Also referred to by some older web pages as “Limestone Canyon Reserve”.  Limestone Canyon is part of the approximately 50,000 acre Irvine Ranch Natural Landmarks in Orange County CA.  Historically Limestone Canyon was once part of the vast Irvine Ranch.  The ranch stretched for miles from about the 91 freeway all the way to the ocean at the Crystal Cove State Park (beach) area.  The Irvine Ranch lands were the first to receive the California Natural Landmark designation.   Limestone Canyon is home to four major ecosystems:  Oak woodland, riparian, coastal scrub and grasslands.  A diverse range of native plants and animals are found in the canyon.  Horned lizards, mountain lions, bobcats, deer, coyotes, rattlesnakes, ring-tails and a variety of birds are on the list of wildlife found here.  The canyon includes two popular geological features:  the “Sinks” (often compared to a mini Grand Canyon) and “Dripping Springs” (spring water dripping out of an earthquake fault down a fern covered rock face). Limestone Canyon has miles of trails for equestrian use (bring your own horse), mountain biking and hiking but access is by sign up/group events only to protect this beautiful resource, click here and then follow the “activities” link for the guided access schedule.  Trail map hand outs are provided the day of the activity upon sign in.  See the “external links” section at the end of this page for more information about Limestone Canyon and the Irvine Ranch Natural Landmarks.  Click any picture below to enlarge.

Mule Deer on Dripping Springs Trail

Deer track on the right, Bobcat track on the left. The fourth toe is smeared into the pad imprint.

Dripping Springs, 10-26-05

Pool at the base of Dripping Springs rock face, 10/26/05 "Dripping Springs" is a natural spring seeping from an earthquake fault down a rock face into a pool at the base.  The rock face is alive with fern and water loving plants.  This area is accessible by guided hike only for preservation purposes.

Limestone Canyon blooms, pics dated 3/3/12.  From left to right, unidentified native plant, Blue-Eyed Grass and Our Lords Candle. 

External Links: Fun Orange County Parks, excellent write up of Limestone Canyon including facts, links, photos, and tips about visiting Limestone Canyon: http://www.funorangecountyparks.com/2011/02/irvine-ranch-natural-landmarks.html California plant identification, pictures helpful in identifying both native and non native plants found in Orange County: http://nathistoc.bio.uci.edu/plants/index.htm This link includes common OC wildlife and everything else: http://nathistoc.bio.uci.edu/index.htm Bobcat & deer tracks, photo ID guide:  http://www.bear-tracker.com/bobcat.html

Irvine Ranch Natural Landmarks website
Watch the video about the land here:  http://www.irlandmarks.org/About/Video.aspx
Information and lands map here:  http://www.irlandmarks.org/

Limestone Canyon Educational Workbook
An older document written for middle school students (pre-natural landmark days) with some interesting facts:  http://www.eastoforange.com/education/limestone_workbook.pdf

City of Irvine’s Open Space Program
http://www.ci.irvine.ca.us/civica/filebank/blobdload.asp?BlobID=12956

LA Times article on Limestone Canyon, dated December 2004, mentions a little about the geological features of Limestone Canyon
http://articles.latimes.com/2004/dec/28/news/os-sinks28

An older write up (pre-natural landmark days) of “Limestone Canyon Reserve”, refers to Canyon historical fact, long ago a cement making operation mined limestone, hence the name “Limestone Canyon”:  http://www.hike-oc.com/limestone_canyon.html 

Good list of Orange County wild lands, information and links, on the Orange County Wild website—interesting fact from OC Wild:  Orange County is the second most biologically diverse county in California while at the same time the smallest and most densely populated—see the “about” page on the link below for more facts:
http://www.orangecountywild.com/

A good write up by Brian & Ashley’s Hiking Blog on the newer Limestone Canyon Shoestring Trail:  http://abhiking.blogspot.com/2011/08/limestone-canyon-wilderness-park.html

Another good Brian & Ashley’s Hiking Blog write up on the Sinks.  This write up contains very good directions to Limestone Canyon’s trailheads and points out the fact there are two, the Augustine Staging Area and the Portela Springs Staging Area (in case you ever want to visit and haven’t been there) plus links to sign up for a hike:  http://abhiking.blogspot.com/2011/03/limestone-canyon-wilderness-viewing.html

Also see Irvine Ranch Conservancy:
http://www.irconservancy.com/