Cretaceous Sea Level Rise

Down Memory Lane and the Road Ahead

Mu Ramkumar

• Publisher: Elsevier
• Year: 2015
• ISBN:
  9780128093238
• Topic: Naturwissenschaften
• Subtopic: Hydrologie

Cretaceous Sea Level Rise delves into the question of whether the observed short-term sea-level changes are regional (tectonic) or global (eustatic) and determines their possible relation to climate cycles; to assess the role of feedback mechanisms, i.e. thermal expansion/contraction of seawater, subsidence due to loading by water, changing vegetation of the Earth System and to investigate the relation of sea-level highs and lows to ocean anoxia and oxidation events, represented by black shales and oceanic red beds, and to evaluate the evidence for ephemeral glacial episodes or other climate events.

Though research has been, and is being, conducted in these fields since the introduction of sea level cycles and sequence development concepts in the 1970"s, the available information is scattered. Cretaceous Sea Level Rise presents the current understanding and future directions of the research on Cretaceous sea level cycles in a single source, forming a reference work for beginners, graduates and postgraduates who are interested in this subject.

• Authored by an expert in Sea Level Rise, with over 15 years' experience
• Concludes with a section that looks to the future of sea level change
• The only source to combine the current understanding and future directions of the research on Cretaceous sea level cycles in one place

Chapter 1

Introduction

Abstract

The recent enhanced awareness on the sea level rise as a response to natural and anthropogenic causes has emphasized the importance of understanding sea level fluctuations of the past especially that of the Cretaceous Period. The Cretaceous Period, a time known for extended duration of warmest periods of Earth’s history, provides an approximate corollary for understanding the possible impacts of ongoing global warming. The sequence stratigraphic concept was introduced given cognizance to the predominant role of the eustatic sea level fluctuations over the stratal patterns and the facies distribution, as observable from seismic coastal onlap/offlap charts. The studies that followed since then from a variety of geological and geographic settings have established that the sedimentary system responded to cyclicities of varying durations from few tens of million years to few thousand years. This chapter outlines the developmental history of the study of past sea level fluctuations, which was augmented with the introduction of sequence stratigraphy in the late 1970s and on the studies that followed since then.

Keywords

Global warming; sea level rise; Cretaceous Period; Sequence stratigraphy; controls of sedimentary systems

The modern sea level rise, which commenced 21,000 years ago, may continue for about another 40,000 years, should the natural process is allowed to continue, under the influence of shape of Earth’s orbit. However, the advent of modern human species, and the technological prowess the species learned to unleash to the detriment of the earth processes have interfered significantly to change the cyclic process of global ice volume changes and attendant environmental and climatic conditions. The introductory note of the UNESCO IGCP-609 Climate-environmental deteriorations during greenhouse phases: Causes and consequences of short-term Cretaceous sea level changes, states that “the recent rise in sea level in response to increasing levels of atmospheric greenhouse gases and the associated global warming is a primary concern for the society. Evidence from the Earth’s history indicates that the glacial-interglacial and other ancient sea level changes occurred at rates an order of magnitude or higher than that observed at present. To predict future sea levels, we need a better understanding of the record of past sea level change”. The Late Cretaceous has been a target of intensive study for past climatic and sea level fluctuations, due to excellent preservation of both oceanic and epicontinental strata, development of detailed biostratigraphic, geochronologic, and sequence stratigraphic frameworks, and a series of global scale biogeochemical perturbations that record major disruptions in the Earth’s carbon cycle and climate (Joo and Sageman, 2014). The interaction between sea level and biodiversity is important on long-term as well as short-term time scales (Holland, 2012). Similarly, the majority of the most profound extinctions in the Earth’s history are in one way or another related to sea level changes (Hallam and Wignall, 1999). These changes are often abrupt and possibly related to the loss of ecospace (regressions) or anoxia (transgression). For all these reasons, accurate knowledge on the sea level is essential (Munnecke et al., 2010).

