Some notes on sample location selection and collecting dose rate samples

Sample submittal sheet

sample sumittal sheet guide

Gamma rays can travel 30 cm in any direction from their emitting nucleus and thus can influence the gamma dose rate that makes up part of the total annual dose rate used in the final age calculation for luminescence ages from 30 cm away from a sample. For dose rate samples, take a representative sample for 30 cm in all directions even if it is in a different horizon.  For example, if your sample horizon is only 10 cm thick, and over/underlain by another unit, you would want to collect a bit of dose rate sample from the sample horizon and from the over/underlying ones. In practice, this can be a good guide for selecting a sample site.  It is best and easiest to sample in the middle of a unit that is at least 60 cm thick (or the same unit for a 60 cm sphere (that's about 24 inches) with the sample in the middle if there is un-level stratigraphy) so there aren't problems with complex dosimetry.  If the site has unavoidable complex geometry, an in situ gamma dose measurement should be taken using a portable NaI detector or the like. 

Rule of thumb: Select sample locations that are at least about 2 feet thick or the same composition for a foot sphere to avoid complex dosimetry.

 

Sampling from vertical exposures

Supplies:

·  Sample tubes (gray or black 3 mm (1/8 in) thick, 6 cm (2.25 in) diameter, plastic electrical conduit cut to 30 cm (12 in) lengths.  

·  5 pound sledge

·  Pipe end cap

·  Sample info/submittal sheet

·  Black plastic

·  Newspaper (or some kind of stopper material that will fit snugly into the tube)

·  Masking tape (DO NOT use duct tape or other slick tape—ink rubs off of it too easily!)

·  Black Sharpies (DO NOT use red or orange.  They are invisible in the lab.)

·  Clear sample bags

(Alternative supplies may be used, for example: opaque metal conduit of a similar size, AMS slide hammer corer and fitted metal sample tubes).  

Clean a fresh face.  Choose a sample location that is homogenous within a 30 cm radius.  

Put newspaper or some kind of stopper material into the tube flush with the end that will first be pushed into the face.  The stopper will move toward the outside end of the tube with the sample.  This procedure is intended to prevent collapse of loose material inside the tube as the tube is pushed into the face.  Put the pipe cap on the outside end of the tube away from the face. You can use a piece of tape to keep the cap on the tube while hammering in and later digging it out.

Place the tube against the sample surface and use 5 lb sledge to hammer into the face.  Hammer the tube in perpendicular to the face.  Hammer the tube in until refusal when the tube is filled and the outer end of the tube reaches the face.

If you are collecting more than one sample in vertical succession (recommend at least 2 in a vertical sequence) put in all tubes bottom to top, and then dig out bottom to top.  

Dig the sample tube out being careful not to shift the sediment inside.  If the tube is not filled, stuff paper or stopper material in to take up any extra space in the tube and keep the sediment packed tight.

Tape both ends of the sample tube with 2 layers of black plastic.  Make any notes about the sample on the tape--not on the plastic. 

Record information about the sample on the Sample Submittal Sheet.

Indicate the direction the tube was pushed into the face with an arrow.  The arrow should point to the leading end of the tube that was pushed into the face. 

Collect a sample for environmental dose rate that includes representative material from a 30 cm radius around the luminescence sample.  This sample should be labeled ‘dose rate’ and the same id name/number as the luminescence sample.  This sample needn’t be light tight.  Preferably, fold the closed zipper edge over and tape down the seal, folding tape around the entirety of the sample. Record the sample id on the tape rather than the bag (ink rubs off the bags easily).   


 

Auger sampling

Supplies

·  Sample tubes (gray or black 3 mm (1/8 in) thick, 6 cm (2.25 in) diameter, plastic electrical conduit cut to 30 cm (12 in) lengths with holes drilled to match the alignment of the sample tube adapter auger head (contact DRILL for these tubes).  

·  2 3/4” telescoping or other auger

·  Sample tube adapter auger head and bolt—may be checked out from DRILL.  Fits an AMS telescoping auger extension with 1 inch inside diameter OR an AMS signature threaded auger extension.

·  Snapper pin (1/4" x 2") or similar sized bolt and wing nut

·  Sample info/submittal sheet

·  Black plastic

·  Newspaper (or some kind of stopper/stuffing material)

·  Masking tape (DO NOT use duct tape or other slick tape—ink rubs off of it too easily!)

·  Black Sharpies (DO NOT use red or orange.  They are invisible in the lab.)

·  Clear sample bags

Using a telescoping auger and a regular auger head, auger to the depth that you want to sample bearing in mind that depending on the cohesion of the sediment, the hole may collapse inward. 

For the material removed from the auger hole in the auger just before the sample, remove the ~ 2 inches of material from the end of the auger and place into a clear plastic bag. This is the dose rate sample and needn’t be light tight.  You will add more to this sample after collecting the luminescence sample.   

Attach the sample tube adapter to the auger extension stem using a quick release snapper pin. 

Insert the non-beveled end of the sample tube with the two holes into the adapter and line up the sample tube holes with the holes on the adapter.

Insert the long bolt across the holes in the tube and adapter to secure them together and fasten the wing nut on the end. 

Have two layers of black plastic and tape ready to cover the end of the sample when you bring it up out of the hole. 

Collect the luminescence sample, being sure to turn and push the auger down until you meet refusal. 

Quickly reverse the turn of the auger and bring the auger up out of the hole.

Have a helper place the black plastic over the end of the tube as soon as it reaches the surface. 

Feel to check that the tube is to the end.  If not, stuff paper or stopper material in to take up any extra space in the tube and keep the sediment packed tight. Tape the 2 layers of black plastic to the tube.   

Again, have 2 layers of black plastic at hand.  Remove the bolt from the sample tube and adapter and remove the tube from the adapter putting the black plastic over the tube immediately.  Feel to check that the tube is full. If not, stuff paper or stopper material in to take up any extra space in the tube and keep the sediment packed tight. Using masking tape, affix the 2 layers of black plastic over the end of the tube.   

Make any notes or labeling about the sample on the masking tape--not on the plastic (ink will rub off of the plastic). 

Record the information about the sample on the Sample Submittal Sheet.

Indicate the direction the tube was pushed into the face with an arrow.  The arrow should point to the leading end of the tube that was pushed into the face. 

Switch the auger head to a regular auger head. 

Auger down the hole again and bring up a few more inches of sample material. 

This sample should be from the few inches just below the luminescence sample collected.  Put this material in the clear plastic bag with the sediment you collected from just above the sample. 

This sample is for environmental dose rate and should include representative material from a 30 cm radius around the luminescence sample. If the sample is not very deep, collect some material from the side walls of the tube that would be adjacent to the luminescence sample and add it to the clear bag.

This sample should be labeled ‘dose rate’ and the same id name/number as the luminescence sample. This sample needn’t be light tight.  Preferably, fold the closed zipper edge over and tape down the seal, folding tape around the entirety of the sample. Record the sample id on the tape rather than the bag (ink rubs off the bags easily).