An age estimation of recent sediments can be found by studying the lead-210 isotope content. This technique is similar to carbon-14 dating and can estimate an age as far back as 150 years. Sediments can also be dated by their remnant magnetism. Sediments are deposited in a lake where they retain minerals such as hematite. Remnant magnetism is caused by the earth's magnetic field, which oscillates about a mean direction with a constant frequency at a given location. Some lake sediments are laid down in distinct layers. When the annual layers are distinguishable, they are called varves. In lakes that have been glacially fed by streams thermal stratification is extremely apparent. It is here that varves permit direct and accurate age determinations.

Some of the conclusions made by discoveries in paleolimnology indicate that the old concepts are not necessarily true. For example the analyses of many chemical and biological remains in sediments indicate that most temperate lakes progressed from oligotrophy to eutrophy. This is a common universal idea. However, it is stated that nutrient loading and productivity were commonly very low after lakes were under the cold boreal conditions that followed glaciation (Wetzel,pg.726). The transition period from tundra to coniferous to deciduous-forested conditions is characterized by high lake productivity. As the land surrounding the lakes had a lack of nutrition from the leaching of the soils and the retainment by forested vegetation, productivity declined and stabilized. As the vegetation of the drainage basin was disturbed by man's activities for agriculture and other purposes, nutrient loading increased, and this resulted in high productivity. In areas where high levels of calcium carbonate were located, drainage basin disturbances increased cation and carbonate loading to recipient lakes. This counteracted the effects of simultaneous loading of important nutrients (ie. Phosphorus) resulting in reduced productivity.

There are sediments in lakes that contain a large amount of organic compounds of biological origins. This is produced by either indigenous plants or within the drainage basin and transported to the lake. Compounds like lipid derivatives, are common not only of terrestrial plants but also of algae and bacteria. Analyses of the amount of these compounds in sediments provide a good start in helping to determine the source of the organic matter in the sediment.

The degradation of plant material provides a by-product of plant pigments, which are often preserved well in sediments. Their composition and remnant concentrations in sediments have been used to interpret past changes in algal communities and productivity. Only specific algal or bacterial groups, hydrocarbons found in plants, synthesize carotenoids. Paleolimnologists have been able to determine information about the time of invasion and development of certain algae and bacteria that do not leave morphological features that are recognizable in fossils and sediments. There have been many paleolimnological studies done to determine past general productivity via the stratigraphy of chlorophyll and carotenoid degradation products in sediments.

Pollen grains are the tiny male reproductive bodies of flowering plants. Their outer shell is indestructible and can survive in certain sediments for tens of thousands of years. In pollen analysis the exines or shells of pollen are taken from the soil and studied underneath the microscope. At this time identification is done according to the distinctive shape and surface of the exine. Once all the information is quantified, the identifications are plotted as curves on a pollen diagram. Fluctuations in the curve for each plant category may indicate signs of climatic changes or forest clearance and crop planting by humans.

Most paleolimnologists look for sediments for preservation of pollen in acidic and poorly aerated peat bogs and lake beds. Here biological decay is impeded and grains go through rapid burial. Cave sediments are also a good place to find useful sediments because of their humidity and constant temperature. Plant pollen and spores are often deposited into lakes in proportion to changes in the composition and quantity of parent plants in or surrounding lakes(Wetzel, pg. 727). Most pollen grains preserve well once they have settled at the bottom of a water system. They can be identified as a species to provide measures of each species in proportion to its density and past population dynamics. Stratigraphy is important when studying paleolimnolgy. Stratigraphy of pollen and spores provide evidence of chronology for vegetational changes in the drainage basin related to changes in temperature, rainfall, soil development, and disturbances cause by the activities of humans. Pollen stratigraphy is used in all comprehensive studies to combine other paleolimnological analyses; changes in the plant communities surrounding a water system influence the nutrient loading characteristics and are reflected in chemical and biological indicators of lake productivity.

The most common algal microfossils preserved in lake sediments are the siliceous frustules of diatoms. For example the cysts or scales of chrysophytes or dinoflagellates. Their stratigraphy has been studied to a great extent because they preserve well, can be identified to species and a lot of their physiological ecology is known. The changes in diatom communities through out the history of lake development have been related to the past changes in nutrient chemistry and salinity due to changes in lake level and climate.

The most widely studied and abundant fossils are the remains of Cladocera, ostracods and midges. These freshwater animals leave identifiable remains of fossilized exoskeletons. Based on known population dynamics and factors that control community composition and species diversity cladoceran communities provide evidence of past environmental conditions. For example, food quality and quantity, competition, and selective predation. Changes in lake water levels can be predicted also. The depletion of oxygen can be predicted and useful in reconstruction of the transition of increased productivity and resulting depletion of oxygen form the hypolimnia of lakes in productive stages.