The Sadler effect describes variation in apparent sediment accumulation rates and bed thicknesses back through time inherent to the

geological Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

sedimentary record.Sadler, Peter M. "Sediment accumulation rates and the completeness of stratigraphic sections." The Journal of Geology (1981): 569–584.Peter Sadler
analysed what structure you would expect in a

stratigraphic section A stratigraphic section is a sequence of layers of rocks in the order they were deposited. It is based on the principle of original horizontality, which states that layers of sediment are originally deposited horizontally under the action of ...

under the hypothesis that bigger geological events – episodes of deposition, erosion, and the gaps between those events – are rarer. He showed that under these conditions it is inevitable that, on average, thinner stratigraphic sections, which cover shorter amounts of time, record faster accumulation rates than thicker sections, which record longer amounts of time.Schumer, Rina, Douglas Jerolmack, and Brandon McElroy. "The stratigraphic filter and bias in measurement of geologic rates." Geophysical Research Letters 38.11 (2011): L11405.Schumer, Rina, and Douglas J. Jerolmack. "Real and apparent changes in sediment deposition rates through time." Journal of Geophysical Research: Earth Surface (2003–2012) 114.F3 (2009). The effect equivalently states that more ancient packages of sediment in the stratigraphic record will record slower sedimentation rates stretched over longer periods of time. For instance, it explains the fact that in general, the more ancient geological periods of the

Phanerozoic The Phanerozoic is the current and the latest of the four eon (geology), geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and ...

are longer than the more recent ones; i.e., the periods of the

Palaeozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of ...

are much longer than those in the

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

. Conversely, it also explains that the maximum sediment accumulation rates seen in the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

at the start of the Phanerozoic are almost two orders of magnitude lower than those observed in the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

, at its end. The Sadler effect provides a powerful framework for understanding how information extracted from any given stratigraphic section differs from what should be expected under constant conditions – that is, it provides a

null hypothesis The null hypothesis (often denoted ''H''0) is the claim in scientific research that the effect being studied does not exist. The null hypothesis can also be described as the hypothesis in which no relationship exists between two sets of data o ...

for analysing stratigraphy. It also provides techniques to estimate the completeness of a given stratigraphic section on a given timescale. Sections are less complete at shorter timescales, which means that at sufficiently short timescales and for some purposes, some sedimentary successions may contain essentially no useful information. For example, the Sadler effect has since been used to investigate whether apparent increases in global sedimentation rates across the last 5 Ma are real; how we might read the record of sediments deposited on

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...

s;Jerolmack, Douglas J., and Peter Sadler. "Transience and persistence in the depositional record of continental margins." Journal of Geophysical Research: Earth Surface (2003–2012) 112.F3 (2007). to interpret fluvial processes such as river avulsion; and to understand what information, and which processes at what timescales, can be preserved in sediments.Jerolmack, Douglas J., and Chris Paola. "Shredding of environmental signals by sediment transport." Geophysical Research Letters 37.19 (2010).

References

{{Geologic Principles, state=collapsed Sedimentology Earth sciences Physical geography

See also

References