160:
rock fragments (MRFs) and sedimentary rock fragments (SRFs). If the relative abundances cannot be identified, then the clan name is simply obtained from the QFR triangle. If the relative abundances can be obtained, one must plot the appropriate point in the VRF-MRF-SRF triangle to obtain the clan name. If the point plots in the sedarenite field, one must then normalize all the sedimentary rock fragments to 100% and attempt to find the relative abundances of carbonate rock fragments (CRFs), chert fragments and sandstone fragments (Ss) and shale fragments (Sh). Using this information one must plot the point in the CRF-chert-Ss, Sh triangle and find the appropriate clan name. If the relative abundances of different sedimentary rock fragments cannot be obtained, then the rock is called a sedarenite, subsedarenite or feldspathic sedarenite, respectively.
400:
490:
588:
447:
556:
541:
604:
525:
431:
474:
360:
635:
388:
572:
620:
509:
113:
650:
259:
399:
159:
If the abundances of quartz, feldspars and rock fragments indicate that the rock is a litharenite, a sublitharenite or a feldspathic litharenite, one must then normalize the abundance of rock fragments to 100% and attempt to identify the relative abundances volcanic rock fragments (VRFs), metamorphic
135:
To define the clan name one must normalize the sum of abundances of quartz, feldspars and rock fragments to 100%. This means that other constituents that don't fit in these categories are disregarded. After this, the relative percentages of quartz, feldspars and rock fragments are used to plot the
69:
Folk's philosophy is that the name of a rock must convey as much information as possible without being a complete description. For this, he proposed five important properties of sandstones to use as defining characteristics. These five properties are: grain size, chemically precipitated cements,
155:
in the sample. If there is more plagioclase than there is K-feldspar, the rock is either a plagioclase arkose, a plagioclase subarkose or a lithic plagioclase arkose, respectively. If there is more K-feldspar than there is plagioclase, or if it is too difficult to make a distinction between the
489:
214:
Cements are authigenic minerals precipitated in the pores of clastic rocks. The composition and texture of these cements depends on the chemistry of the water in the pore, the surrounding mineralogy, and the temperature and pressure conditions during cementation.
587:
146:
If the abundances of quartz, feldspars and rock fragments indicate that the rock is an arkose, a subarkose or a lithic arkose, one must then normalize the abundance of feldspars to 100% and attempt to identify the relative abundances of
266:
A recent study of carbonate classification within academia and industry by Lokier and Al
Junaibi (2016) has highlighted a strong decline in the use of the Folk Classification with 89% of classifications employing some form of the
359:
183:
Textural maturity is a property that relates to the amount of mechanical energy input on transported sediments through the abrasive power of currents and tides. It is observed in certain characteristics such as
387:
446:
143:
rock fragments, metaquartzite is always plotted on the Q pole of the QFR diagram along with quartz. Granites and other phaneritic igneous rock fragments are plotted in the F pole of the diagram.
295:
The prefix describing the main (non-matrix) component of the rock immediately precedes the suffix, a second prefix describing a second important component may be tagged on to the front of this.
555:
78:
However, Folk stated that cements and miscellaneous transported constituents are optional categories as they are not always observed. The other three properties should always be mentioned.
430:
524:
473:
192:
of the grains. Folk states that as more mechanical energy is applied to transported sediment, this sediment will pass through the following four stages sequentially:
325:(fossilised fecal pellets). May also be used to describe any pellet under 2 mm in diameter (as peloids are often hard to distinguish from intraclasts after
163:
The name must be as specific as possible and one must try to avoid using broad terms like litharenite or sedarenite if the necessary information is available.
649:
603:
540:
171:
Miscellaneous transported constituents are any grains that do not fall into the categories described by the QFR diagram. These usually include
634:
571:
224:
619:
175:
or fossil fragments. These constituents provide a signature for the observed formation and will help correlating between various samples.
70:
textural maturity, miscellaneous transported constituents, and clan designation. Folk's fivefold name must be in the following format:
508:
172:
74:(Grain size): (chemically precipitated cements) (textural maturity) (miscellaneous transported constituents) (clan designation)
348:
A rock consisting mainly of ooids with some shelly fragments, with a crystalline matrix, would be termed a biooosparite.
199:
Submature stage: The sediment contains less than 5% clay and sand grains are poorly sorted and subangular to subrounded.
393:
Biooosparite with calcitic ooids and sparry calcite cement; Carmel
Formation, Middle Jurassic, of southern Utah, USA.
784:
228:
255:, may be preferred in some instances. Folk classification consists of one or two prefixes followed by a suffix.