Cognizant on the control exercised by the eustatic sea level fluctuations over the stratal patterns and the facies distribution, the concept of global sea level changes was introduced. It provided an impetus for correlating stratigraphic records with their counterparts located elsewhere. The relative sea level cycles (Figure. 1.1), first published by Vail et al. (1977) and revised by Haq et al. (1987, 1988), espoused that the sedimentary sequences are produced principally under the influence of sea level cycles, durations of which vary between few tens of millions of years (first-order cycle) and few million years (third-order cycle). Successive studies have shown that distinct sedimentary sequences (though the use of the term “sequence” itself was found to be diverging and misleading–van Loon, 2000) could be traced to sea level cycles of up to infra seventh order (Nelson et al., 1985; Williams et al., 1988; Carter et al., 1991). Vail et al. (1977) stated that the sea level chart published by them is incomplete and cycles of varying order could be added as the studies on sedimentary sequences progress; so that, more complete chart could be constructed. The aim behind this statement was to incorporate sea level cycles at the Milankovitch scale, to which the response of the sedimentation system is proved beyond reasonable doubt (Carter et al., 1991). Hays et al. (1976) convincingly demonstrated that the climatic records were dominated by frequencies characteristic of variations in the Earth’s tilt, precession, and eccentricity relative to the Sun. In the years since, numerous studies have upheld the validity of the Milankovitch climatic cycles in terms of 100, 41, and 23 Ka orbital periods that influence or control variations in sea-floor spreading (Quilty, 1980), global ice volume, thermohaline circulation, continental aridity and run off, sea surface temperature, deep ocean carbonate preservation, and atmospheric CO₂ and methane concentrations (Raymo et al., 1997). Cyclic sedimentation has been documented in numerous sedimentary basins and there are many lines of evidences that relate those cycles to short-term (Milankovitch band) glacioeustatic pulses (Laferriere et al., 1987; Grammer et al., 1996; Gale et al., 2002). Park and Oglesby (1991) are of the opinion that the Cretaceous deposits are characterized by cyclic deposition of carbonates with periodicities similar to the Milankovitch band. While examining the compiled data on the sediment volumes (mass) or sediment fluxes of the continental and marine subsystems to determine the complete routing in terms of mass conservation for specific time periods since the Late Glacial Maximum as well as the Cenozoic, Hinderer (2012) reported that the response times of the large sedimentary systems are within the Milankovitch band. Hilgen et al. (2014) opined that despite fragmentary sedimentation, stratigraphic continuity as revealed by cyclostratigraphy unequivocally supports the dominant role of depositional processes at the Milankovitch scale. On the contrary, Immenhauser (2005) stated that it is generally assumed that the effects of tectonism, sediment accumulation and compaction, and eustasy on the accommodation change cannot be untangled on a regional scale. In the time domain of few Ma and less, global cycle correlation is often unreliable and the effects of isostasy on the sea level show strong provincial variations. In contrast, on a regional scale, cycle correlation is more precise and regional tectonism has predictable limitations.

Figure 1.1 Eustatic sea level curve which came to be known as Vail/Exxon curve.
The morphology, causes of sudden sea level changes and the advocacy of using this curve for chronostratigraphic determination of strata were severely criticized by the scientific community, though, the concepts of shoreline shift as a result of tectonics, relative sea level fluctuation, climate and sediment flux were accepted, albeit reluctantly and with skeptism. See Miall (1991) and Miall and Miall (2001) for a detailed review on this debate. See Miall (2009), Catuneanu (2006), and Catuneanu et al. (2011) for current understanding and prevailing consensus. Source: Modified from Vail et al. (1977).

