar magnetism. We will also introduce the topic of paleomagnetism some other relevant ideas from mid 20th century geophysics and geochemistry which are key to our story.

The Moon in Antiquity and in the Development of Modern Science

To begin our journey to understand the puzzle of lunar magnetism, we first look at the long history of the development of our understanding of the earth moon system to set the stage for Apollo.

Impact Related Shock on the Lunar Surface and the Lunar Paleomagnetic Record

The work of Baldwin and others discussed in Chap. 2 had shown that the craters and basins of the moon were the result of giant impacts, which must have generated large shock waves over considerable volumes. Could these shock effects, or possible magnetic fields generated in the events, explain the remanent magnetism (NRM) of the lunar samples?

Lunar Paleomagnetism: Methods and Preliminaries

The lunar samples were collected from the regolith, having been brought there by impacts that excavated them from their previous locations. The orientation in which they originally formed is therefore unknown. Thus tests of the reliability of their record depending upon planetary wide consistencies of paleomagnetic directions cannot be used, as they are on earth. Our approach has been to use internal consistencies within samples and demagnetization characteristics, which serve as fingerprints for particular types of remanent magnetization.

Apollo: Getting to the Moon

The Apollo program was preceded by Mercury (1961–1963), Gemini (1964–1965), and by the Russian, Vostok (1961–1963) and Voshkod (1964–1965) Soyuz (1967–) programs.

The Earth’s Magnetism: Paleomagnetism as a Rosetta Stone for Earth History

Paleomagnetism, the record of the geomagnetic field carried by rocks, has played a key role in our understanding of Earth. In this chapter, we review the history of our understanding of the Earth’s magnetic field and its paleomagnetic record, as an indication of what the possible record of a lunar field might yield. We also begin to consider the ubiquitous magnetic fields in the cosmos and how they are generated and maintained.

Advances in Lunar Science with Apollo

In this chapter we review the results from the Apollo missions. With the availability of the samples, we immediately saw that they consisted of basalts, similar to those on earth, and breccias, which were the result of impacts. We also came face to face with the puzzle of lunar magnetism. Not only did the samples carry remanent magnetization (NRM), but surface magnetometers showed that there were fields at the various sites far larger than predicted by the earlier satellite measurements. Finally magnetometers on sub-satellites revealed that large regions of the lunar crust were magnetized. Yet there was no active lunar dynamo field at present. How did this magnetization arise?

Lunar Paleomagnetism and the Case for an Early Lunar Dynamo

Criteria for reliability of the lunar NRM are established and the test of the case for an early dynamo described. The history of the intensity of ancient lunar fields from the samples is the key observation we need and unfortunately even more difficult than determining paleomagnetic direction reliably, but progress has been made. The results from the samples are tested against the record from the lunar crustal magnetic anomalies.

The Birth of the Space Age and Unmanned Missions to the Moon

After Sputnik and prior to manned flight, the Luna, and Explorer programs had taught us about the magnetic environment of the Earth with its Van Allen Radiation Belts, and shown that the moon unlike the earth had no detectable magnetic field. The Surveyor missions demonstrated that the Moon was an evolved body like Earth rather than a primitive body, so it looked as though there could be a core, in which a magnetic field might at one time have originated.