202:
Mature stage: The sediment contains little to no clay and sand grains are well sorted but not well rounded.
139:
There are some exceptions when summing the abundances. Due to the difficulty in distinguishing quartz from
675:
670:
268:
252:
120:
As others before him, Folk proposed a classification for sandstones based on the relative abundances of
196:
Immature stage: The sediment contains more than 5% clay and sand grains are poorly sorted and angular.
453:
312:
185:
58:
597:. Note that the odds of being able to distinguish peloids from the surrounding micrite are slim.
724:
112:
761:
205:
Supermature stage: Sediment contains no clay and sand grains are well sorted and well rounded.
501:
Note that some of the dark micrite has started to recrystallize in the left half of the image
751:
720:
457:
374:
244:
46:
740:"The petrographic description of carbonate facies: are we all speaking the same language?"
248:
148:
694:
50:
778:
421:
140:
129:
31:
405:
258:
339:, for example quartz grains or carbonate clasts eroded from the surrounding rocks.
680:
336:
152:
107:
54:
156:
feldspars, the name stays as arkose, subarkose or lithic arkose, respectively.
326:
765:
240:
125:
711:
Folk, R.L. (1959). "Practical
Petrographic Classification of Limestones".
409:
378:
239:
Folk's carbonate rock classification details the relative proportions of
417:
413:
370:
322:
189:
42:
756:
739:
136:
appropriate point on a QFR triangle and obtain the clan designation.
121:
97:
Clayey very fine sandstone: immature fossiliferous plagioclase arkose
81:
The following are examples of rock names using Folk's fivefold name:
94:
Very fine sandstone: chert-cemented submature quartzose phyllarenite
17:
366:
303:
262:
Diagram illustrating Folk's (1959) Carbonate classification scheme
257:
111:
495:
Photomicrograph (PPL) of lithoclasts and skeletal material in an
479:
Photomicrograph (PPL) of lithoclasts and skeletal material in an
227:
circle in a grain. In Folk's classification scheme, one uses the
251:, however the more inclusive although less precise alternative,
683:, similar to the QFR diagram of the Folk classification system.
436:
Bioclasts in an
Ordovician biosparite of southern Ohio, USA.;
132:(R). These are the main poles of the classification diagram.
311:
used to describe biogenetic remnants - for example, shells,
223:
Grain size refers to the diameter of the largest possible
91:
Sandy granule conglomerate: calcitic submature calclithite
85:
Coarse sandstone: calcitic submature micaceous subarkose
416:
sediment and sparry calcite cement in a recrystallized
565:
30:
For folk classification systems in anthropology, see
283:is used if the rock has a crystalline matrix, and
64:
287:if it contains a micritic, or mud-based, matrix.
738:Lokier, Stephen W.; Al Junaibi, Mariam (2016).
247:. The classification scheme covers most common
116:QFR diagram for Folk's sandstone classification
45:, is a technical descriptive classification of
365:Thin-section of a biooosparite with calcitic
8:
725:10.1306/0BDA5C36-16BD-11D7-8645000102C1865D
609:Photomicrograph (PPL) of a stromatoporoid
534:from the Silurian Keel Formation, Oklahoma
755:
231:to find the appropriate grain size name.
88:Fine sandstone: supermature quartzarenite
65:Folk's sandstone (clastic) classification
234:
703:
469:
355:
167:Miscellaneous transported constituents
460:, Ohio) showing coarse sparry cement.
7:
593:Photomicrograph (PPL) of a possible
25:
648:
633:
618:
602:
586:
570:
554:
539:
523:
507:
488:
472:
445:
429:
398:
386:
358:
699:(pdf), Austin (Texas), Hemphill
302:used to denote the presence of
235:Folk's carbonate classification
27:Sedimentary rock classification
696:Petrology of Sedimentary Rocks
420:shell; Bird Spring Formation (
57:and Professor Emeritus at the
1:
408:of a biopelsparite showing a
53:, an influential sedimentary
530:Photomicrograph (PPL) of an
514:Photomicrograph (PPL) of an
243:in the rock and the type of
659:(and dolomitized) limestone
655:Photomicrograph (PPL) of a
640:Photomicrograph (PPL) of a
625:Photomicrograph (PPL) of a
577:Photomicrograph (PPL) of a
561:Photomicrograph (PPL) of a
546:Photomicrograph (PPL) of a
801:
424:) of southern Nevada, USA.
321:describes the presence of
105:
29:
412:structure consisting of
381:, of southern Utah, USA.
