The Sadler effect describes variation in apparent sediment accumulation rates and

bed A bed is an item of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many beds ...

thicknesses back through time inherent to the

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

sedimentary record The geologic record in stratigraphy, paleontology and other natural sciences refers to the entirety of the layers of rock strata. That is, deposits laid down by volcanism or by deposition of sediment derived from weathering detritus (clays, sand ...

.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 gr ...

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 Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anima ...

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

Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and '' ...

are much longer than those in the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

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

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

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). It follows the Neogene Period and spans from 2.58 million years ...

, 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 In scientific research, the null hypothesis (often denoted ''H''0) is the claim that no difference or relationship exists between two sets of data or variables being analyzed. The null hypothesis is that any experimentally observed difference is d ...

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 margin ...

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