TYPES OF SAMPLES

There are several types of samples stored at the LDCR. The majority of our collection are Sediment Cores which are tubes of "mud" that can be collected from different environments: lakes, rivers, wetlands, seas and oceans. There are many types of sediment cores; which one used depends on the environment to be cored and the research goals of the project: piston, gravity, trigger-weight, kasten, box, multi-, push, vibra-, drill. Regardless of the type or location, sediment cores are a record of environmental changes through time. 

In addition to sediment cores, other types of samples in our collection include Grabs (surface sediments are 'grabbed' using a variety of devices) and Dredges (a large bag made of metal chain links is lowered to the surface and dragged along the ocean/lake/river floor to collect rocks and gravel).

 

TYPES OF CORES

There are many different types of coring mechanisms. Listed below are only some of the main types and there are variations of almost all of them. Gravity, Trigger-Weight and Piston Corers consist of PVC (or other plastic) pipes inside metal sleeves with weights on top and the samples they retrieve make up the majority of most soft-sediment core collections.

GRAVITY CORES - A Gravity Corer is a very simple design: an empty core barrel with weights on top and a 'core catcher' in the bottom. It is lowered from a ship and allowed to free-fall into soft sediments; the weights on top driving the barrel into the "mud". The core catcher in the bottom is a type of one-way valve that allows sediments into the coring barrel and closes when the core is being hauled up to the ship. They can be used in almost any water depth and retrieve samples of up to 12 meters length.

KASTEN CORES - A Kastenlot Corer is, essentially, a gravity corer but with a square barrel. However, instead of needing to be mechanically split open like most other cores, half of the Kasten Core barrel can be removed allowing for quick and easy access to the sediments within. They can be used in almost any water depth and retrieve samples of up to 12 meters length.

TRIGGER-WEIGHT CORES - A Trigger-Weight Corer is a small gravity core with minimal weight on top. They are used in conjunction with piston corers to trigger the free-fall of the piston corer and to capture the upper sediments in a coring location. They are usually up to 3 meters in length. NOTE: the majority of Trigger-Weight Cores in the LDCR collection are extremely small: only 3cm in diameter and up to 50cm in length.

PISTON CORES - A Piston Corer is a gravity corer with a piston mechanism inside the coring barrel which allows for longer cores to be taken. After the apparatus hits the sediment surface, the piston is slowly pulled up inside the coring barrel, creating a weak vacuum. This allows more sediment to be pulled into the coring barrel. They are used in deeper waters (as shallow as 50m) and can retrieve samples as long as 30 meters. In many instances, Piston Cores "overpenetrate" the sediments they are coring (due to their heavier weight), losing the uppermost layers. To capture the uppermost sediments and correlate them with the piston core, a Trigger-Weight Core is taken alongside a Piston Core.

BOX CORES - A Box Corer samples a large, relatively shallow surface area: up to 50cm x 50cm, and a depth of 60cm. The resulting sample must then be sub-sampled before the device can be used again. Sub-sampling box cores can be done by pushing plastic tubes into the mud (resulting in small cores), by slabbing or other means determined by the PI.

MULTI-CORES - A Multi-Corer allows for multiple, shallow cores (~60cm in length) to be taken at the same time. They have spring-loaded lids on the top and bottom that close as the mechanism is brought back up to the ship. Multi-Cores are useful for capturing the sediment-water interface.

VIBRACORES - A Vibracorer is used to penetrate sandy sediments that a gravity or piston corer cannot. Motors vibrate the barrel as it penetrates the sediments allowing for collection of cores up to 12 meters in length.

PUSH CORES - A Push Corer is a small tube that is simply pushed into the sediment. In marine realms, they are one type of sample taken with ROVs.

DRILL CORES - Drill Coring is used on land to retrieve rock cores as well as in other environments where sediments have become extremely lithified and cannot be penetrated by other types of coring.