335:denotes the presence of
676:Gazzi-Dickinson method
263:
117:
671:Dunham classification
269:Dunham classification
261:
253:Dunham classification
115:
466:Thin Section Gallery
454:Brassfield Formation
313:echinoderm ossicles
59:University of Texas
39:Folk classification
693:Folk, R.L. (1980)
452:Broken surface of
352:Components Gallery
264:
118:
785:Sedimentary rocks
757:10.1111/sed.12293
179:Textural maturity
47:sedimentary rocks
16:(Redirected from
792:
770:
769:
759:
750:(7): 1843–1885.
735:
729:
728:
708:
652:
637:
622:
606:
590:
574:
558:
543:
527:
511:
492:
476:
449:
433:
402:
390:
375:Carmel Formation
362:
102:Clan designation
21:
800:
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425:
403:
394:
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382:
363:
354:
346:
293:
277:
249:carbonate rocks
237:
229:Wentworth scale
221:
219:Grain size name
212:
181:
169:
110:
104:
67:
35:
28:
23:
22:
15:
12:
11:
5:
798:
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788:
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730:
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689:
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673:
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657:recrystallized
654:
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632:
630:
627:lime mudstone.
624:
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615:
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592:
585:
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576:
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567:
560:
553:
551:
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529:
522:
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506:
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494:
487:
485:
478:
471:
467:
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463:
462:
458:Early Silurian
451:
444:
442:
440:E = echinoderm
438:T = trilobite;
435:
428:
426:
404:
397:
395:
392:
385:
383:
364:
357:
353:
350:
345:
342:
341:
340:
330:
316:
315:or other tests
306:
292:
289:
276:
273:
236:
233:
220:
217:
211:
208:
207:
206:
203:
200:
197:
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173:heavy minerals
168:
165:
130:rock fragments
103:
100:
99:
98:
95:
92:
89:
86:
76:
75:
66:
63:
51:Robert L. Folk
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
797:
786:
783:
782:
780:
767:
763:
758:
753:
749:
745:
744:Sedimentology
741:
734:
731:
726:
722:
718:
714:
713:AAPG Bulletin
707:
704:
698:
697:
692:
691:
687:
682:
679:
677:
674:
672:
669:
668:
664:
658:
651:
646:
643:
636:
631:
628:
621:
616:
612:
605:
600:
596:
589:
584:
580:
573:
568:
564:
557:
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549:
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537:
533:
526:
521:
517:
510:
505:
502:
498:
491:
486:
482:
475:
470:
465:
459:
455:
448:
443:
432:
427:
423:
422:Carboniferous
419:
415:
411:
407:
401:
396:
389:
384:
380:
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372:
368:
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178:
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166:
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157:
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150:
144:
142:
141:metaquartzite
137:
133:
131:
127:
123:
114:
109:
101:
96:
93:
90:
87:
84:
83:
82:
79:
73:
72:
71:
62:
60:
56:
52:
48:
44:
40:
33:
32:Folk taxonomy
19:
747:
743:
733:
716:
712:
706:
695:
656:
641:
626:
610:
594:
578:
562:
547:
531:
515:
500:
497:intramicrite
496:
481:intrasparite
480:
406:Thin section
347:
332:
318:
308:
299:
294:
284:
280:
278:
265:
238:
222:
213:
182:
170:
162:
158:
145:
138:
134:
119:
80:
77:
68:
38:
36:
719:(1): 1–38.
681:QFL Diagram
369:and sparry
337:intraclasts
279:The suffix
153:plagioclase
149:K-feldspars
108:QFL diagram
55:petrologist
49:devised by
688:References
642:dismicrite
611:boundstone
595:pelmicrite
579:pelsparite
563:biomicrite
548:biosparite
327:diagenesis
106:See also:
766:1365-3091
532:oomicrite
516:oosparite
377:, Middle
241:allochems
225:inscribed
128:(F), and
126:feldspars
779:Category
665:See also
410:geopetal
379:Jurassic
373:cement;
291:Prefixes
285:-micrite
281:-sparite
275:Suffixes
271:system.
186:rounding
418:bivalve
371:calcite
344:Example
323:peloids
210:Cements
190:sorting
43:geology
764:
414:peloid
333:intra-
245:matrix
122:quartz
367:ooids
304:ooids
124:(Q),
41:, in
762:ISSN
319:pel-
309:bio-
188:and
37:The
752:doi
721:doi
499:.
300:oo-
151:to
18:QFR
781::
760:.
748:63
746:.
742:.
717:43
715:.
581:.
61:.
768:.
754::
727:.
723::
613:.
518:.
483:.
456:(
329:)
34:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