The relative sea level chart based on the seismic stratigraphic studies at Exxon, first presented by Vail et al. (1977) and later revised by Haq et al. (1987, 1988), recognized about 100 global sea level changes. Mitchum and Van Wagoner (1991) reported that a hierarchy of interpreted eustatic cyclicity in siliciclastic sedimentary rocks has a pattern of superposed cycles with frequencies in the ranges of 9–10, 1–2, 0.1–0.2, and 0.01–0.02 Ma (second- through fifth-order cyclicity, respectively). While examining the δ¹⁸O of Phanerozoic seawater, Veizer et al. (1997) observed the presence of high-frequency cycles within first-order cycle. Strauss (1997) recorded fourth-order cycles of sulfur isotope that stacked up to form third-order cycle fluctuations that in turn were accommodated within second-order cycles. Goldhammer et al. (1991) showed that the sequences of Paradox Basin exhibited a distinct cyclicity characterized by a hierarchical stacking pattern such that fifth-order shallowing upward cycles group into fourth-order cycles, which in turn stack vertically into part of a third-order cycle. McGhee (1992) and Gjelberg and Steel (1995) observed high-frequency sea level changes within a major sea level cycle. A detailed study of the Great Limestone Cyclothem of the northern Pennines (Alston Block) by Tucker et al. (2009) revealed that within the transgressive carbonates, the beds, averaging 75 cm in thickness and defined by millimeter-shale partings or centimeter-mudrock layers, form two thinning-upward to thickening-upward bed-sets. Oxygen isotope and strontium trace element data also revealed patterns of increasing and decreasing values through the limestone, which broadly correspond to the bed-thickness cycles. The beds are interpreted as millennial-scale cycles, the result of high-frequency, arid–humid climatic fluctuations. The bed-sets are interpreted as the response to a longer term arid–humid climate and sea level cycle, driven by the precession rhythm. Strasser et al. (1999) studied the Oxfordian and Berriasian sections representing shallow-water, carbonate-dominated sedimentary systems in the Swiss and French Jura, in Spain, and in Normandy. They all displayed a hierarchical stacking of depositional sequences. The superposition of high-frequency sea level changes on a long-term sea level trend led to repetition of diagnostic surfaces, defining sequence-boundary and maximum-flooding zones wherein the corresponding high-frequency surfaces are well developed. Chronostratigraphic tie points permitted estimation of the duration of large-scale sequences. This time control and the observed hierarchical stacking suggested that the high-frequency sea level changes were controlled by climatic cycles in the Milankovitch frequency band.

The stacking pattern of the cycles of sea level changes has not been questioned though consensus eludes on the causes and magnitudes of sea level variation (eg, Miller et al., 2003, 2004), absolute timings of these changes, and the utility of sea level charts for chronostratigraphy (Summerhayes, 1986; Hancock, 1993). Lack of consensus is such that, there is no established/accepted sea level chart across the K/Pg (Esmeray-Senlet et al., 2015), a boundary section that has been most intensively studied by the geoscientists! A much larger pattern (about 200 Ma) is interpreted as tectonically controlled eustasy probably related to the sea-floor spreading rates. Heller and Angevine (1985) suggested formation of Atlantic-type oceans with its attendant changes in the area/age distribution of the global ocean floor and the formation of extensional passive margins might be the primary reason for this first-order sea level changes and the role of oceanic floor spreading rate might be secondary. The sedimentary records of the Earth are the results of past tectonic and climatic events (Zhang et al., 2001; Armitage et al., 2011). As the sea level fluctuations are intimately coupled with climatic conditions and are often overprinted by tectonic evets, an ability/tool/method to accurately differentiate them is necessary.

From this review, it emerges that the history of sea level fluctuations was under the influences of myriad varieties of causes and varied durations. Though pragmatic estimates on the periodicities could be made, reliable and comparable stratigraphic records for authenticating such estimates are scarce or are limited to few time slices. As explained in following chapters, these well-constrained time slices and their stratigraphic records, despite being intensively studied, lack consensus on their sea level trends. With this background, in this book, an attempt is made to collate the available information on sea level fluctuations, causes, and the current understanding on the Cretaceous sea level cycles through extensive review of the classic and recent literat...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Acknowledgments
• Chapter 1. Introduction
• Chapter 2. Trends, Timings, and Magnitudes
• Chapter 3. Causes and Mechanisms
• Chapter 4. Methods, Tools and Techniques
• Chapter 5. Where It Stands and Where Is It Headed
• References
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