Neogene sapropels in the Mediterranean: a review

Cramp, A.; O'Sullivan, Gerard M.

doi:10.1016/s0025-3227(98)00092-9

Cited by 225 publications

(86 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…One of the outstanding issues concerns the response of overturning circulation to increased freshwater flux to the sea surface. Such a response is thought evidenced by the regular intercalation of organic-rich sediments -sapropels -in the Neogene record of, in particular, the eastern Mediterranean basin (reviews of the extensive literature on this subject are given by Rohling, 1994;Cramp and O'Sullivan, 1999;Meyers, 2006;Emeis and Weissert, 2009). Sapropels coincide with precession-controlled climatic states Lourens et al, 1996) which are known to involve an increase of freshwater input to the Mediterranean sea (e.g., Tuenter et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

The response of Mediterranean thermohaline circulation to climate change: a minimal model

Meijer

Dijkstra

2009

Clim. Past

View full text Add to dashboard Cite

Abstract. Physics-based understanding of the effects of paleoclimate and paleogeography on the thermohaline circulation of the Mediterranean Sea requires an ocean model capable of long integrations and involving a minimum of assumptions about the atmospheric forcing. Here we examine the sensitivity of the deep circulation in the eastern Mediterranean basin to changes in atmospheric forcing, considered a key factor in the deposition of organic-rich sediments (sapropels). To this extent we explore the setup of an ocean general circulation model (MOMA) with realistic (present-day) bathymetry and highly idealized forcing. The model proves able to qualitatively capture some important features of the large-scale overturning circulation, in particular for the eastern basin. The response to (i) a reduction in the imposed meridional temperature gradient, or (ii) a reduction in net evaporation, proves to be non-linear and, under certain conditions, of transient nature. Consistent with previous model studies, but now based on a minimum of assumptions, we find that a reduction in net evaporation (such as due to an increase in freshwater input) may halt the deep overturning circulation. The ability to perform long model integrations allows us to add the insight that, in order to have the conditions favourable for sapropel formation persist, we must also assume that the vertical mixing of water properties was reduced. The "minimal" model here presented opens the way to experiments in which one truly follows the basin circulation into, or out of, the period of sapropel formation and where forcing conditions are continously adjusted to the precession cycle.

show abstract

Section: Introductionmentioning

confidence: 99%

The response of Mediterranean thermohaline circulation to climate change: a minimal model

Meijer

Dijkstra

2009

Clim. Past

View full text Add to dashboard Cite

show abstract

“…Orbitally driven intervals of increased precipitation over parts of Africa and increased river run-off are thought to be the main environmental changes leading to sapropel formation (Rossignol-Strick et al, 1982;Rossignol-Strick, 1985;Freydier et al, 2001). Several studies, using different proxies, have been carried out over the past 25 years in order to understand the mechanisms by which the basin reacts to climatic change and induces sapropel formation, with debate mainly concentrated on the role of deep-water anoxia and/or enhanced productivity in producing organic carbon rich levels (see De Lange et al, 1999;Cramp and O'Sullivan, 1999;Thomson et al, 1999, for synthesis).…”

Section: Introductionmentioning

confidence: 99%

Abnormal carbonate diagenesis in Holocene–late Pleistocene sapropel-associated sediments from the Eastern Mediterranean; evidence from Emiliania huxleyi coccolith morphology

Crudeli

Young

Erba

et al. 2004

Marine Micropaleontology

View full text Add to dashboard Cite

In studying the Holocene -late Pleistocene record of the Eastern Mediterranean, considerable Emiliania huxleyi size/shape variation not clearly assignable to primary or secondary calcification was observed. Accordingly, different morphotypes were distinguished by light microscope (LM).A subsequent scanning electron microscope (SEM) analysis of selected samples has indicated that Emiliania huxleyi coccoliths are variably affected by carbonate diagenesis in these sediments. A series of diagenetic stages were qualitatively defined, comprising well-preserved specimens, three overgrowth (OG1 to OG3) and one etching (E1) stage. Comparing SEM and LM observations, a tentative correlation between the E. huxleyi calcified LM-morphotypes and E. huxleyi SEM-overgrowth stages is proposed here.Our study not only indicates that Emiliania huxleyi coccoliths are strongly influenced by carbonate diagenesis, but also that they show effects of carbonate precipitation and dissolution much more clearly than other coccoliths. The relative abundances of the different LM-morphotypes were used to define an E. huxleyi overgrowth index (EXO) that qualitatively estimates carbonate precipitation/dissolution on coccoliths in this sediment. This resulted in definition of five ''Diagenetic'' intervals (D1 to D5). Deposition of sapropel S1 was a time of good preservation with variable dissolution and no overgrowth of E. huxleyi coccoliths, whereas calcite overgrowth was high during the Last Glacial Maximum (LGM) and interglacial period and, to a lesser extent, during the Younger Dryas and through the last 5 ka. D

show abstract

“…Sapropels are utilized as analogues for the widespread, high-TOC black shales that characterize the Palaeozoic and Mesozoic Oceanic Anoxic Events 28,29 . Sapropel intervals are relatively thin (1-10 s of cm) compared with many of the Mesozoic black shales (10 s of cm to 10 s of m), and meiofaunal pellets are restricted to the top 3-4 cm of each sapropel due to less severe bottom or pore-water conditions in this upper interval.…”

Section: Discussionmentioning

confidence: 99%

“…The Pliocene sapropels are a classic low-oxygen facies commonly used as an analogue system for the widespread, organic carbon-rich black shales that characterize economically and oceanographically important intervals in the Palaeozoic and Mesozoic 28,29 . We image compositional differences using backscatter electron (BSE) microscopy of ion polished samples to demonstrate that meiofauna pre-dated macrofaunal burrowing, providing a leading edge of irrigation and pelletization in low-oxygen sediments.…”

mentioning

confidence: 99%

Micro-trace fossils reveal pervasive reworking of Pliocene sapropels by low-oxygen-adapted benthic meiofauna

Löhr

Kennedy

2015

Nat Commun

View full text Add to dashboard Cite

Animal burrowers leave an indelible signature on the sedimentary record in most marine environments, with the seeming exception of low-oxygen environments. In modern sedimentary settings, however, sub-millimetre-sized benthic animals (meiofauna) are adapted to low oxygen and even sulfidic conditions. Almost nothing is known about their impact on ancient marine sediments because they leave few recognizable traces. Here we show, in classic Pliocene-aged anoxic facies from the Mediterranean, the first reported trace fossil evidence of meiofaunal activity and its relation to changing oxygenation. A novel approach utilizing electron imaging of ion-polished samples shows that meiofauna pervasively reworked sediment under oxygen-depleted conditions that excluded macrofauna, fragmenting organic laminae and emplacing 15-to 70-mm-diameter faecal pellets without macroscopically influencing the fabric. The extent of reworking raises the question: how pervasively altered are other sediments presently assumed to lack animal influence and how far into the geological record does this influence extend?

show abstract

Neogene sapropels in the Mediterranean: a review

Cited by 225 publications

References 66 publications

The response of Mediterranean thermohaline circulation to climate change: a minimal model

The response of Mediterranean thermohaline circulation to climate change: a minimal model

Abnormal carbonate diagenesis in Holocene–late Pleistocene sapropel-associated sediments from the Eastern Mediterranean; evidence from Emiliania huxleyi coccolith morphology

Micro-trace fossils reveal pervasive reworking of Pliocene sapropels by low-oxygen-adapted benthic meiofauna

Contact Info

Product

Resources

About